1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause
3 *
4 * Copyright (c) 2001-2002 Luigi Rizzo
5 *
6 * Supported by: the Xorp Project (www.xorp.org)
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
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.
16 *
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
27 * SUCH DAMAGE.
28 */
29
30 #include <sys/cdefs.h>
31 #include "opt_device_polling.h"
32
33 #include <sys/param.h>
34 #include <sys/systm.h>
35 #include <sys/kernel.h>
36 #include <sys/kthread.h>
37 #include <sys/proc.h>
38 #include <sys/epoch.h>
39 #include <sys/eventhandler.h>
40 #include <sys/resourcevar.h>
41 #include <sys/sched.h>
42 #include <sys/socket.h> /* needed by net/if.h */
43 #include <sys/sockio.h>
44 #include <sys/sysctl.h>
45 #include <sys/syslog.h>
46
47 #include <net/if.h>
48 #include <net/if_var.h>
49 #include <net/netisr.h> /* for NETISR_POLL */
50 #include <net/vnet.h>
51
52 void hardclock_device_poll(void); /* hook from hardclock */
53
54 static struct mtx poll_mtx;
55
56 /*
57 * Polling support for [network] device drivers.
58 *
59 * Drivers which support this feature can register with the
60 * polling code.
61 *
62 * If registration is successful, the driver must disable interrupts,
63 * and further I/O is performed through the handler, which is invoked
64 * (at least once per clock tick) with 3 arguments: the "arg" passed at
65 * register time (a struct ifnet pointer), a command, and a "count" limit.
66 *
67 * The command can be one of the following:
68 * POLL_ONLY: quick move of "count" packets from input/output queues.
69 * POLL_AND_CHECK_STATUS: as above, plus check status registers or do
70 * other more expensive operations. This command is issued periodically
71 * but less frequently than POLL_ONLY.
72 *
73 * The count limit specifies how much work the handler can do during the
74 * call -- typically this is the number of packets to be received, or
75 * transmitted, etc. (drivers are free to interpret this number, as long
76 * as the max time spent in the function grows roughly linearly with the
77 * count).
78 *
79 * Polling is enabled and disabled via setting IFCAP_POLLING flag on
80 * the interface. The driver ioctl handler should register interface
81 * with polling and disable interrupts, if registration was successful.
82 *
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).
88 *
89 * Other parameters can should be left to their default values.
90 * The following constraints hold
91 *
92 * 1 <= poll_each_burst <= poll_burst <= poll_burst_max
93 * MIN_POLL_BURST_MAX <= poll_burst_max <= MAX_POLL_BURST_MAX
94 */
95
96 #define MIN_POLL_BURST_MAX 10
97 #define MAX_POLL_BURST_MAX 20000
98
99 static uint32_t poll_burst = 5;
100 static uint32_t poll_burst_max = 150; /* good for 100Mbit net and HZ=1000 */
101 static uint32_t poll_each_burst = 5;
102
103 static SYSCTL_NODE(_kern, OID_AUTO, polling, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
104 "Device polling parameters");
105
106 SYSCTL_UINT(_kern_polling, OID_AUTO, burst, CTLFLAG_RD,
107 &poll_burst, 0, "Current polling burst size");
108
109 static int netisr_poll_scheduled;
110 static int netisr_pollmore_scheduled;
111 static int poll_shutting_down;
112
poll_burst_max_sysctl(SYSCTL_HANDLER_ARGS)113 static int poll_burst_max_sysctl(SYSCTL_HANDLER_ARGS)
