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