2 * Copyright (c) 2001-2002 Luigi Rizzo
4 * Supported by: the Xorp Project (www.xorp.org)
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
16 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28 #include <sys/cdefs.h>
29 __FBSDID("$FreeBSD$");
31 #include <sys/param.h>
32 #include <sys/systm.h>
33 #include <sys/kernel.h>
34 #include <sys/socket.h> /* needed by net/if.h */
35 #include <sys/sysctl.h>
37 #include <net/if.h> /* for IFF_* flags */
38 #include <net/netisr.h> /* for NETISR_POLL */
41 #include <sys/resourcevar.h>
42 #include <sys/kthread.h>
44 static void netisr_poll(void); /* the two netisr handlers */
45 static void netisr_pollmore(void);
47 void hardclock_device_poll(void); /* hook from hardclock */
48 void ether_poll(int); /* polling while in trap */
51 * Polling support for [network] device drivers.
53 * Drivers which support this feature try to register with the
56 * If registration is successful, the driver must disable interrupts,
57 * and further I/O is performed through the handler, which is invoked
58 * (at least once per clock tick) with 3 arguments: the "arg" passed at
59 * register time (a struct ifnet pointer), a command, and a "count" limit.
61 * The command can be one of the following:
62 * POLL_ONLY: quick move of "count" packets from input/output queues.
63 * POLL_AND_CHECK_STATUS: as above, plus check status registers or do
64 * other more expensive operations. This command is issued periodically
65 * but less frequently than POLL_ONLY.
66 * POLL_DEREGISTER: deregister and return to interrupt mode.
68 * The first two commands are only issued if the interface is marked as
69 * 'IFF_UP and IFF_RUNNING', the last one only if IFF_RUNNING is set.
71 * The count limit specifies how much work the handler can do during the
72 * call -- typically this is the number of packets to be received, or
73 * transmitted, etc. (drivers are free to interpret this number, as long
74 * as the max time spent in the function grows roughly linearly with the
77 * Deregistration can be requested by the driver itself (typically in the
78 * *_stop() routine), or by the polling code, by invoking the handler.
80 * Polling can be globally enabled or disabled with the sysctl variable
81 * kern.polling.enable (default is 0, disabled)
83 * A second variable controls the sharing of CPU between polling/kernel
84 * network processing, and other activities (typically userlevel tasks):
85 * kern.polling.user_frac (between 0 and 100, default 50) sets the share
86 * of CPU allocated to user tasks. CPU is allocated proportionally to the
87 * shares, by dynamically adjusting the "count" (poll_burst).
89 * Other parameters can should be left to their default values.
90 * The following constraints hold
92 * 1 <= poll_each_burst <= poll_burst <= poll_burst_max
93 * 0 <= poll_in_trap <= poll_each_burst
94 * MIN_POLL_BURST_MAX <= poll_burst_max <= MAX_POLL_BURST_MAX
97 #define MIN_POLL_BURST_MAX 10
98 #define MAX_POLL_BURST_MAX 1000
100 SYSCTL_NODE(_kern, OID_AUTO, polling, CTLFLAG_RW, 0,
101 "Device polling parameters");
103 static u_int32_t poll_burst = 5;
104 SYSCTL_UINT(_kern_polling, OID_AUTO, burst, CTLFLAG_RW,
105 &poll_burst, 0, "Current polling burst size");
107 static u_int32_t poll_each_burst = 5;
108 SYSCTL_UINT(_kern_polling, OID_AUTO, each_burst, CTLFLAG_RW,
109 &poll_each_burst, 0, "Max size of each burst");
111 static u_int32_t poll_burst_max = 150; /* good for 100Mbit net and HZ=1000 */
