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[FreeBSD/FreeBSD.git] / sys / kern / sched_ule.c

/*-
 * Copyright (c) 2002-2007, Jeffrey Roberson <jeff@freebsd.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice unmodified, this list of conditions, and the following
 *    disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include "opt_hwpmc_hooks.h"
#include "opt_sched.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kdb.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/resource.h>
#include <sys/resourcevar.h>
#include <sys/sched.h>
#include <sys/smp.h>
#include <sys/sx.h>
#include <sys/sysctl.h>
#include <sys/sysproto.h>
#include <sys/turnstile.h>
#include <sys/umtx.h>
#include <sys/vmmeter.h>
#ifdef KTRACE
#include <sys/uio.h>
#include <sys/ktrace.h>
#endif

#ifdef HWPMC_HOOKS
#include <sys/pmckern.h>
#endif

#include <machine/cpu.h>
#include <machine/smp.h>

#ifndef PREEMPTION
#error  "SCHED_ULE requires options PREEMPTION"
#endif

/*
 * TODO:
 *      Pick idle from affinity group or self group first.
 *      Implement pick_score.
 */

#define KTR_ULE 0x0             /* Enable for pickpri debugging. */

/*
 * Thread scheduler specific section.
 */
struct td_sched {       
        TAILQ_ENTRY(td_sched) ts_procq; /* (j/z) Run queue. */
        int             ts_flags;       /* (j) TSF_* flags. */
        struct thread   *ts_thread;     /* (*) Active associated thread. */
        u_char          ts_rqindex;     /* (j) Run queue index. */
        int             ts_slptime;
        int             ts_slice;
        struct runq     *ts_runq;
        u_char          ts_cpu;         /* CPU that we have affinity for. */
        /* The following variables are only used for pctcpu calculation */
        int             ts_ltick;       /* Last tick that we were running on */
        int             ts_ftick;       /* First tick that we were running on */
        int             ts_ticks;       /* Tick count */
#ifdef SMP
        int             ts_rltick;      /* Real last tick, for affinity. */
#endif

        /* originally from kg_sched */
        u_int   skg_slptime;            /* Number of ticks we vol. slept */
        u_int   skg_runtime;            /* Number of ticks we were running */
};
/* flags kept in ts_flags */
#define TSF_BOUND       0x0001          /* Thread can not migrate. */
#define TSF_XFERABLE    0x0002          /* Thread was added as transferable. */

static struct td_sched td_sched0;

/*
 * Cpu percentage computation macros and defines.
 *
 * SCHED_TICK_SECS:     Number of seconds to average the cpu usage across.
 * SCHED_TICK_TARG:     Number of hz ticks to average the cpu usage across.
 * SCHED_TICK_MAX:      Maximum number of ticks before scaling back.
 * SCHED_TICK_SHIFT:    Shift factor to avoid rounding away results.
 * SCHED_TICK_HZ:       Compute the number of hz ticks for a given ticks count.
 * SCHED_TICK_TOTAL:    Gives the amount of time we've been recording ticks.
 */
#define SCHED_TICK_SECS         10
#define SCHED_TICK_TARG         (hz * SCHED_TICK_SECS)
#define SCHED_TICK_MAX          (SCHED_TICK_TARG + hz)
#define SCHED_TICK_SHIFT        10
#define SCHED_TICK_HZ(ts)       ((ts)->ts_ticks >> SCHED_TICK_SHIFT)
#define SCHED_TICK_TOTAL(ts)    (max((ts)->ts_ltick - (ts)->ts_ftick, hz))

/*
 * These macros determine priorities for non-interactive threads.  They are
 * assigned a priority based on their recent cpu utilization as expressed
 * by the ratio of ticks to the tick total.  NHALF priorities at the start
 * and end of the MIN to MAX timeshare range are only reachable with negative
 * or positive nice respectively.
 *
 * PRI_RANGE:   Priority range for utilization dependent priorities.
 * PRI_NRESV:   Number of nice values.
 * PRI_TICKS:   Compute a priority in PRI_RANGE from the ticks count and total.
 * PRI_NICE:    Determines the part of the priority inherited from nice.
 */
#define SCHED_PRI_NRESV         (PRIO_MAX - PRIO_MIN)
#define SCHED_PRI_NHALF         (SCHED_PRI_NRESV / 2)
#define SCHED_PRI_MIN           (PRI_MIN_TIMESHARE + SCHED_PRI_NHALF)
#define SCHED_PRI_MAX           (PRI_MAX_TIMESHARE - SCHED_PRI_NHALF)
#define SCHED_PRI_RANGE         (SCHED_PRI_MAX - SCHED_PRI_MIN + 1)
#define SCHED_PRI_TICKS(ts)                                             \
    (SCHED_TICK_HZ((ts)) /                                              \
    (roundup(SCHED_TICK_TOTAL((ts)), SCHED_PRI_RANGE) / SCHED_PRI_RANGE))
#define SCHED_PRI_NICE(nice)    (nice)

/*
 * These determine the interactivity of a process.  Interactivity differs from
 * cpu utilization in that it expresses the voluntary time slept vs time ran
 * while cpu utilization includes all time not running.  This more accurately
 * models the intent of the thread.
 *
 * SLP_RUN_MAX: Maximum amount of sleep time + run time we'll accumulate
 *              before throttling back.
 * SLP_RUN_FORK:        Maximum slp+run time to inherit at fork time.
 * INTERACT_MAX:        Maximum interactivity value.  Smaller is better.
 * INTERACT_THRESH:     Threshhold for placement on the current runq.
 */
#define SCHED_SLP_RUN_MAX       ((hz * 5) << SCHED_TICK_SHIFT)
#define SCHED_SLP_RUN_FORK      ((hz / 2) << SCHED_TICK_SHIFT)
#define SCHED_INTERACT_MAX      (100)
#define SCHED_INTERACT_HALF     (SCHED_INTERACT_MAX / 2)
#define SCHED_INTERACT_THRESH   (30)

/*
 * tickincr:            Converts a stathz tick into a hz domain scaled by
 *                      the shift factor.  Without the shift the error rate
 *                      due to rounding would be unacceptably high.
 * realstathz:          stathz is sometimes 0 and run off of hz.
 * sched_slice:         Runtime of each thread before rescheduling.
 */
static int sched_interact = SCHED_INTERACT_THRESH;
static int realstathz;
static int tickincr;
static int sched_slice;

/*
 * tdq - per processor runqs and statistics.
 */
struct tdq {
        struct runq     tdq_idle;               /* Queue of IDLE threads. */
        struct runq     tdq_timeshare;          /* timeshare run queue. */
        struct runq     tdq_realtime;           /* real-time run queue. */
        u_char          tdq_idx;                /* Current insert index. */
        u_char          tdq_ridx;               /* Current removal index. */
        short           tdq_flags;              /* Thread queue flags */
        int             tdq_load;               /* Aggregate load. */
#ifdef SMP
        int             tdq_transferable;
        LIST_ENTRY(tdq) tdq_siblings;           /* Next in tdq group. */
        struct tdq_group *tdq_group;            /* Our processor group. */
#else
        int             tdq_sysload;            /* For loadavg, !ITHD load. */
#endif
};

#define TDQF_BUSY       0x0001                  /* Queue is marked as busy */

#ifdef SMP
/*
 * tdq groups are groups of processors which can cheaply share threads.  When
 * one processor in the group goes idle it will check the runqs of the other
 * processors in its group prior to halting and waiting for an interrupt.
 * These groups are suitable for SMT (Symetric Multi-Threading) and not NUMA.
 * In a numa environment we'd want an idle bitmap per group and a two tiered
 * load balancer.
 */
struct tdq_group {
        int     tdg_cpus;               /* Count of CPUs in this tdq group. */
        cpumask_t tdg_cpumask;          /* Mask of cpus in this group. */
        cpumask_t tdg_idlemask;         /* Idle cpus in this group. */
        cpumask_t tdg_mask;             /* Bit mask for first cpu. */
        int     tdg_load;               /* Total load of this group. */
        int     tdg_transferable;       /* Transferable load of this group. */
        LIST_HEAD(, tdq) tdg_members;   /* Linked list of all members. */
};

#define SCHED_AFFINITY_DEFAULT  (hz / 100)
#define SCHED_AFFINITY(ts)      ((ts)->ts_rltick > ticks - affinity)

/*
 * Run-time tunables.
 */
static int rebalance = 0;
static int pick_pri = 1;
static int affinity;
static int tryself = 1;
static int tryselfidle = 1;
static int ipi_ast = 0;
static int ipi_preempt = 1;
static int ipi_thresh = PRI_MIN_KERN;
static int steal_htt = 1;
static int steal_busy = 1;
static int busy_thresh = 4;

