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/socket.h> /* needed by net/if.h */ 44 #include <sys/sockio.h> 45 #include <sys/sysctl.h> 46 #include <sys/syslog.h> 47 48 #include <net/if.h> 49 #include <net/if_var.h> 50 #include <net/netisr.h> /* for NETISR_POLL */ 51 #include <net/vnet.h> 52 53 void hardclock_device_poll(void); /* hook from hardclock */ 54 55 static struct mtx poll_mtx; 56 57 /* 58 * Polling support for [network] device drivers. 59 * 60 * Drivers which support this feature can register with the 61 * polling code. 62 * 63 * If registration is successful, the driver must disable interrupts, 64 * and further I/O is performed through the handler, which is invoked 65 * (at least once per clock tick) with 3 arguments: the "arg" passed at 66 * register time (a struct ifnet pointer), a command, and a "count" limit. 67 * 68 * The command can be one of the following: 69 * POLL_ONLY: quick move of "count" packets from input/output queues. 70 * POLL_AND_CHECK_STATUS: as above, plus check status registers or do 71 * other more expensive operations. This command is issued periodically 72 * but less frequently than POLL_ONLY. 73 * 74 * The count limit specifies how much work the handler can do during the 75 * call -- typically this is the number of packets to be received, or 76 * transmitted, etc. (drivers are free to interpret this number, as long 77 * as the max time spent in the function grows roughly linearly with the 78 * count). 79 * 80 * Polling is enabled and disabled via setting IFCAP_POLLING flag on 81 * the interface. The driver ioctl handler should register interface 82 * with polling and disable interrupts, if registration was successful. 83 * 84 * A second variable controls the sharing of CPU between polling/kernel 85 * network processing, and other activities (typically userlevel tasks): 86 * kern.polling.user_frac (between 0 and 100, default 50) sets the share 87 * of CPU allocated to user tasks. CPU is allocated proportionally to the 88 * shares, by dynamically adjusting the "count" (poll_burst). 89 * 90 * Other parameters can should be left to their default values. 91 * The following constraints hold 92 * 93 * 1 <= poll_each_burst <= poll_burst <= poll_burst_max 94 * MIN_POLL_BURST_MAX <= poll_burst_max <= MAX_POLL_BURST_MAX 95 */ 96 97 #define MIN_POLL_BURST_MAX 10 98 #define MAX_POLL_BURST_MAX 20000 99 100 static uint32_t poll_burst = 5; 101 static uint32_t poll_burst_max = 150; /* good for 100Mbit net and HZ=1000 */ 102 static uint32_t poll_each_burst = 5; 103 104 static SYSCTL_NODE(_kern, OID_AUTO, polling, CTLFLAG_RW, 0, 105 "Device polling parameters"); 106 107 SYSCTL_UINT(_kern_polling, OID_AUTO, burst, CTLFLAG_RD, 108 &poll_burst, 0, "Current polling burst size"); 109 110 static int netisr_poll_scheduled; 111 static int netisr_pollmore_scheduled; 112 static int poll_shutting_down; 113 114 static int poll_burst_max_sysctl(SYSCTL_HANDLER_ARGS) 115 { 116 uint32_t val = poll_burst_max; 117 int error; 118 119 error = sysctl_handle_int(oidp, &val, 0, req); 120 if (error || !req->newptr ) 121 return (error); 122 if (val < MIN_POLL_BURST_MAX || val > MAX_POLL_BURST_MAX) 123 return (EINVAL); 124 125 