2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
4 * Copyright (c) 2001-2002 Luigi Rizzo
6 * Supported by: the Xorp Project (www.xorp.org)
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 #include <sys/cdefs.h>
31 __FBSDID("$FreeBSD$");
33 #include "opt_device_polling.h"
35 #include <sys/param.h>
36 #include <sys/systm.h>
37 #include <sys/kernel.h>
38 #include <sys/kthread.h>
40 #include <sys/epoch.h>
41 #include <sys/eventhandler.h>
42 #include <sys/resourcevar.h>
43 #include <sys/sched.h>
44 #include <sys/socket.h> /* needed by net/if.h */
45 #include <sys/sockio.h>
46 #include <sys/sysctl.h>
47 #include <sys/syslog.h>
50 #include <net/if_var.h>
51 #include <net/netisr.h> /* for NETISR_POLL */
54 void hardclock_device_poll(void); /* hook from hardclock */
56 static struct mtx poll_mtx;
59 * Polling support for [network] device drivers.
61 * Drivers which support this feature can register with the
64 * If registration is successful, the driver must disable interrupts,
65 * and further I/O is performed through the handler, which is invoked
66 * (at least once per clock tick) with 3 arguments: the "arg" passed at
67 * register time (a struct ifnet pointer), a command, and a "count" limit.
69 * The command can be one of the following:
70 * POLL_ONLY: quick move of "count" packets from input/output queues.
71 * POLL_AND_CHECK_STATUS: as above, plus check status registers or do
72 * other more expensive operations. This command is issued periodically
73 * but less frequently than POLL_ONLY.
75 * The count limit specifies how much work the handler can do during the
76 * call -- typically this is the number of packets to be received, or
77 * transmitted, etc. (drivers are free to interpret this number, as long
78 * as the max time spent in the function grows roughly linearly with the
81 * Polling is enabled and disabled via setting IFCAP_POLLING flag on
82 * the interface. The driver ioctl handler should register interface
83 * with polling and disable interrupts, if registration was successful.
85 * A second variable controls the sharing of CPU between polling/kernel
86 * network processing, and other activities (typically userlevel tasks):
87 * kern.polling.user_frac (between 0 and 100, default 50) sets the share
88 * of CPU allocated to user tasks. CPU is allocated proportionally to the
89 * shares, by dynamically adjusting the "count" (poll_burst).
91 * Other parameters can should be left to their default values.
92 * The following constraints hold
94 * 1 <= poll_each_burst <= poll_burst <= poll_burst_max
95 * MIN_POLL_BURST_MAX <= poll_burst_max <= MAX_POLL_BURST_MAX
98 #define MIN_POLL_BURST_MAX 10
99 #define MAX_POLL_BURST_MAX 20000
101 static uint32_t poll_burst = 5;
102 static uint32_t poll_burst_max = 150; /* good for 100Mbit net and HZ=1000 */
103 static uint32_t poll_each_burst = 5;
105 static SYSCTL_NODE(_kern, OID_AUTO, polling, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
106 "Device polling parameters");
108 SYSCTL_UINT(_kern_polling, OID_AUTO, burst, CTLFLAG_RD,
109 &poll_burst, 0, "Current polling burst size");
111 static int netisr_poll_scheduled;
112 static int netisr_pollmore_scheduled;
113 static int poll_shutting_down;
115 static int poll_burst_max_sysctl(SYSCTL_HANDLER_ARGS)
117 uint32_t val = poll_burst_max;
120 error = sysctl_handle_int(oidp, &val, 0, req);
121 if (error || !req->newptr )
123 if (val < MIN_POLL_BURST_MAX || val > MAX_POLL_BURST_MAX)
127 poll_burst_max = val;
128 if (poll_burst > poll_burst_max)
129 poll_burst = poll_burst_max;
130 if (poll_each_burst > poll_burst_max)
131 poll_each_burst = MIN_POLL_BURST_MAX;
132 mtx_unlock(&poll_mtx);
136 SYSCTL_PROC(_kern_polling, OID_AUTO, burst_max,