/*
 * One thread queue per processor.
 */
static volatile cpumask_t tdq_idle;
static volatile cpumask_t tdq_busy;
static int tdg_maxid;
static struct tdq       tdq_cpu[MAXCPU];
static struct tdq_group tdq_groups[MAXCPU];
static int bal_tick;
static int gbal_tick;
static int balance_groups;

#define TDQ_SELF()      (&tdq_cpu[PCPU_GET(cpuid)])
#define TDQ_CPU(x)      (&tdq_cpu[(x)])
#define TDQ_ID(x)       ((x) - tdq_cpu)
#define TDQ_GROUP(x)    (&tdq_groups[(x)])
#else   /* !SMP */
static struct tdq       tdq_cpu;

#define TDQ_SELF()      (&tdq_cpu)
#define TDQ_CPU(x)      (&tdq_cpu)
#endif

static void sched_priority(struct thread *);
static void sched_thread_priority(struct thread *, u_char);
static int sched_interact_score(struct thread *);
static void sched_interact_update(struct thread *);
static void sched_interact_fork(struct thread *);
static void sched_pctcpu_update(struct td_sched *);
static inline void sched_pin_td(struct thread *td);
static inline void sched_unpin_td(struct thread *td);

/* Operations on per processor queues */
static struct td_sched * tdq_choose(struct tdq *);
static void tdq_setup(struct tdq *);
static void tdq_load_add(struct tdq *, struct td_sched *);
static void tdq_load_rem(struct tdq *, struct td_sched *);
static __inline void tdq_runq_add(struct tdq *, struct td_sched *, int);
static __inline void tdq_runq_rem(struct tdq *, struct td_sched *);
void tdq_print(int cpu);
static void runq_print(struct runq *rq);
#ifdef SMP
static int tdq_pickidle(struct tdq *, struct td_sched *);
static int tdq_pickpri(struct tdq *, struct td_sched *, int);
static struct td_sched *runq_steal(struct runq *);
static void sched_balance(void);
static void sched_balance_groups(void);
static void sched_balance_group(struct tdq_group *);
static void sched_balance_pair(struct tdq *, struct tdq *);
static void sched_smp_tick(struct thread *);
static void tdq_move(struct tdq *, int);
static int tdq_idled(struct tdq *);
static void tdq_notify(struct td_sched *);
static struct td_sched *tdq_steal(struct tdq *, int);

#define THREAD_CAN_MIGRATE(td)   ((td)->td_pinned == 0)
#endif

static void sched_setup(void *dummy);
SYSINIT(sched_setup, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, sched_setup, NULL)

static void sched_initticks(void *dummy);
SYSINIT(sched_initticks, SI_SUB_CLOCKS, SI_ORDER_THIRD, sched_initticks, NULL)

static inline void
sched_pin_td(struct thread *td)
{
        td->td_pinned++;
}

static inline void
sched_unpin_td(struct thread *td)
{
        td->td_pinned--;
}

static void
runq_print(struct runq *rq)
{
        struct rqhead *rqh;
        struct td_sched *ts;
        int pri;
        int j;
        int i;

        for (i = 0; i < RQB_LEN; i++) {
                printf("\t\trunq bits %d 0x%zx\n",
                    i, rq->rq_status.rqb_bits[i]);
                for (j = 0; j < RQB_BPW; j++)
                        if (rq->rq_status.rqb_bits[i] & (1ul << j)) {
                                pri = j + (i << RQB_L2BPW);
                                rqh = &rq->rq_queues[pri];
                                TAILQ_FOREACH(ts, rqh, ts_procq) {
                                        printf("\t\t\ttd %p(%s) priority %d rqindex %d pri %d\n",
                                            ts->ts_thread, ts->ts_thread->td_proc->p_comm, ts->ts_thread->td_priority, ts->ts_rqindex, pri);
                                }
                        }
        }
}

void
tdq_print(int cpu)
{
        struct tdq *tdq;

        tdq = TDQ_CPU(cpu);

        printf("tdq:\n");
        printf("\tload:           %d\n", tdq->tdq_load);
        printf("\ttimeshare idx: %d\n", tdq->tdq_idx);
        printf("\ttimeshare ridx: %d\n", tdq->tdq_ridx);
        printf("\trealtime runq:\n");
        runq_print(&tdq->tdq_realtime);
        printf("\ttimeshare runq:\n");
        runq_print(&tdq->tdq_timeshare);
        printf("\tidle runq:\n");
        runq_print(&tdq->tdq_idle);
#ifdef SMP
        printf("\tload transferable: %d\n", tdq->tdq_transferable);
#endif
}

static __inline void
tdq_runq_add(struct tdq *tdq, struct td_sched *ts, int flags)
{
#ifdef SMP
        if (THREAD_CAN_MIGRATE(ts->ts_thread)) {
                tdq->tdq_transferable++;
                tdq->tdq_group->tdg_transferable++;
                ts->ts_flags |= TSF_XFERABLE;
                if (tdq->tdq_transferable >= busy_thresh &&
                    (tdq->tdq_flags & TDQF_BUSY) == 0) {
                        tdq->tdq_flags |= TDQF_BUSY;
                        atomic_set_int(&tdq_busy, 1 << TDQ_ID(tdq));
                }
        }
#endif
        if (ts->ts_runq == &tdq->tdq_timeshare) {
                u_char pri;

                pri = ts->ts_thread->td_priority;
                KASSERT(pri <= PRI_MAX_TIMESHARE && pri >= PRI_MIN_TIMESHARE,
                        ("Invalid priority %d on timeshare runq", pri));
                /*
                 * This queue contains only priorities between MIN and MAX
                 * realtime.  Use the whole queue to represent these values.
                 */
#define TS_RQ_PPQ       (((PRI_MAX_TIMESHARE - PRI_MIN_TIMESHARE) + 1) / RQ_NQS)
                if ((flags & SRQ_BORROWING) == 0) {
                        pri = (pri - PRI_MIN_TIMESHARE) / TS_RQ_PPQ;
                        pri = (pri + tdq->tdq_idx) % RQ_NQS;
                        /*
                         * This effectively shortens the queue by one so we
                         * can have a one slot difference between idx and
                         * ridx while we wait for threads to drain.
                         */
                        if (tdq->tdq_ridx != tdq->tdq_idx &&
                            pri == tdq->tdq_ridx)
                                pri = (pri - 1) % RQ_NQS;
                } else
                        pri = tdq->tdq_ridx;
                runq_add_pri(ts->ts_runq, ts, pri, flags);
        } else
                runq_add(ts->ts_runq, ts, flags);
}

static __inline void
tdq_runq_rem(struct tdq *tdq, struct td_sched *ts)
{
#ifdef SMP
        if (ts->ts_flags & TSF_XFERABLE) {
                tdq->tdq_transferable--;
                tdq->tdq_group->tdg_transferable--;
                ts->ts_flags &= ~TSF_XFERABLE;
                if (tdq->tdq_transferable < busy_thresh && 
                    (tdq->tdq_flags & TDQF_BUSY)) {
                        atomic_clear_int(&tdq_busy, 1 << TDQ_ID(tdq));
                        tdq->tdq_flags &= ~TDQF_BUSY;
                }
        }
#endif
        if (ts->ts_runq == &tdq->tdq_timeshare) {
                if (tdq->tdq_idx != tdq->tdq_ridx)
                        runq_remove_idx(ts->ts_runq, ts, &tdq->tdq_ridx);
                else
                        runq_remove_idx(ts->ts_runq, ts, NULL);
                /*
                 * For timeshare threads we update the priority here so
                 * the priority reflects the time we've been sleeping.
                 */
                ts->ts_ltick = ticks;
                sched_pctcpu_update(ts);
                sched_priority(ts->ts_thread);
        } else
                runq_remove(ts->ts_runq, ts);
}

static void
tdq_load_add(struct tdq *tdq, struct td_sched *ts)
{
        int class;
        mtx_assert(&sched_lock, MA_OWNED);
        class = PRI_BASE(ts->ts_thread->td_pri_class);
        tdq->tdq_load++;
        CTR1(KTR_SCHED, "load: %d", tdq->tdq_load);
        if (class != PRI_ITHD &&
            (ts->ts_thread->td_proc->p_flag & P_NOLOAD) == 0)
#ifdef SMP
                tdq->tdq_group->tdg_load++;
#else
                tdq->tdq_sysload++;
#endif
}

static void
tdq_load_rem(struct tdq *tdq, struct td_sched *ts)
{
        int class;
        mtx_assert(&sched_lock, MA_OWNED);
        class = PRI_BASE(ts->ts_thread->td_pri_class);
        if (class != PRI_ITHD &&
            (ts->ts_thread->td_proc->p_flag & P_NOLOAD) == 0)
#ifdef SMP
                tdq->tdq_group->tdg_load--;
#else
                tdq->tdq_sysload--;
#endif
        tdq->tdq_load--;
        CTR1(KTR_SCHED, "load: %d", tdq->tdq_load);
        ts->ts_runq = NULL;
}