mtx_lock(&poll_mtx); 126 poll_burst_max = val; 127 if (poll_burst > poll_burst_max) 128 poll_burst = poll_burst_max; 129 if (poll_each_burst > poll_burst_max) 130 poll_each_burst = MIN_POLL_BURST_MAX; 131 mtx_unlock(&poll_mtx); 132 133 return (0); 134 } 135 SYSCTL_PROC(_kern_polling, OID_AUTO, burst_max, CTLTYPE_UINT | CTLFLAG_RW, 136 0, sizeof(uint32_t), poll_burst_max_sysctl, "I", "Max Polling burst size"); 137 138 static int poll_each_burst_sysctl(SYSCTL_HANDLER_ARGS) 139 { 140 uint32_t val = poll_each_burst; 141 int error; 142 143 error = sysctl_handle_int(oidp, &val, 0, req); 144 if (error || !req->newptr ) 145 return (error); 146 if (val < 1) 147 return (EINVAL); 148 149 mtx_lock(&poll_mtx); 150 if (val > poll_burst_max) { 151 mtx_unlock(&poll_mtx); 152 return (EINVAL); 153 } 154 poll_each_burst = val; 155 mtx_unlock(&poll_mtx); 156 157 return (0); 158 } 159 SYSCTL_PROC(_kern_polling, OID_AUTO, each_burst, CTLTYPE_UINT | CTLFLAG_RW, 160 0, sizeof(uint32_t), poll_each_burst_sysctl, "I", 161 "Max size of each burst"); 162 163 static uint32_t poll_in_idle_loop=0; /* do we poll in idle loop ? */ 164 SYSCTL_UINT(_kern_polling, OID_AUTO, idle_poll, CTLFLAG_RW, 165 &poll_in_idle_loop, 0, "Enable device polling in idle loop"); 166 167 static uint32_t user_frac = 50; 168 static int user_frac_sysctl(SYSCTL_HANDLER_ARGS) 169 { 170 uint32_t val = user_frac; 171 int error; 172 173 error = sysctl_handle_int(oidp, &val, 0, req); 174 if (error || !req->newptr ) 175 return (error); 176 if (val > 99) 177 return (EINVAL); 178 179 mtx_lock(&poll_mtx); 180 user_frac = val; 181 mtx_unlock(&poll_mtx); 182 183 return (0); 184 } 185 SYSCTL_PROC(_kern_polling, OID_AUTO, user_frac, CTLTYPE_UINT | CTLFLAG_RW, 186 0, sizeof(uint32_t), user_frac_sysctl, "I", 187 "Desired user fraction of cpu time"); 188 189 static uint32_t reg_frac_count = 0; 190 static uint32_t reg_frac = 20 ; 191 static int reg_frac_sysctl(SYSCTL_HANDLER_ARGS) 192 { 193 uint32_t val = reg_frac; 194 int error; 195 196 error = sysctl_handle_int(oidp, &val, 0, req); 197 if (error || !req->newptr ) 198 return (error); 199 if (val < 1 || val > hz) 200 return (EINVAL); 201 202 mtx_lock(&poll_mtx); 203 reg_frac = val; 204 if (reg_frac_count >= reg_frac) 205 reg_frac_count = 0; 206 mtx_unlock(&poll_mtx); 207 208 return (0); 209 } 210 SYSCTL_PROC(_kern_polling, OID_AUTO, reg_frac, CTLTYPE_UINT | CTLFLAG_RW, 211 0, sizeof(uint32_t), reg_frac_sysctl, "I", 212 "Every this many cycles check registers"); 213 214 static uint32_t short_ticks; 215 SYSCTL_UINT(_kern_polling, OID_AUTO, short_ticks, CTLFLAG_RD, 216 &short_ticks, 0, "Hardclock ticks shorter than they should be"); 217 218 static uint32_t lost_polls; 219 SYSCTL_UINT(_kern_polling, OID_AUTO, lost_polls, CTLFLAG_RD, 220 &lost_polls, 0, "How many times we would have lost a poll tick"); 221 222 static uint32_t pending_polls; 223 SYSCTL_UINT(_kern_polling, OID_AUTO, pending_polls, CTLFLAG_RD, 224 &pending_polls, 0, "Do we need to poll again"); 225 226 static int residual_burst = 0; 227 SYSCTL_INT(_kern_polling, OID_AUTO, residual_burst, CTLFLAG_RD, 228 &residual_burst, 0, "# of residual cycles in burst"); 229 230 static uint32_t poll_handlers; /* next