112 SYSCTL_UINT(_kern_polling, OID_AUTO, burst_max, CTLFLAG_RW,
113 &poll_burst_max, 0, "Max Polling burst size");
115 static u_int32_t poll_in_idle_loop=0; /* do we poll in idle loop ? */
116 SYSCTL_UINT(_kern_polling, OID_AUTO, idle_poll, CTLFLAG_RW,
117 &poll_in_idle_loop, 0, "Enable device polling in idle loop");
119 u_int32_t poll_in_trap; /* used in trap.c */
120 SYSCTL_UINT(_kern_polling, OID_AUTO, poll_in_trap, CTLFLAG_RW,
121 &poll_in_trap, 0, "Poll burst size during a trap");
123 static u_int32_t user_frac = 50;
124 SYSCTL_UINT(_kern_polling, OID_AUTO, user_frac, CTLFLAG_RW,
125 &user_frac, 0, "Desired user fraction of cpu time");
127 static u_int32_t reg_frac = 20 ;
128 SYSCTL_UINT(_kern_polling, OID_AUTO, reg_frac, CTLFLAG_RW,
129 ®_frac, 0, "Every this many cycles poll register");
131 static u_int32_t short_ticks;
132 SYSCTL_UINT(_kern_polling, OID_AUTO, short_ticks, CTLFLAG_RW,
133 &short_ticks, 0, "Hardclock ticks shorter than they should be");
135 static u_int32_t lost_polls;
136 SYSCTL_UINT(_kern_polling, OID_AUTO, lost_polls, CTLFLAG_RW,
137 &lost_polls, 0, "How many times we would have lost a poll tick");
139 static u_int32_t pending_polls;
140 SYSCTL_UINT(_kern_polling, OID_AUTO, pending_polls, CTLFLAG_RW,
141 &pending_polls, 0, "Do we need to poll again");
143 static int residual_burst = 0;
144 SYSCTL_INT(_kern_polling, OID_AUTO, residual_burst, CTLFLAG_RW,
145 &residual_burst, 0, "# of residual cycles in burst");
147 static u_int32_t poll_handlers; /* next free entry in pr[]. */
148 SYSCTL_UINT(_kern_polling, OID_AUTO, handlers, CTLFLAG_RD,
149 &poll_handlers, 0, "Number of registered poll handlers");
151 static int polling = 0; /* global polling enable */
152 SYSCTL_UINT(_kern_polling, OID_AUTO, enable, CTLFLAG_RW,
153 &polling, 0, "Polling enabled");
155 static u_int32_t phase;
156 SYSCTL_UINT(_kern_polling, OID_AUTO, phase, CTLFLAG_RW,
157 &phase, 0, "Polling phase");
159 static u_int32_t suspect;
160 SYSCTL_UINT(_kern_polling, OID_AUTO, suspect, CTLFLAG_RW,
161 &suspect, 0, "suspect event");
163 static u_int32_t stalled;
164 SYSCTL_UINT(_kern_polling, OID_AUTO, stalled, CTLFLAG_RW,
165 &stalled, 0, "potential stalls");
167 static u_int32_t idlepoll_sleeping; /* idlepoll is sleeping */
168 SYSCTL_UINT(_kern_polling, OID_AUTO, idlepoll_sleeping, CTLFLAG_RD,
169 &idlepoll_sleeping, 0, "idlepoll is sleeping");
172 #define POLL_LIST_LEN 128
174 poll_handler_t *handler;
178 static struct pollrec pr[POLL_LIST_LEN];
181 init_device_poll(void)
184 netisr_register(NETISR_POLL, (netisr_t *)netisr_poll, NULL, 0);
185 netisr_register(NETISR_POLLMORE, (netisr_t *)netisr_pollmore, NULL, 0);
187 SYSINIT(device_poll, SI_SUB_CLOCKS, SI_ORDER_MIDDLE, init_device_poll, NULL)
191 * Hook from hardclock. Tries to schedule a netisr, but keeps track
192 * of lost ticks due to the previous handler taking too long.
193 * Normally, this should not happen, because polling handler should
194 * run for a short time. However, in some cases (e.g. when there are
195 * changes in link status etc.) the drivers take a very long time
196 * (even in the order of milliseconds) to reset and reconfigure the
197 * device, causing apparent lost polls.
199 * The first part of the code is just for debugging purposes, and tries
200 * to count how often hardclock ticks are shorter than they should,
201 * meaning either stray interrupts or delayed events.