#ifdef SMP
static void
sched_smp_tick(struct thread *td)
{
        struct tdq *tdq;

        tdq = TDQ_SELF();
        if (rebalance) {
                if (ticks >= bal_tick)
                        sched_balance();
                if (ticks >= gbal_tick && balance_groups)
                        sched_balance_groups();
        }
        td->td_sched->ts_rltick = ticks;
}

/*
 * sched_balance is a simple CPU load balancing algorithm.  It operates by
 * finding the least loaded and most loaded cpu and equalizing their load
 * by migrating some processes.
 *
 * Dealing only with two CPUs at a time has two advantages.  Firstly, most
 * installations will only have 2 cpus.  Secondly, load balancing too much at
 * once can have an unpleasant effect on the system.  The scheduler rarely has
 * enough information to make perfect decisions.  So this algorithm chooses
 * algorithm simplicity and more gradual effects on load in larger systems.
 *
 * It could be improved by considering the priorities and slices assigned to
 * each task prior to balancing them.  There are many pathological cases with
 * any approach and so the semi random algorithm below may work as well as any.
 *
 */
static void
sched_balance(void)
{
        struct tdq_group *high;
        struct tdq_group *low;
        struct tdq_group *tdg;
        int cnt;
        int i;

        bal_tick = ticks + (random() % (hz * 2));
        if (smp_started == 0)
                return;
        low = high = NULL;
        i = random() % (tdg_maxid + 1);
        for (cnt = 0; cnt <= tdg_maxid; cnt++) {
                tdg = TDQ_GROUP(i);
                /*
                 * Find the CPU with the highest load that has some
                 * threads to transfer.
                 */
                if ((high == NULL || tdg->tdg_load > high->tdg_load)
                    && tdg->tdg_transferable)
                        high = tdg;
                if (low == NULL || tdg->tdg_load < low->tdg_load)
                        low = tdg;
                if (++i > tdg_maxid)
                        i = 0;
        }
        if (low != NULL && high != NULL && high != low)
                sched_balance_pair(LIST_FIRST(&high->tdg_members),
                    LIST_FIRST(&low->tdg_members));
}

static void
sched_balance_groups(void)
{
        int i;

        gbal_tick = ticks + (random() % (hz * 2));
        mtx_assert(&sched_lock, MA_OWNED);
        if (smp_started)
                for (i = 0; i <= tdg_maxid; i++)
                        sched_balance_group(TDQ_GROUP(i));
}

static void
sched_balance_group(struct tdq_group *tdg)
{
        struct tdq *tdq;
        struct tdq *high;
        struct tdq *low;
        int load;

        if (tdg->tdg_transferable == 0)
                return;
        low = NULL;
        high = NULL;
        LIST_FOREACH(tdq, &tdg->tdg_members, tdq_siblings) {
                load = tdq->tdq_load;
                if (high == NULL || load > high->tdq_load)
                        high = tdq;
                if (low == NULL || load < low->tdq_load)
                        low = tdq;
        }
        if (high != NULL && low != NULL && high != low)
                sched_balance_pair(high, low);
}

static void
sched_balance_pair(struct tdq *high, struct tdq *low)
{
        int transferable;
        int high_load;
        int low_load;
        int move;
        int diff;
        int i;

        /*
         * If we're transfering within a group we have to use this specific
         * tdq's transferable count, otherwise we can steal from other members
         * of the group.
         */
        if (high->tdq_group == low->tdq_group) {
                transferable = high->tdq_transferable;
                high_load = high->tdq_load;
                low_load = low->tdq_load;
        } else {
                transferable = high->tdq_group->tdg_transferable;
                high_load = high->tdq_group->tdg_load;
                low_load = low->tdq_group->tdg_load;
        }
        if (transferable == 0)
                return;
        /*
         * Determine what the imbalance is and then adjust that to how many
         * threads we actually have to give up (transferable).
         */
        diff = high_load - low_load;
        move = diff / 2;
        if (diff & 0x1)
                move++;
        move = min(move, transferable);
        for (i = 0; i < move; i++)
                tdq_move(high, TDQ_ID(low));
        return;
}

static void
tdq_move(struct tdq *from, int cpu)
{
        struct tdq *tdq;
        struct tdq *to;
        struct td_sched *ts;

        tdq = from;
        to = TDQ_CPU(cpu);
        ts = tdq_steal(tdq, 1);
        if (ts == NULL) {
                struct tdq_group *tdg;

                tdg = tdq->tdq_group;
                LIST_FOREACH(tdq, &tdg->tdg_members, tdq_siblings) {
                        if (tdq == from || tdq->tdq_transferable == 0)
                                continue;
                        ts = tdq_steal(tdq, 1);
                        break;
                }
                if (ts == NULL)
                        panic("tdq_move: No threads available with a "
                            "transferable count of %d\n", 
                            tdg->tdg_transferable);
        }
        if (tdq == to)
                return;
        sched_rem(ts->ts_thread);
        ts->ts_cpu = cpu;
        sched_pin_td(ts->ts_thread);
        sched_add(ts->ts_thread, SRQ_YIELDING);
        sched_unpin_td(ts->ts_thread);
}

static int
tdq_idled(struct tdq *tdq)
{
        struct tdq_group *tdg;
        struct tdq *steal;
        struct td_sched *ts;

        tdg = tdq->tdq_group;
        /*
         * If we're in a cpu group, try and steal threads from another cpu in
         * the group before idling.
         */
        if (steal_htt && tdg->tdg_cpus > 1 && tdg->tdg_transferable) {
                LIST_FOREACH(steal, &tdg->tdg_members, tdq_siblings) {
                        if (steal == tdq || steal->tdq_transferable == 0)
                                continue;
                        ts = tdq_steal(steal, 0);
                        if (ts)
                                goto steal;
                }
        }
        if (steal_busy) {
                while (tdq_busy) {
                        int cpu;

                        cpu = ffs(tdq_busy);
                        if (cpu == 0)
                                break;
                        cpu--;
                        steal = TDQ_CPU(cpu);
                        if (steal->tdq_transferable == 0)
                                continue;
                        ts = tdq_steal(steal, 1);
                        if (ts == NULL)
                                continue;
                        CTR5(KTR_ULE,
                            "tdq_idled: stealing td %p(%s) pri %d from %d busy 0x%X",
                            ts->ts_thread, ts->ts_thread->td_proc->p_comm,
                            ts->ts_thread->td_priority, cpu, tdq_busy);
                        goto steal;
                }
        }
        /*
         * We only set the idled bit when all of the cpus in the group are
         * idle.  Otherwise we could get into a situation where a thread bounces
         * back and forth between two idle cores on seperate physical CPUs.
         */
        tdg->tdg_idlemask |= PCPU_GET(cpumask);
        if (tdg->tdg_idlemask == tdg->tdg_cpumask)
                atomic_set_int(&tdq_idle, tdg->tdg_mask);
        return (1);
steal:
        sched_rem(ts->ts_thread);
        ts->ts_cpu = PCPU_GET(cpuid);
        sched_pin_td(ts->ts_thread);
        sched_add(ts->ts_thread, SRQ_YIELDING);
        sched_unpin_td(ts->ts_thread);

        return (0);
}

static void
tdq_notify(struct td_sched *ts)
{
        struct thread *ctd;
        struct pcpu *pcpu;
        int cpri;
        int pri;
        int cpu;

        cpu = ts->ts_cpu;
        pri = ts->ts_thread->td_priority;
        pcpu = pcpu_find(cpu);
        ctd = pcpu->pc_curthread;
        cpri = ctd->td_priority;

