1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD 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 __FBSDID("$FreeBSD$"); 32 33 #include "opt_device_polling.h" 34 35 #include <sys/param.h> 36 #include <sys/systm.h> 37 #include <sys/kernel.h> 38 #include <sys/kthread.h> 39 #include <sys/proc.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> 48 49 #include <net/if.h> 50 #include <net/if_var.h> 51 #include <net/netisr.h> /* for NETISR_POLL */ 52 #include <net/vnet.h> 53 54 void hardclock_device_poll(void); /* hook from hardclock */ 55 56 static struct mtx poll_mtx; 57 58 /* 59 * Polling support for [network] device drivers. 60 * 61 * Drivers which support this feature can register with the 62 * polling code. 63 * 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. 68 * 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. 74 * 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 79 * count). 80 * 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. 84 * 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). 90 * 91 * Other parameters can should be left to their default values. 92 * The following constraints hold 93 * 94 * 1 <= poll_each_burst <= poll_burst <= poll_burst_max 95 * MIN_POLL_BURST_MAX <= poll_burst_max <= MAX_POLL_BURST_MAX 96 */ 97 98 #define MIN_POLL_BURST_MAX 10 99 #define MAX_POLL_BURST_MAX 20000 100 101 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; 104 105 static SYSCTL_NODE(_kern, OID_AUTO, polling, CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 106 "Device polling parameters"); 107 108 SYSCTL_UINT(_kern_polling, OID_AUTO, burst, CTLFLAG_RD, 109 &poll_burst, 0, "Current polling burst size"); 110 111 static int netisr_poll_scheduled; 112 static int netisr_pollmore_scheduled; 113 static int poll_shutting_down; 114 115 static int poll_burst_max_sysctl(SYSCTL_HANDLER_ARGS) 116 { 117 uint32_t val = poll_burst_max; 118 int error; 119 120 error = sysctl_handle_int(oidp, &val, 0, req); 121 if (error || !req->newptr ) 122 return (error); 123 if (val < MIN_POLL_BURST_MAX || val > MAX_POLL_BURST_MAX) 124 return (EINVAL); 125 126 mtx_lock(&poll_mtx); 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); 133 134 return (0); 135 } 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"); 140 141 static int poll_each_burst_sysctl(SYSCTL_HANDLER_ARGS) 142 { 143 uint32_t val = poll_each_burst; 144 int error; 145 146 error = sysctl_handle_int(oidp, &val, 0, req); 147 if (error || !req->newptr ) 148 return (error); 149 if (val < 1) 150 return (EINVAL); 151 152 mtx_lock(&poll_mtx); 153 if (val > poll_burst_max) { 154 mtx_unlock(&poll_mtx); 155 return (EINVAL); 156 } 157 poll_each_burst = val; 158 mtx_unlock(&poll_mtx); 159 160 return (0); 161 } 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"); 166 167 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"); 170 171 static uint32_t user_frac = 50; 172 static int user_frac_sysctl(SYSCTL_HANDLER_ARGS) 173 { 174 uint32_t val = user_frac; 175 int error; 176 177 error = sysctl_handle_int(oidp, &val, 0, req); 178 if (error || !req->newptr ) 179 return (error); 180 if (val > 99) 181 return (EINVAL); 182 183 mtx_lock(&poll_mtx); 184 user_frac = val; 185 mtx_unlock(&poll_mtx); 186 187 return (0); 188 } 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"); 193 194 static uint32_t reg_frac_count = 0; 195 static uint32_t reg_frac = 20 ; 196 static int reg_frac_sysctl(SYSCTL_HANDLER_ARGS) 197 { 198 uint32_t val = reg_frac; 199 int error; 200 201 error = sysctl_handle_int(oidp, &val, 0, req); 202 if (error || !req->newptr ) 203 return (error); 204 if (val < 1 || val > hz) 205 return (EINVAL); 206 207 