204 hardclock_device_poll(void)
206 static struct timeval prev_t, t;
209 if (poll_handlers == 0)
213 delta = (t.tv_usec - prev_t.tv_usec) +
214 (t.tv_sec - prev_t.tv_sec)*1000000;
215 if (delta * hz < 500000)
220 if (pending_polls > 100) {
222 * Too much, assume it has stalled (not always true
223 * see comment above).
234 schednetisrbits(1 << NETISR_POLL | 1 << NETISR_POLLMORE);
237 if (pending_polls++ > 0)
242 * ether_poll is called from the idle loop or from the trap handler.
245 ether_poll(int count)
251 if (count > poll_each_burst)
252 count = poll_each_burst;
253 for (i = 0 ; i < poll_handlers ; i++)
254 if (pr[i].handler && (IFF_UP|IFF_RUNNING) ==
255 (pr[i].ifp->if_flags & (IFF_UP|IFF_RUNNING)) )
256 pr[i].handler(pr[i].ifp, 0, count); /* quick check */
261 * netisr_pollmore is called after other netisr's, possibly scheduling
262 * another NETISR_POLL call, or adapting the burst size for the next cycle.
264 * It is very bad to fetch large bursts of packets from a single card at once,
265 * because the burst could take a long time to be completely processed, or
266 * could saturate the intermediate queue (ipintrq or similar) leading to
267 * losses or unfairness. To reduce the problem, and also to account better for
268 * time spent in network-related processing, we split the burst in smaller
269 * chunks of fixed size, giving control to the other netisr's between chunks.
270 * This helps in improving the fairness, reducing livelock (because we
271 * emulate more closely the "process to completion" that we have with
272 * fastforwarding) and accounting for the work performed in low level
273 * handling and forwarding.
276 static struct timeval poll_start_t;
283 /* XXX run at splhigh() or equivalent */
286 if (residual_burst > 0) {
287 schednetisrbits(1 << NETISR_POLL | 1 << NETISR_POLLMORE);
288 /* will run immediately on return, followed by netisrs */
291 /* here we can account time spent in netisr's in this tick */
293 kern_load = (t.tv_usec - poll_start_t.tv_usec) +
294 (t.tv_sec - poll_start_t.tv_sec)*1000000; /* us */
295 kern_load = (kern_load * hz) / 10000; /* 0..100 */
296 if (kern_load > (100 - user_frac)) { /* try decrease ticks */
300 if (poll_burst < poll_burst_max)
305 if (pending_polls == 0) /* we are done */
309 * Last cycle was long and caused us to miss one or more
310 * hardclock ticks. Restart processing again, but slightly
311 * reduce the burst size to prevent that this happens again.
313 poll_burst -= (poll_burst / 8);
316 schednetisrbits(1 << NETISR_POLL | 1 << NETISR_POLLMORE);
322 * netisr_poll is scheduled by schednetisr when appropriate, typically once
323 * per tick. It is called at splnet() so first thing to do is to upgrade to
324 * splimp(), and call all registered handlers.
329 static int reg_frac_count;
331 enum poll_cmd arg = POLL_ONLY;
335 if (residual_burst == 0) { /* first call in this tick */
336 microuptime(&poll_start_t);
338 * Check that paremeters are consistent with runtime
339 * variables. Some of these tests could be done at sysctl
340 * time, but the savings would be very limited because we
341 * still have to check against reg_frac_count and
342 * poll_each_burst. So, instead of writing separate sysctl
343 * handlers, we do all here.
348 else if (reg_frac < 1)
350 if (reg_frac_count > reg_frac)
351 reg_frac_count = reg_frac - 1;
352 if (reg_frac_count-- == 0) {
353 arg = POLL_AND_CHECK_STATUS;
354 reg_frac_count = reg_frac - 1;
356 if (poll_burst_max < MIN_POLL_BURST_MAX)
357 poll_burst_max = MIN_POLL_BURST_MAX;
358 else if (poll_burst_max > MAX_POLL_BURST_MAX)
359 poll_burst_max = MAX_POLL_BURST_MAX;
361 if (poll_each_burst < 1)
363 else if (poll_each_burst > poll_burst_max)
364 poll_each_burst = poll_burst_max;
366 if (poll_burst > poll_burst_max)
367 poll_burst = poll_burst_max;
368 residual_burst = poll_burst;
370 cycles = (residual_burst < poll_each_burst) ?