free entry in pr[]. */ 231 SYSCTL_UINT(_kern_polling, OID_AUTO, handlers, CTLFLAG_RD, 232 &poll_handlers, 0, "Number of registered poll handlers"); 233 234 static uint32_t phase; 235 SYSCTL_UINT(_kern_polling, OID_AUTO, phase, CTLFLAG_RD, 236 &phase, 0, "Polling phase"); 237 238 static uint32_t suspect; 239 SYSCTL_UINT(_kern_polling, OID_AUTO, suspect, CTLFLAG_RD, 240 &suspect, 0, "suspect event"); 241 242 static uint32_t stalled; 243 SYSCTL_UINT(_kern_polling, OID_AUTO, stalled, CTLFLAG_RD, 244 &stalled, 0, "potential stalls"); 245 246 static uint32_t idlepoll_sleeping; /* idlepoll is sleeping */ 247 SYSCTL_UINT(_kern_polling, OID_AUTO, idlepoll_sleeping, CTLFLAG_RD, 248 &idlepoll_sleeping, 0, "idlepoll is sleeping"); 249 250 251 #define POLL_LIST_LEN 128 252 struct pollrec { 253 poll_handler_t *handler; 254 struct ifnet *ifp; 255 }; 256 257 static struct pollrec pr[POLL_LIST_LEN]; 258 259 static void 260 poll_shutdown(void *arg, int howto) 261 { 262 263 poll_shutting_down = 1; 264 } 265 266 static void 267 init_device_poll(void) 268 { 269 270 mtx_init(&poll_mtx, "polling", NULL, MTX_DEF); 271 EVENTHANDLER_REGISTER(shutdown_post_sync, poll_shutdown, NULL, 272 SHUTDOWN_PRI_LAST); 273 } 274 SYSINIT(device_poll, SI_SUB_SOFTINTR, SI_ORDER_MIDDLE, init_device_poll, NULL); 275 276 277 /* 278 * Hook from hardclock. Tries to schedule a netisr, but keeps track 279 * of lost ticks due to the previous handler taking too long. 280 * Normally, this should not happen, because polling handler should 281 * run for a short time. However, in some cases (e.g. when there are 282 * changes in link status etc.) the drivers take a very long time 283 * (even in the order of milliseconds) to reset and reconfigure the 284 * device, causing apparent lost polls. 285 * 286 * The first part of the code is just for debugging purposes, and tries 287 * to count how often hardclock ticks are shorter than they should, 288 * meaning either stray interrupts or delayed events. 289 */ 290 void 291 hardclock_device_poll(void) 292 { 293 static struct timeval prev_t, t; 294 int delta; 295 296 if (poll_handlers == 0 || poll_shutting_down) 297 return; 298 299 microuptime(&t); 300 delta = (t.tv_usec - prev_t.tv_usec) + 301 (t.tv_sec - prev_t.tv_sec)*1000000; 302 if (delta * hz < 500000) 303 short_ticks++; 304 else 305 prev_t = t; 306 307 if (pending_polls > 100) { 308 /* 309 * Too much, assume it has stalled (not always true 310 * see comment above). 311 */ 312 stalled++; 313 pending_polls = 0; 314 phase = 0; 315 } 316 317 if (phase <= 2) { 318 if (phase != 0) 319 suspect++; 320 phase = 1; 321 netisr_poll_scheduled = 1; 322 netisr_pollmore_scheduled = 1; 323 netisr_sched_poll(); 324 phase = 2; 325 } 326 if (pending_polls++ > 0) 327 lost_polls++; 328 } 329 330 /* 331 * ether_poll is called from the idle loop. 332 */ 333 static void 334 ether_poll(int count) 335 { 336 struct epoch_tracker et; 337 int i; 338 339 mtx_lock(&poll_mtx); 340 341 if (count > poll_each_burst) 342 count = poll_each_burst; 343 344 NET_EPOCH_ENTER(et); 345 for (i = 0 ; i < poll_handlers ; i++) 346 pr[i].handler(pr[i].ifp, POLL_ONLY, count); 347 NET_EPOCH_EXIT(et); 348 349 mtx_unlock(&poll_mtx); 350 } 351 352 /* 353 * netisr_pollmore is called after other netisr's, possibly scheduling 354 * another NETISR_POLL call, or adapting the burst size for the next cycle. 