        /*
         * If our priority is not better than the current priority there is
         * nothing to do.
         */
        if (pri > cpri)
                return;
        /*
         * Always IPI idle.
         */
        if (cpri > PRI_MIN_IDLE)
                goto sendipi;
        /*
         * If we're realtime or better and there is timeshare or worse running
         * send an IPI.
         */
        if (pri < PRI_MAX_REALTIME && cpri > PRI_MAX_REALTIME)
                goto sendipi;
        /*
         * Otherwise only IPI if we exceed the threshold.
         */
        if (pri > ipi_thresh)
                return;
sendipi:
        ctd->td_flags |= TDF_NEEDRESCHED;
        if (cpri < PRI_MIN_IDLE) {
                if (ipi_ast)
                        ipi_selected(1 << cpu, IPI_AST);
                else if (ipi_preempt)
                        ipi_selected(1 << cpu, IPI_PREEMPT);
        } else 
                ipi_selected(1 << cpu, IPI_PREEMPT);
}

static struct td_sched *
runq_steal(struct runq *rq)
{
        struct rqhead *rqh;
        struct rqbits *rqb;
        struct td_sched *ts;
        int word;
        int bit;

        mtx_assert(&sched_lock, MA_OWNED);
        rqb = &rq->rq_status;
        for (word = 0; word < RQB_LEN; word++) {
                if (rqb->rqb_bits[word] == 0)
                        continue;
                for (bit = 0; bit < RQB_BPW; bit++) {
                        if ((rqb->rqb_bits[word] & (1ul << bit)) == 0)
                                continue;
                        rqh = &rq->rq_queues[bit + (word << RQB_L2BPW)];
                        TAILQ_FOREACH(ts, rqh, ts_procq) {
                                if (THREAD_CAN_MIGRATE(ts->ts_thread))
                                        return (ts);
                        }
                }
        }
        return (NULL);
}

static struct td_sched *
tdq_steal(struct tdq *tdq, int stealidle)
{
        struct td_sched *ts;

        /*
         * Steal from next first to try to get a non-interactive task that
         * may not have run for a while.
         * XXX Need to effect steal order for timeshare threads.
         */
        if ((ts = runq_steal(&tdq->tdq_realtime)) != NULL)
                return (ts);
        if ((ts = runq_steal(&tdq->tdq_timeshare)) != NULL)
                return (ts);
        if (stealidle)
                return (runq_steal(&tdq->tdq_idle));
        return (NULL);
}

int
tdq_pickidle(struct tdq *tdq, struct td_sched *ts)
{
        struct tdq_group *tdg;
        int self;
        int cpu;

        self = PCPU_GET(cpuid);
        if (smp_started == 0)
                return (self);
        /*
         * If the current CPU has idled, just run it here.
         */
        if ((tdq->tdq_group->tdg_idlemask & PCPU_GET(cpumask)) != 0)
                return (self);
        /*
         * Try the last group we ran on.
         */
        tdg = TDQ_CPU(ts->ts_cpu)->tdq_group;
        cpu = ffs(tdg->tdg_idlemask);
        if (cpu)
                return (cpu - 1);
        /*
         * Search for an idle group.
         */
        cpu = ffs(tdq_idle);
        if (cpu) 
                return (cpu - 1);
        /*
         * XXX If there are no idle groups, check for an idle core.
         */
        /*
         * No idle CPUs?
         */
        return (self);
}

static int
tdq_pickpri(struct tdq *tdq, struct td_sched *ts, int flags)
{
        struct pcpu *pcpu;
        int lowpri;
        int lowcpu;
        int lowload;
        int load;
        int self;
        int pri;
        int cpu;

        self = PCPU_GET(cpuid);
        if (smp_started == 0)
                return (self);

        pri = ts->ts_thread->td_priority;
        /*
         * Regardless of affinity, if the last cpu is idle send it there.
         */
        pcpu = pcpu_find(ts->ts_cpu);
        if (pcpu->pc_curthread->td_priority > PRI_MIN_IDLE) {
                CTR5(KTR_ULE,
                    "ts_cpu %d idle, ltick %d ticks %d pri %d curthread %d",
                    ts->ts_cpu, ts->ts_rltick, ticks, pri,
                    pcpu->pc_curthread->td_priority);
                return (ts->ts_cpu);
        }
        /*
         * If we have affinity, try to place it on the cpu we last ran on.
         */
        if (SCHED_AFFINITY(ts) && pcpu->pc_curthread->td_priority > pri) {
                CTR5(KTR_ULE,
                    "affinity for %d, ltick %d ticks %d pri %d curthread %d",
                    ts->ts_cpu, ts->ts_rltick, ticks, pri,
                    pcpu->pc_curthread->td_priority);
                return (ts->ts_cpu);
        }
        /*
         * Try ourself first; If we're running something lower priority this
         * may have some locality with the waking thread and execute faster
         * here.
         */
        if (tryself) {
                /*
                 * If we're being awoken by an interrupt thread or the waker
                 * is going right to sleep run here as well.
                 */
                if ((TDQ_SELF()->tdq_load == 1) && (flags & SRQ_YIELDING ||
                    curthread->td_pri_class == PRI_ITHD)) {
                        CTR2(KTR_ULE, "tryself load %d flags %d",
                            TDQ_SELF()->tdq_load, flags);
                        return (self);
                }
        }
        /*
         * Look for an idle group.
         */
        CTR1(KTR_ULE, "tdq_idle %X", tdq_idle);
        cpu = ffs(tdq_idle);
        if (cpu)
                return (cpu - 1);
        if (tryselfidle && pri < curthread->td_priority) {
                CTR1(KTR_ULE, "tryself %d",
                    curthread->td_priority);
                return (self);
        }
        /*
         * Now search for the cpu running the lowest priority thread with
         * the least load.
         */
        lowload = 0;
        lowpri = lowcpu = 0;
        for (cpu = 0; cpu <= mp_maxid; cpu++) {
                if (CPU_ABSENT(cpu))
                        continue;
                pcpu = pcpu_find(cpu);
                pri = pcpu->pc_curthread->td_priority;
                CTR4(KTR_ULE,
                    "cpu %d pri %d lowcpu %d lowpri %d",
                    cpu, pri, lowcpu, lowpri);
                if (pri < lowpri)
                        continue;
                load = TDQ_CPU(cpu)->tdq_load;
                if (lowpri && lowpri == pri && load > lowload)
                        continue;
                lowpri = pri;
                lowcpu = cpu;
                lowload = load;
        }

        return (lowcpu);
}

#endif  /* SMP */

/*
 * Pick the highest priority task we have and return it.
 */

static struct td_sched *
tdq_choose(struct tdq *tdq)
{
        struct td_sched *ts;

        mtx_assert(&sched_lock, MA_OWNED);

        ts = runq_choose(&tdq->tdq_realtime);
        if (ts != NULL) {
                KASSERT(ts->ts_thread->td_priority <= PRI_MAX_REALTIME,
                    ("tdq_choose: Invalid priority on realtime queue %d",
                    ts->ts_thread->td_priority));
                return (ts);
        }
        ts = runq_choose_from(&tdq->tdq_timeshare, tdq->tdq_ridx);
        if (ts != NULL) {
                KASSERT(ts->ts_thread->td_priority <= PRI_MAX_TIMESHARE &&
                    ts->ts_thread->td_priority >= PRI_MIN_TIMESHARE,
                    ("tdq_choose: Invalid priority on timeshare queue %d",
                    ts->ts_thread->td_priority));
                return (ts);
        }

        ts = runq_choose(&tdq->tdq_idle);
        if (ts != NULL) {
                KASSERT(ts->ts_thread->td_priority >= PRI_MIN_IDLE,
                    ("tdq_choose: Invalid priority on idle queue %d",
                    ts->ts_thread->td_priority));
                return (ts);
        }

        return (NULL);
}

static void
tdq_setup(struct tdq *tdq)
{
        runq_init(&tdq->tdq_realtime);
        runq_init(&tdq->tdq_timeshare);
        runq_init(&tdq->tdq_idle);
        tdq->tdq_load = 0;
}

static void
sched_setup(void *dummy)
{
#ifdef SMP
        int i;
#endif

        /*
         * To avoid divide-by-zero, we set realstathz a dummy value
         * in case which sched_clock() called before sched_initticks().
         */
        realstathz = hz;
        sched_slice = (realstathz/10);  /* ~100ms */
        tickincr = 1 << SCHED_TICK_SHIFT;