114 {
115 uint32_t val = poll_burst_max;
116 int error;
117
118 error = sysctl_handle_int(oidp, &val, 0, req);
119 if (error || !req->newptr )
120 return (error);
121 if (val < MIN_POLL_BURST_MAX || val > MAX_POLL_BURST_MAX)
122 return (EINVAL);
123
124 mtx_lock(&poll_mtx);
125 poll_burst_max = val;
126 if (poll_burst > poll_burst_max)
127 poll_burst = poll_burst_max;
128 if (poll_each_burst > poll_burst_max)
129 poll_each_burst = MIN_POLL_BURST_MAX;
130 mtx_unlock(&poll_mtx);
131
132 return (0);
133 }
134 SYSCTL_PROC(_kern_polling, OID_AUTO, burst_max,
135 CTLTYPE_UINT | CTLFLAG_RW | CTLFLAG_MPSAFE, 0, sizeof(uint32_t),
136 poll_burst_max_sysctl, "I",
137 "Max Polling burst size");
138
poll_each_burst_sysctl(SYSCTL_HANDLER_ARGS)139 static int poll_each_burst_sysctl(SYSCTL_HANDLER_ARGS)
140 {
141 uint32_t val = poll_each_burst;
142 int error;
143
144 error = sysctl_handle_int(oidp, &val, 0, req);
145 if (error || !req->newptr )
146 return (error);
147 if (val < 1)
148 return (EINVAL);
149
150 mtx_lock(&poll_mtx);
151 if (val > poll_burst_max) {
152 mtx_unlock(&poll_mtx);
153 return (EINVAL);
154 }
155 poll_each_burst = val;
156 mtx_unlock(&poll_mtx);
157
158 return (0);
159 }
160 SYSCTL_PROC(_kern_polling, OID_AUTO, each_burst,
161 CTLTYPE_UINT | CTLFLAG_RW | CTLFLAG_MPSAFE, 0, sizeof(uint32_t),
162 poll_each_burst_sysctl, "I",
163 "Max size of each burst");
164
165 static uint32_t poll_in_idle_loop=0; /* do we poll in idle loop ? */
166 SYSCTL_UINT(_kern_polling, OID_AUTO, idle_poll, CTLFLAG_RW,
167 &poll_in_idle_loop, 0, "Enable device polling in idle loop");
168
169 static uint32_t user_frac = 50;
user_frac_sysctl(SYSCTL_HANDLER_ARGS)170 static int user_frac_sysctl(SYSCTL_HANDLER_ARGS)
171 {
172 uint32_t val = user_frac;
173 int error;
174
175 error = sysctl_handle_int(oidp, &val, 0, req);
176 if (error || !req->newptr )
177 return (error);
178 if (val > 99)
179 return (EINVAL);
180
181 mtx_lock(&poll_mtx);
182 user_frac = val;
183 mtx_unlock(&poll_mtx);
184
185 return (0);
186 }
187 SYSCTL_PROC(_kern_polling, OID_AUTO, user_frac,
188 CTLTYPE_UINT | CTLFLAG_RW | CTLFLAG_MPSAFE, 0, sizeof(uint32_t),
189 user_frac_sysctl, "I",
190 "Desired user fraction of cpu time");
191
192 static uint32_t reg_frac_count = 0;
193 static uint32_t reg_frac = 20 ;
reg_frac_sysctl(SYSCTL_HANDLER_ARGS)194 static int reg_frac_sysctl(SYSCTL_HANDLER_ARGS)
195 {
196 uint32_t val = reg_frac;
197 int error;
198
199 error = sysctl_handle_int(oidp, &val, 0, req);
200 if (error || !req->newptr )
201 return (error);
202 if (val < 1 || val > hz)
203 return (EINVAL);
204
205 mtx_lock(&poll_mtx);
206 reg_frac = val;
207 if (reg_frac_count >= reg_frac)
208 reg_frac_count = 0;
209 mtx_unlock(&poll_mtx);
210
211 return (0);
212 }
213 SYSCTL_PROC(_kern_polling, OID_AUTO, reg_frac,
214 CTLTYPE_UINT | CTLFLAG_RW | CTLFLAG_MPSAFE, 0, sizeof(uint32_t),
215 reg_frac_sysctl, "I",
216 "Every this many cycles check registers");
217
218 static uint32_t short_ticks;
219 SYSCTL_UINT(_kern_polling, OID_AUTO, short_ticks, CTLFLAG_RD,
220 &short_ticks, 0, "Hardclock ticks shorter than they should be");
221
222 static uint32_t lost_polls;
223 SYSCTL_UINT(_kern_polling, OID_AUTO, lost_polls, CTLFLAG_RD,
224 &lost_polls, 0, "How many times we would have lost a poll tick");