371 residual_burst : poll_each_burst;
372 residual_burst -= cycles;
375 for (i = 0 ; i < poll_handlers ; i++)
376 if (pr[i].handler && (IFF_UP|IFF_RUNNING) ==
377 (pr[i].ifp->if_flags & (IFF_UP|IFF_RUNNING)) )
378 pr[i].handler(pr[i].ifp, arg, cycles);
379 } else { /* unregister */
380 for (i = 0 ; i < poll_handlers ; i++) {
382 pr[i].ifp->if_flags & IFF_RUNNING) {
383 pr[i].ifp->if_flags &= ~IFF_POLLING;
384 pr[i].handler(pr[i].ifp, POLL_DEREGISTER, 1);
391 /* on -stable, schednetisr(NETISR_POLLMORE); */
397 * Try to register routine for polling. Returns 1 if successful
398 * (and polling should be enabled), 0 otherwise.
399 * A device is not supposed to register itself multiple times.
401 * This is called from within the *_intr() functions, so we do not need
405 ether_poll_register(poll_handler_t *h, struct ifnet *ifp)
409 if (polling == 0) /* polling disabled, cannot register */
411 if (h == NULL || ifp == NULL) /* bad arguments */
413 if ( !(ifp->if_flags & IFF_UP) ) /* must be up */
415 if (ifp->if_flags & IFF_POLLING) /* already polling */
419 if (poll_handlers >= POLL_LIST_LEN) {
421 * List full, cannot register more entries.
422 * This should never happen; if it does, it is probably a
423 * broken driver trying to register multiple times. Checking
424 * this at runtime is expensive, and won't solve the problem
425 * anyways, so just report a few times and then give up.
427 static int verbose = 10 ;
430 printf("poll handlers list full, "
431 "maybe a broken driver ?\n");
434 return 0; /* no polling for you */
437 pr[poll_handlers].handler = h;
438 pr[poll_handlers].ifp = ifp;
440 ifp->if_flags |= IFF_POLLING;
442 if (idlepoll_sleeping)
443 wakeup(&idlepoll_sleeping);
444 return 1; /* polling enabled in next call */
448 * Remove interface from the polling list. Normally called by *_stop().
449 * It is not an error to call it with IFF_POLLING clear, the call is
450 * sufficiently rare to be preferable to save the space for the extra
451 * test in each driver in exchange of one additional function call.
454 ether_poll_deregister(struct ifnet *ifp)
459 if ( !ifp || !(ifp->if_flags & IFF_POLLING) ) {
463 for (i = 0 ; i < poll_handlers ; i++)
464 if (pr[i].ifp == ifp) /* found it */
466 ifp->if_flags &= ~IFF_POLLING; /* found or not... */
467 if (i == poll_handlers) {
469 printf("ether_poll_deregister: ifp not found!!!\n");
473 if (i < poll_handlers) { /* Last entry replaces this one. */
474 pr[i].handler = pr[poll_handlers].handler;
475 pr[i].ifp = pr[poll_handlers].ifp;
484 struct thread *td = curthread;
488 rtp.prio = RTP_PRIO_MAX; /* lowest priority */
489 rtp.type = RTP_PRIO_IDLE;
490 mtx_lock_spin(&sched_lock);
491 rtp_to_pri(&rtp, td->td_ksegrp);
492 pri = td->td_priority;
493 mtx_unlock_spin(&sched_lock);
496 if (poll_in_idle_loop && poll_handlers > 0) {
497 idlepoll_sleeping = 0;
499 ether_poll(poll_each_burst);
501 mtx_assert(&Giant, MA_NOTOWNED);
502 mtx_lock_spin(&sched_lock);
503 mi_switch(SW_VOL, NULL);
504 mtx_unlock_spin(&sched_lock);
506 idlepoll_sleeping = 1;
507 tsleep(&idlepoll_sleeping, pri, "pollid", hz * 3);
512 static struct proc *idlepoll;
513 static struct kproc_desc idlepoll_kp = {
518 SYSINIT(idlepoll, SI_SUB_KTHREAD_VM, SI_ORDER_ANY, kproc_start, &idlepoll_kp)