#ifdef SMP
        balance_groups = 0;
        /*
         * Initialize the tdqs.
         */
        for (i = 0; i < MAXCPU; i++) {
                struct tdq *tdq;

                tdq = &tdq_cpu[i];
                tdq_setup(&tdq_cpu[i]);
        }
        if (smp_topology == NULL) {
                struct tdq_group *tdg;
                struct tdq *tdq;
                int cpus;

                for (cpus = 0, i = 0; i < MAXCPU; i++) {
                        if (CPU_ABSENT(i))
                                continue;
                        tdq = &tdq_cpu[i];
                        tdg = &tdq_groups[cpus];
                        /*
                         * Setup a tdq group with one member.
                         */
                        tdq->tdq_transferable = 0;
                        tdq->tdq_group = tdg;
                        tdg->tdg_cpus = 1;
                        tdg->tdg_idlemask = 0;
                        tdg->tdg_cpumask = tdg->tdg_mask = 1 << i;
                        tdg->tdg_load = 0;
                        tdg->tdg_transferable = 0;
                        LIST_INIT(&tdg->tdg_members);
                        LIST_INSERT_HEAD(&tdg->tdg_members, tdq, tdq_siblings);
                        cpus++;
                }
                tdg_maxid = cpus - 1;
        } else {
                struct tdq_group *tdg;
                struct cpu_group *cg;
                int j;

                for (i = 0; i < smp_topology->ct_count; i++) {
                        cg = &smp_topology->ct_group[i];
                        tdg = &tdq_groups[i];
                        /*
                         * Initialize the group.
                         */
                        tdg->tdg_idlemask = 0;
                        tdg->tdg_load = 0;
                        tdg->tdg_transferable = 0;
                        tdg->tdg_cpus = cg->cg_count;
                        tdg->tdg_cpumask = cg->cg_mask;
                        LIST_INIT(&tdg->tdg_members);
                        /*
                         * Find all of the group members and add them.
                         */
                        for (j = 0; j < MAXCPU; j++) {
                                if ((cg->cg_mask & (1 << j)) != 0) {
                                        if (tdg->tdg_mask == 0)
                                                tdg->tdg_mask = 1 << j;
                                        tdq_cpu[j].tdq_transferable = 0;
                                        tdq_cpu[j].tdq_group = tdg;
                                        LIST_INSERT_HEAD(&tdg->tdg_members,
                                            &tdq_cpu[j], tdq_siblings);
                                }
                        }
                        if (tdg->tdg_cpus > 1)
                                balance_groups = 1;
                }
                tdg_maxid = smp_topology->ct_count - 1;
        }
        /*
         * Stagger the group and global load balancer so they do not
         * interfere with each other.
         */
        bal_tick = ticks + hz;
        if (balance_groups)
                gbal_tick = ticks + (hz / 2);
#else
        tdq_setup(TDQ_SELF());
#endif
        mtx_lock_spin(&sched_lock);
        tdq_load_add(TDQ_SELF(), &td_sched0);
        mtx_unlock_spin(&sched_lock);
}

/* ARGSUSED */
static void
sched_initticks(void *dummy)
{
        mtx_lock_spin(&sched_lock);
        realstathz = stathz ? stathz : hz;
        sched_slice = (realstathz/10);  /* ~100ms */

        /*
         * tickincr is shifted out by 10 to avoid rounding errors due to
         * hz not being evenly divisible by stathz on all platforms.
         */
        tickincr = (hz << SCHED_TICK_SHIFT) / realstathz;
        /*
         * This does not work for values of stathz that are more than
         * 1 << SCHED_TICK_SHIFT * hz.  In practice this does not happen.
         */
        if (tickincr == 0)
                tickincr = 1;
#ifdef SMP
        affinity = SCHED_AFFINITY_DEFAULT;
#endif
        mtx_unlock_spin(&sched_lock);
}


/*
 * Scale the scheduling priority according to the "interactivity" of this
 * process.
 */
static void
sched_priority(struct thread *td)
{
        int score;
        int pri;

        if (td->td_pri_class != PRI_TIMESHARE)
                return;
        /*
         * If the score is interactive we place the thread in the realtime
         * queue with a priority that is less than kernel and interrupt
         * priorities.  These threads are not subject to nice restrictions.
         *
         * Scores greater than this are placed on the normal realtime queue
         * where the priority is partially decided by the most recent cpu
         * utilization and the rest is decided by nice value.
         */
        score = sched_interact_score(td);
        if (score < sched_interact) {
                pri = PRI_MIN_REALTIME;
                pri += ((PRI_MAX_REALTIME - PRI_MIN_REALTIME) / sched_interact)
                    * score;
                KASSERT(pri >= PRI_MIN_REALTIME && pri <= PRI_MAX_REALTIME,
                    ("sched_priority: invalid interactive priority %d score %d",
                    pri, score));
        } else {
                pri = SCHED_PRI_MIN;
                if (td->td_sched->ts_ticks)
                        pri += SCHED_PRI_TICKS(td->td_sched);
                pri += SCHED_PRI_NICE(td->td_proc->p_nice);
                if (!(pri >= PRI_MIN_TIMESHARE && pri <= PRI_MAX_TIMESHARE)) {
                        static int once = 1;
                        if (once) {
                                printf("sched_priority: invalid priority %d",
                                    pri);
                                printf("nice %d, ticks %d ftick %d ltick %d tick pri %d\n",
                                    td->td_proc->p_nice,
                                    td->td_sched->ts_ticks,
                                    td->td_sched->ts_ftick,
                                    td->td_sched->ts_ltick,
                                    SCHED_PRI_TICKS(td->td_sched));
                                once = 0;
                        }
                        pri = min(max(pri, PRI_MIN_TIMESHARE),
                            PRI_MAX_TIMESHARE);
                }
        }
        sched_user_prio(td, pri);

        return;
}

/*
 * This routine enforces a maximum limit on the amount of scheduling history
 * kept.  It is called after either the slptime or runtime is adjusted.
 */
static void
sched_interact_update(struct thread *td)
{
        struct td_sched *ts;
        u_int sum;

        ts = td->td_sched;
        sum = ts->skg_runtime + ts->skg_slptime;
        if (sum < SCHED_SLP_RUN_MAX)
                return;
        /*
         * This only happens from two places:
         * 1) We have added an unusual amount of run time from fork_exit.
         * 2) We have added an unusual amount of sleep time from sched_sleep().
         */
        if (sum > SCHED_SLP_RUN_MAX * 2) {
                if (ts->skg_runtime > ts->skg_slptime) {
                        ts->skg_runtime = SCHED_SLP_RUN_MAX;
                        ts->skg_slptime = 1;
                } else {
                        ts->skg_slptime = SCHED_SLP_RUN_MAX;
                        ts->skg_runtime = 1;
                }
                return;
        }
        /*
         * If we have exceeded by more than 1/5th then the algorithm below
         * will not bring us back into range.  Dividing by two here forces
         * us into the range of [4/5 * SCHED_INTERACT_MAX, SCHED_INTERACT_MAX]
         */
        if (sum > (SCHED_SLP_RUN_MAX / 5) * 6) {
                ts->skg_runtime /= 2;
                ts->skg_slptime /= 2;
                return;
        }
        ts->skg_runtime = (ts->skg_runtime / 5) * 4;
        ts->skg_slptime = (ts->skg_slptime / 5) * 4;
}

static void
sched_interact_fork(struct thread *td)
{
        int ratio;
        int sum;

        sum = td->td_sched->skg_runtime + td->td_sched->skg_slptime;
        if (sum > SCHED_SLP_RUN_FORK) {
                ratio = sum / SCHED_SLP_RUN_FORK;
                td->td_sched->skg_runtime /= ratio;
                td->td_sched->skg_slptime /= ratio;
        }
}

static int
sched_interact_score(struct thread *td)
{
        int div;

        if (td->td_sched->skg_runtime > td->td_sched->skg_slptime) {
                div = max(1, td->td_sched->skg_runtime / SCHED_INTERACT_HALF);
                return (SCHED_INTERACT_HALF +
                    (SCHED_INTERACT_HALF - (td->td_sched->skg_slptime / div)));
        } if (td->td_sched->skg_slptime > td->td_sched->skg_runtime) {
                div = max(1, td->td_sched->skg_slptime / SCHED_INTERACT_HALF);
                return (td->td_sched->skg_runtime / div);
        }

        /*
         * This can happen if slptime and runtime are 0.
         */
        return (0);

}

/*
 * Called from proc0_init() to bootstrap the scheduler.
 */
void
schedinit(void)
{

        /*
         * Set up the scheduler specific parts of proc0.
         */
        proc0.p_sched = NULL; /* XXX */
        thread0.td_sched = &td_sched0;
        td_sched0.ts_ltick = ticks;
        td_sched0.ts_ftick = ticks;
        td_sched0.ts_thread = &thread0;
}

/*
 * This is only somewhat accurate since given many processes of the same
 * priority they will switch when their slices run out, which will be
 * at most sched_slice stathz ticks.
 */
int
sched_rr_interval(void)
{

        /* Convert sched_slice to hz */
        return (hz/(realstathz/sched_slice));
}

static void
sched_pctcpu_update(struct td_sched *ts)
{

        if (ts->ts_ticks == 0)
                return;
        if (ticks - (hz / 10) < ts->ts_ltick &&
            SCHED_TICK_TOTAL(ts) < SCHED_TICK_MAX)
                return;
        /*
         * Adjust counters and watermark for pctcpu calc.
         */
        if (ts->ts_ltick > ticks - SCHED_TICK_TARG)
                ts->ts_ticks = (ts->ts_ticks / (ticks - ts->ts_ftick)) *
                            SCHED_TICK_TARG;
        else
                ts->ts_ticks = 0;
        ts->ts_ltick = ticks;
        ts->ts_ftick = ts->ts_ltick - SCHED_TICK_TARG;
}

static void
sched_thread_priority(struct thread *td, u_char prio)
{
        struct td_sched *ts;