137 CTLTYPE_UINT | CTLFLAG_RW | CTLFLAG_MPSAFE, 0, sizeof(uint32_t),
138 poll_burst_max_sysctl, "I",
139 "Max Polling burst size");
141 static int poll_each_burst_sysctl(SYSCTL_HANDLER_ARGS)
143 uint32_t val = poll_each_burst;
146 error = sysctl_handle_int(oidp, &val, 0, req);
147 if (error || !req->newptr )
153 if (val > poll_burst_max) {
154 mtx_unlock(&poll_mtx);
157 poll_each_burst = val;
158 mtx_unlock(&poll_mtx);
162 SYSCTL_PROC(_kern_polling, OID_AUTO, each_burst,
163 CTLTYPE_UINT | CTLFLAG_RW | CTLFLAG_MPSAFE, 0, sizeof(uint32_t),
164 poll_each_burst_sysctl, "I",
165 "Max size of each burst");
167 static uint32_t poll_in_idle_loop=0; /* do we poll in idle loop ? */
168 SYSCTL_UINT(_kern_polling, OID_AUTO, idle_poll, CTLFLAG_RW,
169 &poll_in_idle_loop, 0, "Enable device polling in idle loop");
171 static uint32_t user_frac = 50;
172 static int user_frac_sysctl(SYSCTL_HANDLER_ARGS)
174 uint32_t val = user_frac;
177 error = sysctl_handle_int(oidp, &val, 0, req);
178 if (error || !req->newptr )
185 mtx_unlock(&poll_mtx);
189 SYSCTL_PROC(_kern_polling, OID_AUTO, user_frac,
190 CTLTYPE_UINT | CTLFLAG_RW | CTLFLAG_MPSAFE, 0, sizeof(uint32_t),
191 user_frac_sysctl, "I",
192 "Desired user fraction of cpu time");
194 static uint32_t reg_frac_count = 0;
195 static uint32_t reg_frac = 20 ;
196 static int reg_frac_sysctl(SYSCTL_HANDLER_ARGS)
198 uint32_t val = reg_frac;
201 error = sysctl_handle_int(oidp, &val, 0, req);
202 if (error || !req->newptr )
204 if (val < 1 || val > hz)
209 if (reg_frac_count >= reg_frac)
211 mtx_unlock(&poll_mtx);
215 SYSCTL_PROC(_kern_polling, OID_AUTO, reg_frac,
216 CTLTYPE_UINT | CTLFLAG_RW | CTLFLAG_MPSAFE, 0, sizeof(uint32_t),
217 reg_frac_sysctl, "I",
218 "Every this many cycles check registers");
220 static uint32_t short_ticks;
221 SYSCTL_UINT(_kern_polling, OID_AUTO, short_ticks, CTLFLAG_RD,
222 &short_ticks, 0, "Hardclock ticks shorter than they should be");
224 static uint32_t lost_polls;
225 SYSCTL_UINT(_kern_polling, OID_AUTO, lost_polls, CTLFLAG_RD,
226 &lost_polls, 0, "How many times we would have lost a poll tick");
228 static uint32_t pending_polls;
229 SYSCTL_UINT(_kern_polling, OID_AUTO, pending_polls, CTLFLAG_RD,
230 &pending_polls, 0, "Do we need to poll again");
232 static int residual_burst = 0;
233 SYSCTL_INT(_kern_polling, OID_AUTO, residual_burst, CTLFLAG_RD,
234 &residual_burst, 0, "# of residual cycles in burst");
236 static uint32_t poll_handlers; /* next free entry in pr[]. */
237 SYSCTL_UINT(_kern_polling, OID_AUTO, handlers, CTLFLAG_RD,
238 &poll_handlers, 0, "Number of registered poll handlers");
240 static uint32_t phase;
241 SYSCTL_UINT(_kern_polling, OID_AUTO, phase, CTLFLAG_RD,
242 &phase, 0, "Polling phase");
244 static uint32_t suspect;
245 SYSCTL_UINT(_kern_polling, OID_AUTO, suspect, CTLFLAG_RD,
246 &suspect, 0, "suspect event");
248 static uint32_t stalled;
249 SYSCTL_UINT(_kern_polling, OID_AUTO, stalled, CTLFLAG_RD,
250 &stalled, 0, "potential stalls");
252 static uint32_t idlepoll_sleeping; /* idlepoll is sleeping */
253 SYSCTL_UINT(_kern_polling, OID_AUTO, idlepoll_sleeping, CTLFLAG_RD,
254 &idlepoll_sleeping, 0, "idlepoll is sleeping");
256 #define POLL_LIST_LEN 128
258 poll_handler_t *handler;
262 static struct pollrec pr[POLL_LIST_LEN];
265 poll_shutdown(void *arg, int howto)
268 poll_shutting_down = 1;
272 init_device_poll(void)
275 mtx_init(&poll_mtx, "polling", NULL, MTX_DEF);
276 EVENTHANDLER_REGISTER(shutdown_post_sync, poll_shutdown, NULL,
279 SYSINIT(device_poll, SI_SUB_SOFTINTR, SI_ORDER_MIDDLE, init_device_poll, NULL);
282 * Hook from hardclock. Tries to schedule a netisr, but keeps track
283 * of lost ticks due to the previous handler taking too long.