225
226 static uint32_t pending_polls;
227 SYSCTL_UINT(_kern_polling, OID_AUTO, pending_polls, CTLFLAG_RD,
228 &pending_polls, 0, "Do we need to poll again");
229
230 static int residual_burst = 0;
231 SYSCTL_INT(_kern_polling, OID_AUTO, residual_burst, CTLFLAG_RD,
232 &residual_burst, 0, "# of residual cycles in burst");
233
234 static uint32_t poll_handlers; /* next free entry in pr[]. */
235 SYSCTL_UINT(_kern_polling, OID_AUTO, handlers, CTLFLAG_RD,
236 &poll_handlers, 0, "Number of registered poll handlers");
237
238 static uint32_t phase;
239 SYSCTL_UINT(_kern_polling, OID_AUTO, phase, CTLFLAG_RD,
240 &phase, 0, "Polling phase");
241
242 static uint32_t suspect;
243 SYSCTL_UINT(_kern_polling, OID_AUTO, suspect, CTLFLAG_RD,
244 &suspect, 0, "suspect event");
245
246 static uint32_t stalled;
247 SYSCTL_UINT(_kern_polling, OID_AUTO, stalled, CTLFLAG_RD,
248 &stalled, 0, "potential stalls");
249
250 static uint32_t idlepoll_sleeping; /* idlepoll is sleeping */
251 SYSCTL_UINT(_kern_polling, OID_AUTO, idlepoll_sleeping, CTLFLAG_RD,
252 &idlepoll_sleeping, 0, "idlepoll is sleeping");
253
254 #define POLL_LIST_LEN 128
255 struct pollrec {
256 poll_handler_t *handler;
257 struct ifnet *ifp;
258 };
259
260 static struct pollrec pr[POLL_LIST_LEN];
261
262 static void
poll_shutdown(void * arg,int howto)263 poll_shutdown(void *arg, int howto)
264 {
265
266 poll_shutting_down = 1;
267 }
268
269 static void
init_device_poll(void)270 init_device_poll(void)
271 {
272
273 mtx_init(&poll_mtx, "polling", NULL, MTX_DEF);
274 EVENTHANDLER_REGISTER(shutdown_post_sync, poll_shutdown, NULL,
275 SHUTDOWN_PRI_LAST);
276 }
277 SYSINIT(device_poll, SI_SUB_SOFTINTR, SI_ORDER_MIDDLE, init_device_poll, NULL);
278
279 /*
280 * Hook from hardclock. Tries to schedule a netisr, but keeps track
281 * of lost ticks due to the previous handler taking too long.
282 * Normally, this should not happen, because polling handler should
283 * run for a short time. However, in some cases (e.g. when there are
284 * changes in link status etc.) the drivers take a very long time
285 * (even in the order of milliseconds) to reset and reconfigure the
286 * device, causing apparent lost polls.
287 *
288 * The first part of the code is just for debugging purposes, and tries
289 * to count how often hardclock ticks are shorter than they should,
290 * meaning either stray interrupts or delayed events.
291 */
292 void
hardclock_device_poll(void)293 hardclock_device_poll(void)
294 {
295 static struct timeval prev_t, t;
296 int delta;
297
298 if (poll_handlers == 0 || poll_shutting_down)
299 return;
300
301 microuptime(&t);
302 delta = (t.tv_usec - prev_t.tv_usec) +
303 (t.tv_sec - prev_t.tv_sec)*1000000;
304 if (delta * hz < 500000)
305 short_ticks++;
306 else
307 prev_t = t;
308
309 if (pending_polls > 100) {
310 /*
311 * Too much, assume it has stalled (not always true
312 * see comment above).
313 */
314 stalled++;
315 pending_polls = 0;
316 phase = 0;
317 }
318
319 if (phase <= 2) {
320 if (phase != 0)
321 suspect++;
322 phase = 1;
323 netisr_poll_scheduled = 1;
324 netisr_pollmore_scheduled = 1;
325 netisr_sched_poll();
326 phase = 2;
327 }
328 if (pending_polls++ > 0)
329 lost_polls++;
330 }
331
332 /*
333 * ether_poll is called from the idle loop.