        CTR6(KTR_SCHED, "sched_prio: %p(%s) prio %d newprio %d by %p(%s)",
            td, td->td_proc->p_comm, td->td_priority, prio, curthread,
            curthread->td_proc->p_comm);
        ts = td->td_sched;
        mtx_assert(&sched_lock, MA_OWNED);
        if (td->td_priority == prio)
                return;

        if (TD_ON_RUNQ(td) && prio < td->td_priority) {
                /*
                 * If the priority has been elevated due to priority
                 * propagation, we may have to move ourselves to a new
                 * queue.  This could be optimized to not re-add in some
                 * cases.
                 */
                sched_rem(td);
                td->td_priority = prio;
                sched_add(td, SRQ_BORROWING);
        } else
                td->td_priority = prio;
}

/*
 * Update a thread's priority when it is lent another thread's
 * priority.
 */
void
sched_lend_prio(struct thread *td, u_char prio)
{

        td->td_flags |= TDF_BORROWING;
        sched_thread_priority(td, prio);
}

/*
 * Restore a thread's priority when priority propagation is
 * over.  The prio argument is the minimum priority the thread
 * needs to have to satisfy other possible priority lending
 * requests.  If the thread's regular priority is less
 * important than prio, the thread will keep a priority boost
 * of prio.
 */
void
sched_unlend_prio(struct thread *td, u_char prio)
{
        u_char base_pri;

        if (td->td_base_pri >= PRI_MIN_TIMESHARE &&
            td->td_base_pri <= PRI_MAX_TIMESHARE)
                base_pri = td->td_user_pri;
        else
                base_pri = td->td_base_pri;
        if (prio >= base_pri) {
                td->td_flags &= ~TDF_BORROWING;
                sched_thread_priority(td, base_pri);
        } else
                sched_lend_prio(td, prio);
}

void
sched_prio(struct thread *td, u_char prio)
{
        u_char oldprio;

        /* First, update the base priority. */
        td->td_base_pri = prio;

        /*
         * If the thread is borrowing another thread's priority, don't
         * ever lower the priority.
         */
        if (td->td_flags & TDF_BORROWING && td->td_priority < prio)
                return;

        /* Change the real priority. */
        oldprio = td->td_priority;
        sched_thread_priority(td, prio);

        /*
         * If the thread is on a turnstile, then let the turnstile update
         * its state.
         */
        if (TD_ON_LOCK(td) && oldprio != prio)
                turnstile_adjust(td, oldprio);
}

void
sched_user_prio(struct thread *td, u_char prio)
{
        u_char oldprio;

        td->td_base_user_pri = prio;
        if (td->td_flags & TDF_UBORROWING && td->td_user_pri <= prio)
                return;
        oldprio = td->td_user_pri;
        td->td_user_pri = prio;

        if (TD_ON_UPILOCK(td) && oldprio != prio)
                umtx_pi_adjust(td, oldprio);
}

void
sched_lend_user_prio(struct thread *td, u_char prio)
{
        u_char oldprio;

        td->td_flags |= TDF_UBORROWING;

        oldprio = td->td_user_pri;
        td->td_user_pri = prio;

        if (TD_ON_UPILOCK(td) && oldprio != prio)
                umtx_pi_adjust(td, oldprio);
}

void
sched_unlend_user_prio(struct thread *td, u_char prio)
{
        u_char base_pri;

        base_pri = td->td_base_user_pri;
        if (prio >= base_pri) {
                td->td_flags &= ~TDF_UBORROWING;
                sched_user_prio(td, base_pri);
        } else
                sched_lend_user_prio(td, prio);
}

void
sched_switch(struct thread *td, struct thread *newtd, int flags)
{
        struct tdq *tdq;
        struct td_sched *ts;
        int preempt;

        mtx_assert(&sched_lock, MA_OWNED);

        preempt = flags & SW_PREEMPT;
        tdq = TDQ_SELF();
        ts = td->td_sched;
        td->td_lastcpu = td->td_oncpu;
        td->td_oncpu = NOCPU;
        td->td_flags &= ~TDF_NEEDRESCHED;
        td->td_owepreempt = 0;
        /*
         * If the thread has been assigned it may be in the process of switching
         * to the new cpu.  This is the case in sched_bind().
         */
        if (td == PCPU_GET(idlethread)) {
                TD_SET_CAN_RUN(td);
        } else {
                tdq_load_rem(tdq, ts);
                if (TD_IS_RUNNING(td)) {
                        /*
                         * Don't allow the thread to migrate
                         * from a preemption.
                         */
                        if (preempt)
                                sched_pin_td(td);
                        sched_add(td, preempt ?
                            SRQ_OURSELF|SRQ_YIELDING|SRQ_PREEMPTED :
                            SRQ_OURSELF|SRQ_YIELDING);
                        if (preempt)
                                sched_unpin_td(td);
                }
        }
        if (newtd != NULL) {
                /*
                 * If we bring in a thread account for it as if it had been
                 * added to the run queue and then chosen.
                 */
                TD_SET_RUNNING(newtd);
                tdq_load_add(TDQ_SELF(), newtd->td_sched);
        } else
                newtd = choosethread();
        if (td != newtd) {
#ifdef  HWPMC_HOOKS
                if (PMC_PROC_IS_USING_PMCS(td->td_proc))
                        PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT);
#endif

                cpu_switch(td, newtd);
#ifdef  HWPMC_HOOKS
                if (PMC_PROC_IS_USING_PMCS(td->td_proc))
                        PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_IN);
#endif
        }
        sched_lock.mtx_lock = (uintptr_t)td;
        td->td_oncpu = PCPU_GET(cpuid);
}

void
sched_nice(struct proc *p, int nice)
{
        struct thread *td;

        PROC_LOCK_ASSERT(p, MA_OWNED);
        mtx_assert(&sched_lock, MA_OWNED);

        p->p_nice = nice;
        FOREACH_THREAD_IN_PROC(p, td) {
                sched_priority(td);
                sched_prio(td, td->td_base_user_pri);
        }
}

void
sched_sleep(struct thread *td)
{

        mtx_assert(&sched_lock, MA_OWNED);

        td->td_sched->ts_slptime = ticks;
}

void
sched_wakeup(struct thread *td)
{
        struct td_sched *ts;
        int slptime;

        mtx_assert(&sched_lock, MA_OWNED);
        ts = td->td_sched;
        /*
         * If we slept for more than a tick update our interactivity and
         * priority.
         */
        slptime = ts->ts_slptime;
        ts->ts_slptime = 0;
        if (slptime && slptime != ticks) {
                u_int hzticks;

                hzticks = (ticks - slptime) << SCHED_TICK_SHIFT;
                ts->skg_slptime += hzticks;
                sched_interact_update(td);
                sched_pctcpu_update(ts);
                sched_priority(td);
        }
        /* Reset the slice value after we sleep. */
        ts->ts_slice = sched_slice;
        sched_add(td, SRQ_BORING);
}

/*
 * Penalize the parent for creating a new child and initialize the child's
 * priority.
 */
void
sched_fork(struct thread *td, struct thread *child)
{
        mtx_assert(&sched_lock, MA_OWNED);
        sched_fork_thread(td, child);
        /*
         * Penalize the parent and child for forking.
         */
        sched_interact_fork(child);
        sched_priority(child);
        td->td_sched->skg_runtime += tickincr;
        sched_interact_update(td);
        sched_priority(td);
}

void
sched_fork_thread(struct thread *td, struct thread *child)
{
        struct td_sched *ts;
        struct td_sched *ts2;

        /*
         * Initialize child.
         */
        sched_newthread(child);
        ts = td->td_sched;
        ts2 = child->td_sched;
        ts2->ts_cpu = ts->ts_cpu;
        ts2->ts_runq = NULL;
        /*
         * Grab our parents cpu estimation information and priority.
         */
        ts2->ts_ticks = ts->ts_ticks;
        ts2->ts_ltick = ts->ts_ltick;
        ts2->ts_ftick = ts->ts_ftick;
        child->td_user_pri = td->td_user_pri;
        child->td_base_user_pri = td->td_base_user_pri;
        /*
         * And update interactivity score.
         */
        ts2->skg_slptime = ts->skg_slptime;
        ts2->skg_runtime = ts->skg_runtime;
        ts2->ts_slice = 1;      /* Attempt to quickly learn interactivity. */
}

void
sched_class(struct thread *td, int class)
{

        mtx_assert(&sched_lock, MA_OWNED);
        if (td->td_pri_class == class)
                return;