355 * 356 * It is very bad to fetch large bursts of packets from a single card at once, 357 * because the burst could take a long time to be completely processed, or 358 * could saturate the intermediate queue (ipintrq or similar) leading to 359 * losses or unfairness. To reduce the problem, and also to account better for 360 * time spent in network-related processing, we split the burst in smaller 361 * chunks of fixed size, giving control to the other netisr's between chunks. 362 * This helps in improving the fairness, reducing livelock (because we 363 * emulate more closely the "process to completion" that we have with 364 * fastforwarding) and accounting for the work performed in low level 365 * handling and forwarding. 366 */ 367 368 static struct timeval poll_start_t; 369 370 void 371 netisr_pollmore() 372 { 373 struct timeval t; 374 int kern_load; 375 376 if (poll_handlers == 0) 377 return; 378 379 mtx_lock(&poll_mtx); 380 if (!netisr_pollmore_scheduled) { 381 mtx_unlock(&poll_mtx); 382 return; 383 } 384 netisr_pollmore_scheduled = 0; 385 phase = 5; 386 if (residual_burst > 0) { 387 netisr_poll_scheduled = 1; 388 netisr_pollmore_scheduled = 1; 389 netisr_sched_poll(); 390 mtx_unlock(&poll_mtx); 391 /* will run immediately on return, followed by netisrs */ 392 return; 393 } 394 /* here we can account time spent in netisr's in this tick */ 395 microuptime(&t); 396 kern_load = (t.tv_usec - poll_start_t.tv_usec) + 397 (t.tv_sec - poll_start_t.tv_sec)*1000000; /* us */ 398 kern_load = (kern_load * hz) / 10000; /* 0..100 */ 399 if (kern_load > (100 - user_frac)) { /* try decrease ticks */ 400 if (poll_burst > 1) 401 poll_burst--; 402 } else { 403 if (poll_burst < poll_burst_max) 404 poll_burst++; 405 } 406 407 pending_polls--; 408 if (pending_polls == 0) /* we are done */ 409 phase = 0; 410 else { 411 /* 412 * Last cycle was long and caused us to miss one or more 413 * hardclock ticks. Restart processing again, but slightly 414 * reduce the burst size to prevent that this happens again. 415 */ 416 poll_burst -= (poll_burst / 8); 417 if (poll_burst < 1) 418 poll_burst = 1; 419 netisr_poll_scheduled = 1; 420 netisr_pollmore_scheduled = 1; 421 netisr_sched_poll(); 422 phase = 6; 423 } 424 mtx_unlock(&poll_mtx); 425 } 426 427 /* 428 * netisr_poll is typically scheduled once per tick. 429 */ 430 void 431 netisr_poll(void) 432 { 433 int i, cycles; 434 enum poll_cmd arg = POLL_ONLY; 435 436 NET_EPOCH_ASSERT(); 437 438 if (poll_handlers == 0) 439 return; 440 441 mtx_lock(&poll_mtx); 442 if (!netisr_poll_scheduled) { 443 mtx_unlock(&poll_mtx); 444 return; 445 } 446 netisr_poll_scheduled = 0; 447 phase = 3; 448 if (residual_burst == 0) { /* first call in this tick */ 449 microuptime(&poll_start_t); 450 if (++reg_frac_count == reg_frac) { 451 arg = POLL_AND_CHECK_STATUS; 452 reg_frac_count = 0; 453 } 454 455 residual_burst = poll_burst; 456 } 457 cycles = (residual_burst < poll_each_burst) ? 