1 /*- 2 * Copyright (c) 2001-2002 Luigi Rizzo 3 * 4 * Supported by: the Xorp Project (www.xorp.org) 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND 16 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 18 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE 19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 25 * SUCH DAMAGE. 26 */ 27 28 #include <sys/cdefs.h> 29 __FBSDID("$FreeBSD$"); 30 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/socket.h> /* needed by net/if.h */ 37 #include <sys/sockio.h> 38 #include <sys/sysctl.h> 39 #include <sys/syslog.h> 40 41 #include <net/if.h> /* for IFF_* flags */ 42 #include <net/netisr.h> /* for NETISR_POLL */ 43 44 #include <sys/proc.h> 45 #include <sys/resourcevar.h> 46 #include <sys/kthread.h> 47 48 static void netisr_poll(void); /* the two netisr handlers */ 49 static void netisr_pollmore(void); 50 static int poll_switch(SYSCTL_HANDLER_ARGS); 51 52 void hardclock_device_poll(void); /* hook from hardclock */ 53 void ether_poll(int); /* polling in idle loop */ 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 * 0 <= poll_each_burst 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 1000 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 SYSCTL_NODE(_kern, OID_AUTO, polling, CTLFLAG_RW, 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 poll_burst_max_sysctl(SYSCTL_HANDLER_ARGS) 112 { 113 uint32_t val = poll_burst_max; 114 int error; 115 116 error = sysctl_handle_int(oidp, &val, 0, req); 117 if (error || !req->newptr ) 118 return (error); 119 if (val < MIN_POLL_BURST_MAX || val > MAX_POLL_BURST_MAX) 120 return (EINVAL); 121 122 mtx_lock(&poll_mtx); 123 poll_burst_max = val; 124 if (poll_burst > poll_burst_max) 125 poll_burst = poll_burst_max; 126 if (poll_each_burst > poll_burst_max) 127 poll_each_burst = MIN_POLL_BURST_MAX; 128 mtx_unlock(&poll_mtx); 129 130 return (0); 131 } 132 SYSCTL_PROC(_kern_polling, OID_AUTO, burst_max, CTLTYPE_UINT | CTLFLAG_RW, 133 0, sizeof(uint32_t), poll_burst_max_sysctl, "I", "Max Polling burst size"); 134 135 static int poll_each_burst_sysctl(SYSCTL_HANDLER_ARGS) 136 { 137 uint32_t val = poll_each_burst; 138 int error; 139 140 error = sysctl_handle_int(oidp, &val, 0, req); 141 if (error || !req->newptr ) 142 return (error); 143 if (val < 1) 144 return (EINVAL); 145 146 mtx_lock(&poll_mtx); 147 if (val > poll_burst_max) { 148 mtx_unlock(&poll_mtx); 149 return (EINVAL); 150 } 151 poll_each_burst = val; 152 mtx_unlock(&poll_mtx); 153 154 return (0); 155 } 156 SYSCTL_PROC(_kern_polling, OID_AUTO, each_burst, CTLTYPE_UINT | CTLFLAG_RW, 157 0, sizeof(uint32_t), poll_each_burst_sysctl, "I", 158 "Max size of each burst"); 159 160 static uint32_t poll_in_idle_loop=0; /* do we poll in idle loop ? */ 161 SYSCTL_UINT(_kern_polling, OID_AUTO, idle_poll, CTLFLAG_RW, 162 &poll_in_idle_loop, 0, "Enable device polling in idle loop"); 163 164 static uint32_t user_frac = 50; 165 static int user_frac_sysctl(SYSCTL_HANDLER_ARGS) 166 { 167 uint32_t val = user_frac; 168 int error; 169 170 error = sysctl_handle_int(oidp, &val, 0, req); 171 if (error || !req->newptr ) 172 return (error); 173 if (val < 0 || val > 99) 174 return (EINVAL); 175 176 mtx_lock(&poll_mtx); 177 user_frac = val; 178 mtx_unlock(&poll_mtx); 179 180 return (0); 181 } 182 SYSCTL_PROC(_kern_polling, OID_AUTO, user_frac, CTLTYPE_UINT | CTLFLAG_RW, 183 0, sizeof(uint32_t), user_frac_sysctl, "I", 184 "Desired user fraction of cpu time"); 185 186 static uint32_t reg_frac_count = 0; 187 static uint32_t reg_frac = 20 ; 188 static int reg_frac_sysctl(SYSCTL_HANDLER_ARGS) 189 { 190 uint32_t val = reg_frac; 191 int error; 192 193 error = sysctl_handle_int(oidp, &val, 0, req); 194 if (error || !req->newptr ) 195 return (error); 196 if (val < 1 || val > hz) 197 return (EINVAL); 198 199 mtx_lock(&poll_mtx); 200 reg_frac = val; 201 if (reg_frac_count >= reg_frac) 202 reg_frac_count = 0; 203 mtx_unlock(&poll_mtx); 204 205 return (0); 206 } 207 SYSCTL_PROC(_kern_polling, OID_AUTO, reg_frac, CTLTYPE_UINT | CTLFLAG_RW, 208 0, sizeof(uint32_t), reg_frac_sysctl, "I", 209 "Every this many cycles check registers"); 210 211 static uint32_t short_ticks; 212 SYSCTL_UINT(_kern_polling, OID_AUTO, short_ticks, CTLFLAG_RD, 213 &short_ticks, 0, "Hardclock ticks shorter than they should be"); 214 215 static uint32_t lost_polls; 216 SYSCTL_UINT(_kern_polling, OID_AUTO, lost_polls, CTLFLAG_RD, 217 &lost_polls, 0, "How many times we would have lost a poll tick"); 218 219 static uint32_t pending_polls; 220 SYSCTL_UINT(_kern_polling, OID_AUTO, pending_polls, CTLFLAG_RD, 221 &pending_polls, 0, "Do we need to poll again"); 222 223 static int residual_burst = 0; 224 SYSCTL_INT(_kern_polling, OID_AUTO, residual_burst, CTLFLAG_RD, 225 &residual_burst, 0, "# of residual cycles in burst"); 226 227 static uint32_t poll_handlers; /* next free entry in pr[]. */ 228 SYSCTL_UINT(_kern_polling, OID_AUTO, handlers, CTLFLAG_RD, 229 &poll_handlers, 0, "Number of registered poll handlers"); 230 231 static int polling = 0; 232 SYSCTL_PROC(_kern_polling, OID_AUTO, enable, CTLTYPE_UINT | CTLFLAG_RW, 233 0, sizeof(int), poll_switch, "I", "Switch polling for all interfaces"); 234 235 static uint32_t phase; 236 SYSCTL_UINT(_kern_polling, OID_AUTO, phase, CTLFLAG_RD, 237 &phase, 0, "Polling phase"); 238 239 static uint32_t suspect; 240 SYSCTL_UINT(_kern_polling, OID_AUTO, suspect, CTLFLAG_RD, 241 &suspect, 0, "suspect event"); 242 243 static uint32_t stalled; 244 SYSCTL_UINT(_kern_polling, OID_AUTO, stalled, CTLFLAG_RD, 245 &stalled, 0, "potential stalls"); 246 247 static uint32_t idlepoll_sleeping; /* idlepoll is sleeping */ 248 SYSCTL_UINT(_kern_polling, OID_AUTO, idlepoll_sleeping, CTLFLAG_RD, 249 &idlepoll_sleeping, 0, "idlepoll is sleeping"); 250 251 252 #define POLL_LIST_LEN 128 253 struct pollrec { 254 poll_handler_t *handler; 255 struct ifnet *ifp; 256 }; 257 258 static struct pollrec pr[POLL_LIST_LEN]; 259 260 static void 261 init_device_poll(void) 262 { 263 264 mtx_init(&poll_mtx, "polling", NULL, MTX_DEF); 265 netisr_register(NETISR_POLL, (netisr_t *)netisr_poll, NULL, 0); 266 netisr_register(NETISR_POLLMORE, (netisr_t *)netisr_pollmore, NULL, 0); 267 } 268 SYSINIT(device_poll, SI_SUB_CLOCKS, SI_ORDER_MIDDLE, init_device_poll, NULL); 269 270 