mtx_lock(&poll_mtx); 208 reg_frac = val; 209 if (reg_frac_count >= reg_frac) 210 reg_frac_count = 0; 211 mtx_unlock(&poll_mtx); 212 213 return (0); 214 } 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"); 219 220 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"); 223 224 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"); 227 228 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"); 231 232 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"); 235 236 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"); 239 240 static uint32_t phase; 241 SYSCTL_UINT(_kern_polling, OID_AUTO, phase, CTLFLAG_RD, 242 &phase, 0, "Polling phase"); 243 244 static uint32_t suspect; 245 SYSCTL_UINT(_kern_polling, OID_AUTO, suspect, CTLFLAG_RD, 246 &suspect, 0, "suspect event"); 247 248 static uint32_t stalled; 249 SYSCTL_UINT(_kern_polling, OID_AUTO, stalled, CTLFLAG_RD, 250 &stalled, 0, "potential stalls"); 251 252 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"); 255 256 #define POLL_LIST_LEN 128 257 struct pollrec { 258 poll_handler_t *handler; 259 struct ifnet *ifp; 260 }; 261 262 static struct pollrec pr[POLL_LIST_LEN]; 263 264 static void 265 poll_shutdown(void *arg, int howto) 266 { 267 268 poll_shutting_down = 1; 269 } 270 271 static void 272 init_device_poll(void) 273 { 274 275 mtx_init(&poll_mtx, "polling", NULL, MTX_DEF); 276 EVENTHANDLER_REGISTER(shutdown_post_sync, poll_shutdown, NULL, 277 SHUTDOWN_PRI_LAST); 278 } 279 SYSINIT(device_poll, SI_SUB_SOFTINTR, SI_ORDER_MIDDLE, init_device_poll, NULL); 280 281 /* 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. 289 * 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. 293 */ 294 void 295 hardclock_device_poll(void) 296 { 297 static struct timeval prev_t, t; 298 int delta; 299 300 if (poll_handlers == 0 || poll_shutting_down) 301 return; 302 303 microuptime(&t); 304 delta = (t.tv_usec - prev_t.tv_usec) + 305 (t.tv_sec - prev_t.tv_sec)*1000000; 306 if (delta * hz < 500000) 307 short_ticks++; 308 else 309 prev_t = t; 310 311 if (pending_polls > 100) { 312 /* 313 * Too much, assume it has stalled (not always true 314 * see comment above). 315 */ 316 stalled++; 317 pending_polls = 0; 318 phase = 0; 319 } 320 321 if (phase <= 2) { 322 if (phase != 0) 323 suspect++; 324 phase = 1; 325 netisr_poll_scheduled = 1; 326 netisr_pollmore_scheduled = 1; 327 netisr_sched_poll(); 328 phase = 2; 329 } 330 if (pending_polls++ > 0) 331 lost_polls++; 332 } 333 334 /* 335 * ether_poll is called from the idle loop. 336 */ 337 static void 338 ether_poll(int count) 339 { 340 struct epoch_tracker et; 341 int i; 342 343 mtx_lock(&poll_mtx); 344 345 if (count > poll_each_burst) 346 count = poll_each_burst; 347 348 NET_EPOCH_ENTER(et); 349 for (i = 0 ; i < poll_handlers ; i++) 350 pr[i].handler(pr[i].ifp, POLL_ONLY, count); 351 NET_EPOCH_EXIT(et); 352 353 mtx_unlock(&poll_mtx); 354 } 355 356 /* 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. 359 * 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. 370 */ 371 372 static struct timeval poll_start_t; 373 374 void 375 netisr_pollmore(void) 376 { 377 struct timeval t; 378 int kern_load; 379 380 if (poll_handlers == 0) 381 return; 382 383 mtx_lock(&poll_mtx); 384 if (!netisr_pollmore_scheduled) { 385 mtx_unlock(&poll_mtx); 386 return; 387 } 388 netisr_pollmore_scheduled = 0; 389 phase = 5; 390 if (residual_burst > 0) { 391 netisr_poll_scheduled = 1; 392 netisr_pollmore_scheduled = 1; 393 netisr_sched_poll(); 394 mtx_unlock(&poll_mtx); 395 /* will run immediately on return, followed by netisrs */ 396 return; 397 } 398 /* here we can account time spent in netisr's in this tick */ 399 microuptime(&t); 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 */ 404 if (poll_burst > 1) 405 poll_burst--; 406 } else { 407 if (poll_burst < poll_burst_max) 408 poll_burst++; 409 } 410 411 pending_polls--; 412 if (pending_polls == 0) /* we are done */ 413 phase = 0; 414 else { 415 /* 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. 