#ifdef SMP
        /*
         * On SMP if we're on the RUNQ we must adjust the transferable
         * count because could be changing to or from an interrupt
         * class.
         */
        if (TD_ON_RUNQ(td)) {
                struct tdq *tdq;

                tdq = TDQ_CPU(td->td_sched->ts_cpu);
                if (THREAD_CAN_MIGRATE(td)) {
                        tdq->tdq_transferable--;
                        tdq->tdq_group->tdg_transferable--;
                }
                td->td_pri_class = class;
                if (THREAD_CAN_MIGRATE(td)) {
                        tdq->tdq_transferable++;
                        tdq->tdq_group->tdg_transferable++;
                }
        }
#endif
        td->td_pri_class = class;
}

/*
 * Return some of the child's priority and interactivity to the parent.
 */
void
sched_exit(struct proc *p, struct thread *child)
{
        struct thread *td;
        
        CTR3(KTR_SCHED, "sched_exit: %p(%s) prio %d",
            child, child->td_proc->p_comm, child->td_priority);

        td = FIRST_THREAD_IN_PROC(p);
        sched_exit_thread(td, child);
}

void
sched_exit_thread(struct thread *td, struct thread *child)
{

        CTR3(KTR_SCHED, "sched_exit_thread: %p(%s) prio %d",
            child, child->td_proc->p_comm, child->td_priority);

        tdq_load_rem(TDQ_CPU(child->td_sched->ts_cpu), child->td_sched);
#ifdef KSE
        /*
         * KSE forks and exits so often that this penalty causes short-lived
         * threads to always be non-interactive.  This causes mozilla to
         * crawl under load.
         */
        if ((td->td_pflags & TDP_SA) && td->td_proc == child->td_proc)
                return;
#endif
        /*
         * Give the child's runtime to the parent without returning the
         * sleep time as a penalty to the parent.  This causes shells that
         * launch expensive things to mark their children as expensive.
         */
        td->td_sched->skg_runtime += child->td_sched->skg_runtime;
        sched_interact_update(td);
        sched_priority(td);
}

void
sched_userret(struct thread *td)
{
        /*
         * XXX we cheat slightly on the locking here to avoid locking in  
         * the usual case.  Setting td_priority here is essentially an
         * incomplete workaround for not setting it properly elsewhere.
         * Now that some interrupt handlers are threads, not setting it
         * properly elsewhere can clobber it in the window between setting
         * it here and returning to user mode, so don't waste time setting
         * it perfectly here.
         */
        KASSERT((td->td_flags & TDF_BORROWING) == 0,
            ("thread with borrowed priority returning to userland"));
        if (td->td_priority != td->td_user_pri) {
                mtx_lock_spin(&sched_lock);
                td->td_priority = td->td_user_pri;
                td->td_base_pri = td->td_user_pri;
                mtx_unlock_spin(&sched_lock);
        }
}

void
sched_clock(struct thread *td)
{
        struct tdq *tdq;
        struct td_sched *ts;

        mtx_assert(&sched_lock, MA_OWNED);
#ifdef SMP
        sched_smp_tick(td);
#endif
        tdq = TDQ_SELF();
        /*
         * Advance the insert index once for each tick to ensure that all
         * threads get a chance to run.
         */
        if (tdq->tdq_idx == tdq->tdq_ridx) {
                tdq->tdq_idx = (tdq->tdq_idx + 1) % RQ_NQS;
                if (TAILQ_EMPTY(&tdq->tdq_timeshare.rq_queues[tdq->tdq_ridx]))
                        tdq->tdq_ridx = tdq->tdq_idx;
        }
        ts = td->td_sched;
        /*
         * We only do slicing code for TIMESHARE threads.
         */
        if (td->td_pri_class != PRI_TIMESHARE)
                return;
        /*
         * We used a tick; charge it to the thread so that we can compute our
         * interactivity.
         */
        td->td_sched->skg_runtime += tickincr;
        sched_interact_update(td);
        /*
         * We used up one time slice.
         */
        if (--ts->ts_slice > 0)
                return;
        /*
         * We're out of time, recompute priorities and requeue.
         */
        sched_priority(td);
        td->td_flags |= TDF_NEEDRESCHED;
}

int
sched_runnable(void)
{
        struct tdq *tdq;
        int load;

        load = 1;

        tdq = TDQ_SELF();
#ifdef SMP
        if (tdq_busy)
                goto out;
#endif
        if ((curthread->td_flags & TDF_IDLETD) != 0) {
                if (tdq->tdq_load > 0)
                        goto out;
        } else
                if (tdq->tdq_load - 1 > 0)
                        goto out;
        load = 0;
out:
        return (load);
}

struct thread *
sched_choose(void)
{
        struct tdq *tdq;
        struct td_sched *ts;

        mtx_assert(&sched_lock, MA_OWNED);
        tdq = TDQ_SELF();
#ifdef SMP
restart:
#endif
        ts = tdq_choose(tdq);
        if (ts) {
#ifdef SMP
                if (ts->ts_thread->td_priority > PRI_MIN_IDLE)
                        if (tdq_idled(tdq) == 0)
                                goto restart;
#endif
                tdq_runq_rem(tdq, ts);
                return (ts->ts_thread);
        }
#ifdef SMP
        if (tdq_idled(tdq) == 0)
                goto restart;
#endif
        return (PCPU_GET(idlethread));
}

static int
sched_preempt(struct thread *td)
{
        struct thread *ctd;
        int cpri;
        int pri;

        ctd = curthread;
        pri = td->td_priority;
        cpri = ctd->td_priority;
        if (panicstr != NULL || pri >= cpri || cold || TD_IS_INHIBITED(ctd))
                return (0);
        /*
         * Always preempt IDLE threads.  Otherwise only if the preempting
         * thread is an ithread.
         */
        if (pri > PRI_MAX_ITHD && cpri < PRI_MIN_IDLE)
                return (0);
        if (ctd->td_critnest > 1) {
                CTR1(KTR_PROC, "sched_preempt: in critical section %d",
                    ctd->td_critnest);
                ctd->td_owepreempt = 1;
                return (0);
        }
        /*
         * Thread is runnable but not yet put on system run queue.
         */
        MPASS(TD_ON_RUNQ(td));
        TD_SET_RUNNING(td);
        CTR3(KTR_PROC, "preempting to thread %p (pid %d, %s)\n", td,
            td->td_proc->p_pid, td->td_proc->p_comm);
        mi_switch(SW_INVOL|SW_PREEMPT, td);
        return (1);
}

void
sched_add(struct thread *td, int flags)
{
        struct tdq *tdq;
        struct td_sched *ts;
        int preemptive;
        int class;
#ifdef SMP
        int cpuid;
        int cpumask;
#endif
        ts = td->td_sched;

        mtx_assert(&sched_lock, MA_OWNED);
        CTR5(KTR_SCHED, "sched_add: %p(%s) prio %d by %p(%s)",
            td, td->td_proc->p_comm, td->td_priority, curthread,
            curthread->td_proc->p_comm);
        KASSERT((td->td_inhibitors == 0),
            ("sched_add: trying to run inhibited thread"));
        KASSERT((TD_CAN_RUN(td) || TD_IS_RUNNING(td)),
            ("sched_add: bad thread state"));
        KASSERT(td->td_proc->p_sflag & PS_INMEM,
            ("sched_add: process swapped out"));
        KASSERT(ts->ts_runq == NULL,
            ("sched_add: thread %p is still assigned to a run queue", td));
        TD_SET_RUNQ(td);
        tdq = TDQ_SELF();
        class = PRI_BASE(td->td_pri_class);
        preemptive = !(flags & SRQ_YIELDING);
        /*
         * Recalculate the priority before we select the target cpu or
         * run-queue.
         */
        if (class == PRI_TIMESHARE)
                sched_priority(td);
        if (ts->ts_slice == 0)
                ts->ts_slice = sched_slice;
#ifdef SMP
        cpuid = PCPU_GET(cpuid);
        /*
         * Pick the destination cpu and if it isn't ours transfer to the
         * target cpu.
         */
        if (THREAD_CAN_MIGRATE(td)) {
                if (td->td_priority <= PRI_MAX_ITHD) {
                        CTR2(KTR_ULE, "ithd %d < %d",
                            td->td_priority, PRI_MAX_ITHD);
                        ts->ts_cpu = cpuid;
                }
                if (pick_pri)
                        ts->ts_cpu = tdq_pickpri(tdq, ts, flags);
                else
                        ts->ts_cpu = tdq_pickidle(tdq, ts);
        } else
                CTR1(KTR_ULE, "pinned %d", td->td_pinned);
        if (ts->ts_cpu != cpuid)
                preemptive = 0;
        tdq = TDQ_CPU(ts->ts_cpu);
        cpumask = 1 << ts->ts_cpu;
        /*
         * If we had been idle, clear our bit in the group and potentially
         * the global bitmap.
         */
        if ((class != PRI_IDLE && class != PRI_ITHD) &&
            (tdq->tdq_group->tdg_idlemask & cpumask) != 0) {
                /*
                 * Check to see if our group is unidling, and if so, remove it
                 * from the global idle mask.
                 */
                if (tdq->tdq_group->tdg_idlemask ==
                    tdq->tdq_group->tdg_cpumask)
                        atomic_clear_int(&tdq_idle, tdq->tdq_group->tdg_mask);
                /*
                 * Now remove ourselves from the group specific idle mask.
                 */
                tdq->tdq_group->tdg_idlemask &= ~cpumask;
        }
#endif
        /*
         * Pick the run queue based on priority.
         */
        if (td->td_priority <= PRI_MAX_REALTIME)
                ts->ts_runq = &tdq->tdq_realtime;
        else if (td->td_priority <= PRI_MAX_TIMESHARE)
                ts->ts_runq = &tdq->tdq_timeshare;
        else
                ts->ts_runq = &tdq->tdq_idle;
        if (preemptive && sched_preempt(td))
                return;
        tdq_runq_add(tdq, ts, flags);
        tdq_load_add(tdq, ts);
#ifdef SMP
        if (ts->ts_cpu != cpuid) {
                tdq_notify(ts);
                return;
        }
#endif
        if (td->td_priority < curthread->td_priority)
                curthread->td_flags |= TDF_NEEDRESCHED;
}