284 * Normally, this should not happen, because polling handler should
285 * run for a short time. However, in some cases (e.g. when there are
286 * changes in link status etc.) the drivers take a very long time
287 * (even in the order of milliseconds) to reset and reconfigure the
288 * device, causing apparent lost polls.
290 * The first part of the code is just for debugging purposes, and tries
291 * to count how often hardclock ticks are shorter than they should,
292 * meaning either stray interrupts or delayed events.
295 hardclock_device_poll(void)
297 static struct timeval prev_t, t;
300 if (poll_handlers == 0 || poll_shutting_down)
304 delta = (t.tv_usec - prev_t.tv_usec) +
305 (t.tv_sec - prev_t.tv_sec)*1000000;
306 if (delta * hz < 500000)
311 if (pending_polls > 100) {
313 * Too much, assume it has stalled (not always true
314 * see comment above).
325 netisr_poll_scheduled = 1;
326 netisr_pollmore_scheduled = 1;
330 if (pending_polls++ > 0)
335 * ether_poll is called from the idle loop.
338 ether_poll(int count)
340 struct epoch_tracker et;
345 if (count > poll_each_burst)
346 count = poll_each_burst;
349 for (i = 0 ; i < poll_handlers ; i++)
350 pr[i].handler(pr[i].ifp, POLL_ONLY, count);
353 mtx_unlock(&poll_mtx);
357 * netisr_pollmore is called after other netisr's, possibly scheduling
358 * another NETISR_POLL call, or adapting the burst size for the next cycle.
360 * It is very bad to fetch large bursts of packets from a single card at once,
361 * because the burst could take a long time to be completely processed, or
362 * could saturate the intermediate queue (ipintrq or similar) leading to
363 * losses or unfairness. To reduce the problem, and also to account better for
364 * time spent in network-related processing, we split the burst in smaller
365 * chunks of fixed size, giving control to the other netisr's between chunks.
366 * This helps in improving the fairness, reducing livelock (because we
367 * emulate more closely the "process to completion" that we have with
368 * fastforwarding) and accounting for the work performed in low level
369 * handling and forwarding.
372 static struct timeval poll_start_t;
375 netisr_pollmore(void)
380 if (poll_handlers == 0)
384 if (!netisr_pollmore_scheduled) {
385 mtx_unlock(&poll_mtx);
388 netisr_pollmore_scheduled = 0;
390 if (residual_burst > 0) {
391 netisr_poll_scheduled = 1;
392 netisr_pollmore_scheduled = 1;
394 mtx_unlock(&poll_mtx);
395 /* will run immediately on return, followed by netisrs */
398 /* here we can account time spent in netisr's in this tick */
400 kern_load = (t.tv_usec - poll_start_t.tv_usec) +
401 (t.tv_sec - poll_start_t.tv_sec)*1000000; /* us */
402 kern_load = (kern_load * hz) / 10000; /* 0..100 */
403 if (kern_load > (100 - user_frac)) { /* try decrease ticks */
407 if (poll_burst < poll_burst_max)
412 if (pending_polls == 0) /* we are done */
416 * Last cycle was long and caused us to miss one or more
417 * hardclock ticks. Restart processing again, but slightly
418 * reduce the burst size to prevent that this happens again.