419 */ 420 poll_burst -= (poll_burst / 8); 421 if (poll_burst < 1) 422 poll_burst = 1; 423 netisr_poll_scheduled = 1; 424 netisr_pollmore_scheduled = 1; 425 netisr_sched_poll(); 426 phase = 6; 427 } 428 mtx_unlock(&poll_mtx); 429 } 430 431 /* 432 * netisr_poll is typically scheduled once per tick. 433 */ 434 void 435 netisr_poll(void) 436 { 437 int i, cycles; 438 enum poll_cmd arg = POLL_ONLY; 439 440 NET_EPOCH_ASSERT(); 441 442 if (poll_handlers == 0) 443 return; 444 445 mtx_lock(&poll_mtx); 446 if (!netisr_poll_scheduled) { 447 mtx_unlock(&poll_mtx); 448 return; 449 } 450 netisr_poll_scheduled = 0; 451 phase = 3; 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; 456 reg_frac_count = 0; 457 } 458 459 residual_burst = poll_burst; 460 } 461 cycles = (residual_burst < poll_each_burst) ? 462 residual_burst : poll_each_burst; 463 residual_burst -= cycles; 464 465 for (i = 0 ; i < poll_handlers ; i++) 466 pr[i].handler(pr[i].ifp, arg, cycles); 467 468 phase = 4; 469 mtx_unlock(&poll_mtx); 470 } 471 472 /* 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. 476 * 477 * This is called from within the *_ioctl() functions. 478 */ 479 int 480 ether_poll_register(poll_handler_t *h, if_t ifp) 481 { 482 int i; 483 484 KASSERT(h != NULL, ("%s: handler is NULL", __func__)); 485 KASSERT(ifp != NULL, ("%s: ifp is NULL", __func__)); 486 487 mtx_lock(&poll_mtx); 488 if (poll_handlers >= POLL_LIST_LEN) { 489 /* 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. 495 */ 496 static int verbose = 10 ; 497 if (verbose >0) { 498 log(LOG_ERR, "poll handlers list full, " 499 "maybe a broken driver ?\n"); 500 verbose--; 501 } 502 mtx_unlock(&poll_mtx); 503 return (ENOMEM); /* no polling for you */ 504 } 505 506 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)); 511 return (EEXIST); 512 } 513 514 pr[poll_handlers].handler = h; 515 pr[poll_handlers].ifp = ifp; 516 poll_handlers++; 517 mtx_unlock(&poll_mtx); 518 if (idlepoll_sleeping) 519 wakeup(&idlepoll_sleeping); 520 return (0); 521 } 522 523 /* 524 * Remove interface from the polling list. Called from *_ioctl(), too. 525 */ 526 int 527 ether_poll_deregister(if_t ifp) 528 { 529 int i; 530 531 KASSERT(ifp != NULL, ("%s: ifp is NULL", __func__)); 532 533 mtx_lock(&poll_mtx); 534 535 for (i = 0 ; i < poll_handlers ; i++) 536 if (pr[i].ifp == ifp) /* found it */ 537 break; 538 if (i == poll_handlers) { 539 log(LOG_DEBUG, "ether_poll_deregister: %s: not found!\n", 540 if_name(ifp)); 541 mtx_unlock(&poll_mtx); 542 return (ENOENT); 543 } 544 poll_handlers--; 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; 548 } 549 mtx_unlock(&poll_mtx); 550 return (0); 551 } 552 553 static void 554 poll_idle(void) 555 { 556 struct thread *td = curthread; 557 struct rtprio rtp; 558 559 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); 564 565 for (;;) { 566 if (poll_in_idle_loop && poll_handlers > 0) { 567 idlepoll_sleeping = 0; 568 ether_poll(poll_each_burst); 569 sched_relinquish(td); 570 } else { 571 idlepoll_sleeping = 1; 572 tsleep(&idlepoll_sleeping, 0, "pollid", hz * 3); 573 } 574 } 575 } 576 577 static struct proc *idlepoll; 578 static struct kproc_desc idlepoll_kp = { 579 "idlepoll", 580 poll_idle, 581 &idlepoll 582 }; 583 SYSINIT(idlepoll, SI_SUB_KTHREAD_VM, SI_ORDER_ANY, kproc_start, 584 &idlepoll_kp); 585