334 */
335 static void
ether_poll(int count)336 ether_poll(int count)
337 {
338 struct epoch_tracker et;
339 int i;
340
341 mtx_lock(&poll_mtx);
342
343 if (count > poll_each_burst)
344 count = poll_each_burst;
345
346 NET_EPOCH_ENTER(et);
347 for (i = 0 ; i < poll_handlers ; i++)
348 pr[i].handler(pr[i].ifp, POLL_ONLY, count);
349 NET_EPOCH_EXIT(et);
350
351 mtx_unlock(&poll_mtx);
352 }
353
354 /*
355 * netisr_pollmore is called after other netisr's, possibly scheduling
356 * another NETISR_POLL call, or adapting the burst size for the next cycle.
357 *
358 * It is very bad to fetch large bursts of packets from a single card at once,
359 * because the burst could take a long time to be completely processed, or
360 * could saturate the intermediate queue (ipintrq or similar) leading to
361 * losses or unfairness. To reduce the problem, and also to account better for
362 * time spent in network-related processing, we split the burst in smaller
363 * chunks of fixed size, giving control to the other netisr's between chunks.
364 * This helps in improving the fairness, reducing livelock (because we
365 * emulate more closely the "process to completion" that we have with
366 * fastforwarding) and accounting for the work performed in low level
367 * handling and forwarding.
368 */
369
370 static struct timeval poll_start_t;
371
372 void
netisr_pollmore(void)373 netisr_pollmore(void)
374 {
375 struct timeval t;
376 int kern_load;
377
378 if (poll_handlers == 0)
379 return;
380
381 mtx_lock(&poll_mtx);
382 if (!netisr_pollmore_scheduled) {
383 mtx_unlock(&poll_mtx);
384 return;
385 }
386 netisr_pollmore_scheduled = 0;
387 phase = 5;
388 if (residual_burst > 0) {
389 netisr_poll_scheduled = 1;
390 netisr_pollmore_scheduled = 1;
391 netisr_sched_poll();
392 mtx_unlock(&poll_mtx);
393 /* will run immediately on return, followed by netisrs */
394 return;
395 }
396 /* here we can account time spent in netisr's in this tick */
397 microuptime(&t);
398 kern_load = (t.tv_usec - poll_start_t.tv_usec) +
399 (t.tv_sec - poll_start_t.tv_sec)*1000000; /* us */
400 kern_load = (kern_load * hz) / 10000; /* 0..100 */
401 if (kern_load > (100 - user_frac)) { /* try decrease ticks */
402 if (poll_burst > 1)
403 poll_burst--;
404 } else {
405 if (poll_burst < poll_burst_max)
406 poll_burst++;
407 }
408
409 pending_polls--;
410 if (pending_polls == 0) /* we are done */
411 phase = 0;
412 else {
413 /*
414 * Last cycle was long and caused us to miss one or more
415 * hardclock ticks. Restart processing again, but slightly
416 * reduce the burst size to prevent that this happens again.
417 */
418 poll_burst -= (poll_burst / 8);
419 if (poll_burst < 1)
420 poll_burst = 1;
421 netisr_poll_scheduled = 1;
422 netisr_pollmore_scheduled = 1;
423 netisr_sched_poll();
424 phase = 6;
425 }
426 mtx_unlock(&poll_mtx);
427 }
428
429 /*
430 * netisr_poll is typically scheduled once per tick.
431 */
432 void
netisr_poll(void)433 netisr_poll(void)
434 {
435 int i, cycles;
436 enum poll_cmd arg = POLL_ONLY;
437
438 NET_EPOCH_ASSERT();
439
440 if (poll_handlers == 0)
441 return;
442
443 mtx_lock(&poll_mtx);
444 if (!netisr_poll_scheduled) {
445 mtx_unlock(&poll_mtx);
446 return;
447 }
448 netisr_poll_scheduled = 0;
449 phase = 3;
450 if (residual_burst == 0) { /* first call in this tick */
451 microuptime(&poll_start_t);
452 if (++reg_frac_count == reg_frac) {
453 arg = POLL_AND_CHECK_STATUS;
454 reg_frac_count = 0;
455 }
456
457 residual_burst = poll_burst;
458 }
459 cycles = (residual_burst < poll_each_burst) ?
460 residual_burst : poll_each_burst;
461 residual_burst -= cycles;
462
463 for (i = 0 ; i < poll_handlers ; i++)
464 pr[i].handler(pr[i].ifp, arg, cycles);
465
466 phase = 4;
467 mtx_unlock(&poll_mtx);
468 }
469
470 /*
471 * Try to register routine for polling. Returns 0 if successful
472 * (and polling should be enabled), error code otherwise.