void
sched_rem(struct thread *td)
{
        struct tdq *tdq;
        struct td_sched *ts;

        CTR5(KTR_SCHED, "sched_rem: %p(%s) prio %d by %p(%s)",
            td, td->td_proc->p_comm, td->td_priority, curthread,
            curthread->td_proc->p_comm);
        mtx_assert(&sched_lock, MA_OWNED);
        ts = td->td_sched;
        KASSERT(TD_ON_RUNQ(td),
            ("sched_rem: thread not on run queue"));

        tdq = TDQ_CPU(ts->ts_cpu);
        tdq_runq_rem(tdq, ts);
        tdq_load_rem(tdq, ts);
        TD_SET_CAN_RUN(td);
}

fixpt_t
sched_pctcpu(struct thread *td)
{
        fixpt_t pctcpu;
        struct td_sched *ts;

        pctcpu = 0;
        ts = td->td_sched;
        if (ts == NULL)
                return (0);

        mtx_lock_spin(&sched_lock);
        if (ts->ts_ticks) {
                int rtick;

                sched_pctcpu_update(ts);
                /* How many rtick per second ? */
                rtick = min(SCHED_TICK_HZ(ts) / SCHED_TICK_SECS, hz);
                pctcpu = (FSCALE * ((FSCALE * rtick)/hz)) >> FSHIFT;
        }
        td->td_proc->p_swtime = ts->ts_ltick - ts->ts_ftick;
        mtx_unlock_spin(&sched_lock);

        return (pctcpu);
}

void
sched_bind(struct thread *td, int cpu)
{
        struct td_sched *ts;

        mtx_assert(&sched_lock, MA_OWNED);
        ts = td->td_sched;
        if (ts->ts_flags & TSF_BOUND)
                sched_unbind(td);
        ts->ts_flags |= TSF_BOUND;
#ifdef SMP
        sched_pin();
        if (PCPU_GET(cpuid) == cpu)
                return;
        ts->ts_cpu = cpu;
        /* When we return from mi_switch we'll be on the correct cpu. */
        mi_switch(SW_VOL, NULL);
#endif
}

void
sched_unbind(struct thread *td)
{
        struct td_sched *ts;

        mtx_assert(&sched_lock, MA_OWNED);
        ts = td->td_sched;
        if ((ts->ts_flags & TSF_BOUND) == 0)
                return;
        ts->ts_flags &= ~TSF_BOUND;
#ifdef SMP
        sched_unpin();
#endif
}

int
sched_is_bound(struct thread *td)
{
        mtx_assert(&sched_lock, MA_OWNED);
        return (td->td_sched->ts_flags & TSF_BOUND);
}

void
sched_relinquish(struct thread *td)
{
        mtx_lock_spin(&sched_lock);
        if (td->td_pri_class == PRI_TIMESHARE)
                sched_prio(td, PRI_MAX_TIMESHARE);
        mi_switch(SW_VOL, NULL);
        mtx_unlock_spin(&sched_lock);
}

int
sched_load(void)
{
#ifdef SMP
        int total;
        int i;

        total = 0;
        for (i = 0; i <= tdg_maxid; i++)
                total += TDQ_GROUP(i)->tdg_load;
        return (total);
#else
        return (TDQ_SELF()->tdq_sysload);
#endif
}

int
sched_sizeof_proc(void)
{
        return (sizeof(struct proc));
}

int
sched_sizeof_thread(void)
{
        return (sizeof(struct thread) + sizeof(struct td_sched));
}

void
sched_tick(void)
{
        struct td_sched *ts;

        ts = curthread->td_sched;
        /* Adjust ticks for pctcpu */
        ts->ts_ticks += 1 << SCHED_TICK_SHIFT;
        ts->ts_ltick = ticks;
        /*
         * Update if we've exceeded our desired tick threshhold by over one
         * second.
         */
        if (ts->ts_ftick + SCHED_TICK_MAX < ts->ts_ltick)
                sched_pctcpu_update(ts);
}

/*
 * The actual idle process.
 */
void
sched_idletd(void *dummy)
{
        struct proc *p;
        struct thread *td;

        td = curthread;
        p = td->td_proc;
        mtx_assert(&Giant, MA_NOTOWNED);
        /* ULE Relies on preemption for idle interruption. */
        for (;;)
                cpu_idle();
}

static SYSCTL_NODE(_kern, OID_AUTO, sched, CTLFLAG_RW, 0, "Scheduler");
SYSCTL_STRING(_kern_sched, OID_AUTO, name, CTLFLAG_RD, "ule", 0,
    "Scheduler name");
SYSCTL_INT(_kern_sched, OID_AUTO, slice, CTLFLAG_RW, &sched_slice, 0, "");
SYSCTL_INT(_kern_sched, OID_AUTO, interact, CTLFLAG_RW, &sched_interact, 0, "");
SYSCTL_INT(_kern_sched, OID_AUTO, tickincr, CTLFLAG_RD, &tickincr, 0, "");
SYSCTL_INT(_kern_sched, OID_AUTO, realstathz, CTLFLAG_RD, &realstathz, 0, "");
#ifdef SMP
SYSCTL_INT(_kern_sched, OID_AUTO, pick_pri, CTLFLAG_RW, &pick_pri, 0, "");
SYSCTL_INT(_kern_sched, OID_AUTO, pick_pri_affinity, CTLFLAG_RW,
    &affinity, 0, "");
SYSCTL_INT(_kern_sched, OID_AUTO, pick_pri_tryself, CTLFLAG_RW,
    &tryself, 0, "");
SYSCTL_INT(_kern_sched, OID_AUTO, pick_pri_tryselfidle, CTLFLAG_RW,
    &tryselfidle, 0, "");
SYSCTL_INT(_kern_sched, OID_AUTO, balance, CTLFLAG_RW, &rebalance, 0, "");
SYSCTL_INT(_kern_sched, OID_AUTO, ipi_preempt, CTLFLAG_RW, &ipi_preempt, 0, "");
SYSCTL_INT(_kern_sched, OID_AUTO, ipi_ast, CTLFLAG_RW, &ipi_ast, 0, "");
SYSCTL_INT(_kern_sched, OID_AUTO, ipi_thresh, CTLFLAG_RW, &ipi_thresh, 0, "");
SYSCTL_INT(_kern_sched, OID_AUTO, steal_htt, CTLFLAG_RW, &steal_htt, 0, "");
SYSCTL_INT(_kern_sched, OID_AUTO, steal_busy, CTLFLAG_RW, &steal_busy, 0, "");
SYSCTL_INT(_kern_sched, OID_AUTO, busy_thresh, CTLFLAG_RW, &busy_thresh, 0, "");
#endif

/* ps compat */
static fixpt_t  ccpu = 0.95122942450071400909 * FSCALE; /* exp(-1/20) */
SYSCTL_INT(_kern, OID_AUTO, ccpu, CTLFLAG_RD, &ccpu, 0, "");


#define KERN_SWITCH_INCLUDE 1
#include "kern/kern_switch.c"