458 residual_burst : poll_each_burst; 459 residual_burst -= cycles; 460 461 for (i = 0 ; i < poll_handlers ; i++) 462 pr[i].handler(pr[i].ifp, arg, cycles); 463 464 phase = 4; 465 mtx_unlock(&poll_mtx); 466 } 467 468 /* 469 * Try to register routine for polling. Returns 0 if successful 470 * (and polling should be enabled), error code otherwise. 471 * A device is not supposed to register itself multiple times. 472 * 473 * This is called from within the *_ioctl() functions. 474 */ 475 int 476 ether_poll_register(poll_handler_t *h, if_t ifp) 477 { 478 int i; 479 480 KASSERT(h != NULL, ("%s: handler is NULL", __func__)); 481 KASSERT(ifp != NULL, ("%s: ifp is NULL", __func__)); 482 483 mtx_lock(&poll_mtx); 484 if (poll_handlers >= POLL_LIST_LEN) { 485 /* 486 * List full, cannot register more entries. 487 * This should never happen; if it does, it is probably a 488 * broken driver trying to register multiple times. Checking 489 * this at runtime is expensive, and won't solve the problem 490 * anyways, so just report a few times and then give up. 491 */ 492 static int verbose = 10 ; 493 if (verbose >0) { 494 log(LOG_ERR, "poll handlers list full, " 495 "maybe a broken driver ?\n"); 496 verbose--; 497 } 498 mtx_unlock(&poll_mtx); 499 return (ENOMEM); /* no polling for you */ 500 } 501 502 for (i = 0 ; i < poll_handlers ; i++) 503 if (pr[i].ifp == ifp && pr[i].handler != NULL) { 504 mtx_unlock(&poll_mtx); 505 log(LOG_DEBUG, "ether_poll_register: %s: handler" 506 " already registered\n", ifp->if_xname); 507 return (EEXIST); 508 } 509 510 pr[poll_handlers].handler = h; 511 pr[poll_handlers].ifp = ifp; 512 poll_handlers++; 513 mtx_unlock(&poll_mtx); 514 if (idlepoll_sleeping) 515 wakeup(&idlepoll_sleeping); 516 return (0); 517 } 518 519 /* 520 * Remove interface from the polling list. Called from *_ioctl(), too. 521 */ 522 int 523 ether_poll_deregister(if_t ifp) 524 { 525 int i; 526 527 KASSERT(ifp != NULL, ("%s: ifp is NULL", __func__)); 528 529 mtx_lock(&poll_mtx); 530 531 for (i = 0 ; i < poll_handlers ; i++) 532 if (pr[i].ifp == ifp) /* found it */ 533 break; 534 if (i == poll_handlers) { 535 log(LOG_DEBUG, "ether_poll_deregister: %s: not found!\n", 536 ifp->if_xname); 537 mtx_unlock(&poll_mtx); 538 return (ENOENT); 539 } 540 poll_handlers--; 541 if (i < poll_handlers) { /* Last entry replaces this one. */ 542 pr[i].handler = pr[poll_handlers].handler; 543 pr[i].ifp = pr[poll_handlers].ifp; 544 } 545 mtx_unlock(&poll_mtx); 546 return (0); 547 } 548 549 static void 550 poll_idle(void) 551 { 552 struct thread *td = curthread; 553 struct rtprio rtp; 554 555 rtp.prio = RTP_PRIO_MAX; /* lowest priority */ 556 rtp.type = RTP_PRIO_IDLE; 557 PROC_SLOCK(td->td_proc); 558 rtp_to_pri(&rtp, td); 559 PROC_SUNLOCK(td->td_proc); 560 561 for (;;) { 562 if (poll_in_idle_loop && poll_handlers > 0) { 563 idlepoll_sleeping = 0; 564 ether_poll(poll_each_burst); 565 thread_lock(td); 566 mi_switch(SW_VOL); 567 } else { 568 idlepoll_sleeping = 1; 569 tsleep(&idlepoll_sleeping, 0, "pollid", hz * 3); 570 } 571 } 572 } 573 574 static struct proc *idlepoll; 575 static struct kproc_desc idlepoll_kp = { 576 "idlepoll", 577 poll_idle, 578 &idlepoll 579 }; 580 SYSINIT(idlepoll, SI_SUB_KTHREAD_VM, SI_ORDER_ANY, kproc_start, 581 &idlepoll_kp); 582