420 poll_burst -= (poll_burst / 8);
423 netisr_poll_scheduled = 1;
424 netisr_pollmore_scheduled = 1;
428 mtx_unlock(&poll_mtx);
432 * netisr_poll is typically scheduled once per tick.
438 enum poll_cmd arg = POLL_ONLY;
442 if (poll_handlers == 0)
446 if (!netisr_poll_scheduled) {
447 mtx_unlock(&poll_mtx);
450 netisr_poll_scheduled = 0;
452 if (residual_burst == 0) { /* first call in this tick */
453 microuptime(&poll_start_t);
454 if (++reg_frac_count == reg_frac) {
455 arg = POLL_AND_CHECK_STATUS;
459 residual_burst = poll_burst;
461 cycles = (residual_burst < poll_each_burst) ?
462 residual_burst : poll_each_burst;
463 residual_burst -= cycles;
465 for (i = 0 ; i < poll_handlers ; i++)
466 pr[i].handler(pr[i].ifp, arg, cycles);
469 mtx_unlock(&poll_mtx);
473 * Try to register routine for polling. Returns 0 if successful
474 * (and polling should be enabled), error code otherwise.
475 * A device is not supposed to register itself multiple times.
477 * This is called from within the *_ioctl() functions.
480 ether_poll_register(poll_handler_t *h, if_t ifp)
484 KASSERT(h != NULL, ("%s: handler is NULL", __func__));
485 KASSERT(ifp != NULL, ("%s: ifp is NULL", __func__));
488 if (poll_handlers >= POLL_LIST_LEN) {
490 * List full, cannot register more entries.
491 * This should never happen; if it does, it is probably a
492 * broken driver trying to register multiple times. Checking
493 * this at runtime is expensive, and won't solve the problem
494 * anyways, so just report a few times and then give up.
496 static int verbose = 10 ;
498 log(LOG_ERR, "poll handlers list full, "
499 "maybe a broken driver ?\n");
502 mtx_unlock(&poll_mtx);
503 return (ENOMEM); /* no polling for you */
506 for (i = 0 ; i < poll_handlers ; i++)
507 if (pr[i].ifp == ifp && pr[i].handler != NULL) {
508 mtx_unlock(&poll_mtx);
509 log(LOG_DEBUG, "ether_poll_register: %s: handler"
510 " already registered\n", if_name(ifp));
514 pr[poll_handlers].handler = h;
515 pr[poll_handlers].ifp = ifp;
517 mtx_unlock(&poll_mtx);
518 if (idlepoll_sleeping)
519 wakeup(&idlepoll_sleeping);
524 * Remove interface from the polling list. Called from *_ioctl(), too.
527 ether_poll_deregister(if_t ifp)
531 KASSERT(ifp != NULL, ("%s: ifp is NULL", __func__));
535 for (i = 0 ; i < poll_handlers ; i++)
536 if (pr[i].ifp == ifp) /* found it */
538 if (i == poll_handlers) {
539 log(LOG_DEBUG, "ether_poll_deregister: %s: not found!\n",
541 mtx_unlock(&poll_mtx);
545 if (i < poll_handlers) { /* Last entry replaces this one. */
546 pr[i].handler = pr[poll_handlers].handler;
547 pr[i].ifp = pr[poll_handlers].ifp;
549 mtx_unlock(&poll_mtx);
556 struct thread *td = curthread;
559 rtp.prio = RTP_PRIO_MAX; /* lowest priority */
560 rtp.type = RTP_PRIO_IDLE;
561 PROC_SLOCK(td->td_proc);
562 rtp_to_pri(&rtp, td);
563 PROC_SUNLOCK(td->td_proc);
566 if (poll_in_idle_loop && poll_handlers > 0) {
567 idlepoll_sleeping = 0;
568 ether_poll(poll_each_burst);
569 sched_relinquish(td);
571 idlepoll_sleeping = 1;
572 tsleep(&idlepoll_sleeping, 0, "pollid", hz * 3);
577 static struct proc *idlepoll;
578 static struct kproc_desc idlepoll_kp = {
583 SYSINIT(idlepoll, SI_SUB_KTHREAD_VM, SI_ORDER_ANY, kproc_start,