473 * A device is not supposed to register itself multiple times.
474 *
475 * This is called from within the *_ioctl() functions.
476 */
477 int
ether_poll_register(poll_handler_t * h,if_t ifp)478 ether_poll_register(poll_handler_t *h, if_t ifp)
479 {
480 int i;
481
482 KASSERT(h != NULL, ("%s: handler is NULL", __func__));
483 KASSERT(ifp != NULL, ("%s: ifp is NULL", __func__));
484
485 mtx_lock(&poll_mtx);
486 if (poll_handlers >= POLL_LIST_LEN) {
487 /*
488 * List full, cannot register more entries.
489 * This should never happen; if it does, it is probably a
490 * broken driver trying to register multiple times. Checking
491 * this at runtime is expensive, and won't solve the problem
492 * anyways, so just report a few times and then give up.
493 */
494 static int verbose = 10 ;
495 if (verbose >0) {
496 log(LOG_ERR, "poll handlers list full, "
497 "maybe a broken driver ?\n");
498 verbose--;
499 }
500 mtx_unlock(&poll_mtx);
501 return (ENOMEM); /* no polling for you */
502 }
503
504 for (i = 0 ; i < poll_handlers ; i++)
505 if (pr[i].ifp == ifp && pr[i].handler != NULL) {
506 mtx_unlock(&poll_mtx);
507 log(LOG_DEBUG, "ether_poll_register: %s: handler"
508 " already registered\n", if_name(ifp));
509 return (EEXIST);
510 }
511
512 pr[poll_handlers].handler = h;
513 pr[poll_handlers].ifp = ifp;
514 poll_handlers++;
515 mtx_unlock(&poll_mtx);
516 if (idlepoll_sleeping)
517 wakeup(&idlepoll_sleeping);
518 return (0);
519 }
520
521 /*
522 * Remove interface from the polling list. Called from *_ioctl(), too.
523 */
524 int
ether_poll_deregister(if_t ifp)525 ether_poll_deregister(if_t ifp)
526 {
527 int i;
528
529 KASSERT(ifp != NULL, ("%s: ifp is NULL", __func__));
530
531 mtx_lock(&poll_mtx);
532
533 for (i = 0 ; i < poll_handlers ; i++)
534 if (pr[i].ifp == ifp) /* found it */
535 break;
536 if (i == poll_handlers) {
537 log(LOG_DEBUG, "ether_poll_deregister: %s: not found!\n",
538 if_name(ifp));
539 mtx_unlock(&poll_mtx);
540 return (ENOENT);
541 }
542 poll_handlers--;
543 if (i < poll_handlers) { /* Last entry replaces this one. */
544 pr[i].handler = pr[poll_handlers].handler;
545 pr[i].ifp = pr[poll_handlers].ifp;
546 }
547 mtx_unlock(&poll_mtx);
548 return (0);
549 }
550
551 static void
poll_idle(void)552 poll_idle(void)
553 {
554 struct thread *td = curthread;
555 struct rtprio rtp;
556
557 rtp.prio = RTP_PRIO_MAX; /* lowest priority */
558 rtp.type = RTP_PRIO_IDLE;
559 PROC_SLOCK(td->td_proc);
560 rtp_to_pri(&rtp, td);
561 PROC_SUNLOCK(td->td_proc);
562
563 for (;;) {
564 if (poll_in_idle_loop && poll_handlers > 0) {
565 idlepoll_sleeping = 0;
566 ether_poll(poll_each_burst);
567 sched_relinquish(td);
568 } else {
569 idlepoll_sleeping = 1;
570 tsleep(&idlepoll_sleeping, 0, "pollid", hz * 3);
571 }
572 }
573 }
574
575 static struct proc *idlepoll;
576 static struct kproc_desc idlepoll_kp = {
577 "idlepoll",
578 poll_idle,
579 &idlepoll
580 };
581 SYSINIT(idlepoll, SI_SUB_KTHREAD_VM, SI_ORDER_ANY, kproc_start,
582 &idlepoll_kp);
583