271 /* 272 * Hook from hardclock. Tries to schedule a netisr, but keeps track 273 * of lost ticks due to the previous handler taking too long. 274 * Normally, this should not happen, because polling handler should 275 * run for a short time. However, in some cases (e.g. when there are 276 * changes in link status etc.) the drivers take a very long time 277 * (even in the order of milliseconds) to reset and reconfigure the 278 * device, causing apparent lost polls. 279 * 280 * The first part of the code is just for debugging purposes, and tries 281 * to count how often hardclock ticks are shorter than they should, 282 * meaning either stray interrupts or delayed events. 283 */ 284 void 285 hardclock_device_poll(void) 286 { 287 static struct timeval prev_t, t; 288 int delta; 289 290 if (poll_handlers == 0) 291 return; 292 293 microuptime(&t); 294 delta = (t.tv_usec - prev_t.tv_usec) + 295 (t.tv_sec - prev_t.tv_sec)*1000000; 296 if (delta * hz < 500000) 297 short_ticks++; 298 else 299 prev_t = t; 300 301 if (pending_polls > 100) { 302 /* 303 * Too much, assume it has stalled (not always true 304 * see comment above). 305 */ 306 stalled++; 307 pending_polls = 0; 308 phase = 0; 309 } 310 311 if (phase <= 2) { 312 if (phase != 0) 313 suspect++; 314 phase = 1; 315 schednetisrbits(1 << NETISR_POLL | 1 << NETISR_POLLMORE); 316 phase = 2; 317 } 318 if (pending_polls++ > 0) 319 lost_polls++; 320 } 321 322 /* 323 * ether_poll is called from the idle loop. 324 */ 325 void 326 ether_poll(int count) 327 { 328 int i; 329 330 mtx_lock(&poll_mtx); 331 332 if (count > poll_each_burst) 333 count = poll_each_burst; 334 335 for (i = 0 ; i < poll_handlers ; i++) 336 pr[i].handler(pr[i].ifp, POLL_ONLY, count); 337 338 mtx_unlock(&poll_mtx); 339 } 340 341 /* 342 * netisr_pollmore is called after other netisr's, possibly scheduling 343 * another NETISR_POLL call, or adapting the burst size for the next cycle. 344 * 345 * It is very bad to fetch large bursts of packets from a single card at once, 346 * because the burst could take a long time to be completely processed, or 347 * could saturate the intermediate queue (ipintrq or similar) leading to 348 * losses or unfairness. To reduce the problem, and also to account better for 349 * time spent in network-related processing, we split the burst in smaller 350 * chunks of fixed size, giving control to the other netisr's between chunks. 351 * This helps in improving the fairness, reducing livelock (because we 352 * emulate more closely the "process to completion" that we have with 353 * fastforwarding) and accounting for the work performed in low level 354 * handling and forwarding. 355 */ 356 357 static struct timeval poll_start_t; 358 359 void 360 netisr_pollmore() 361 { 362 struct timeval t; 363 int kern_load; 364 365 mtx_lock(&poll_mtx); 366 phase = 5; 367 if (residual_burst > 0) { 368 schednetisrbits(1 << NETISR_POLL | 1 << NETISR_POLLMORE); 369 mtx_unlock(&poll_mtx); 370 /* will run immediately on return, followed by netisrs */ 371 return; 372 } 373 /* here we can account time spent in netisr's in this tick */ 374 microuptime(&t); 375 kern_load = (t.tv_usec - poll_start_t.tv_usec) + 376 (t.tv_sec - poll_start_t.tv_sec)*1000000; /* us */ 377 kern_load = (kern_load * hz) / 10000; /* 0..100 */ 378 if (kern_load > (100 - user_frac)) { /* try decrease ticks */ 379 if (poll_burst > 1) 380 poll_burst--; 381 } else { 382 if (poll_burst < poll_burst_max) 383 poll_burst++; 384 } 385 386 pending_polls--; 387 if (pending_polls == 0) /* we are done */ 388 phase = 0; 389 else { 390 /* 391 * Last cycle was long and caused us to miss one or more 392 * hardclock ticks. Restart processing again, but slightly 393 * reduce the burst size to prevent that this happens again. 394 */ 395 poll_burst -= (poll_burst / 8); 396 if (poll_burst < 1) 397 poll_burst = 1; 398 schednetisrbits(1 << NETISR_POLL | 1 << NETISR_POLLMORE); 399 phase = 6; 400 } 401 mtx_unlock(&poll_mtx); 402 } 403 404 /* 405 * netisr_poll is scheduled by schednetisr when appropriate, typically once 406 * per tick. 407 */ 408 static void 409 netisr_poll(void) 410 { 411 int i, cycles; 412 enum poll_cmd arg = POLL_ONLY; 413 414 mtx_lock(&poll_mtx); 415 phase = 3; 416 if (residual_burst == 0) { /* first call in this tick */ 417 microuptime(&poll_start_t); 418 if (++reg_frac_count == reg_frac) { 419 arg = POLL_AND_CHECK_STATUS; 420 reg_frac_count = 0; 421 } 422 423 residual_burst = poll_burst; 424 } 425 cycles = (residual_burst < poll_each_burst) ? 426 residual_burst : poll_each_burst; 427 residual_burst -= cycles; 428 429 for (i = 0 ; i < poll_handlers ; i++) 430 pr[i].handler(pr[i].ifp, arg, cycles); 431 432 phase = 4; 433 mtx_unlock(&poll_mtx); 434 } 435 436 /* 437 * Try to register routine for polling. Returns 0 if successful 438 * (and polling should be enabled), error code otherwise. 439 * A device is not supposed to register itself multiple times. 440 * 441 * This is called from within the *_ioctl() functions. 442 */ 443 int 444 ether_poll_register(poll_handler_t *h, struct ifnet *ifp) 445 { 446 int i; 447 448 KASSERT(h != NULL, ("%s: handler is NULL", __func__)); 449 KASSERT(ifp != NULL, ("%s: ifp is NULL", __func__)); 450 451 mtx_lock(&poll_mtx); 452 if (poll_handlers >= POLL_LIST_LEN) { 453 /* 454 * List full, cannot register more entries. 455 * This should never happen; if it does, it is probably a 456 * broken driver trying to register multiple times. Checking 457 * this at runtime is expensive, and won't solve the problem 458 * anyways, so just report a few times and then give up. 459 */ 460 static int verbose = 10 ; 461 if (verbose >0) { 462 log(LOG_ERR, "poll handlers list full, " 463 "maybe a broken driver ?\n"); 464 verbose--; 465 } 466 mtx_unlock(&poll_mtx); 467 return (ENOMEM); /* no polling for you */ 468 } 469 470 for (i = 0 ; i < poll_handlers ; i++) 471 if (pr[i].ifp == ifp && pr[i].handler != NULL) { 472 mtx_unlock(&poll_mtx); 473 log(LOG_DEBUG, "ether_poll_register: %s: handler" 474 " already registered\n", ifp->if_xname); 475 return (EEXIST); 476 } 477 478 pr[poll_handlers].handler = h; 479 pr[poll_handlers].ifp = ifp; 480 poll_handlers++; 481 mtx_unlock(&poll_mtx); 482 if (idlepoll_sleeping) 483 wakeup(&idlepoll_sleeping); 484 return (0); 485 } 486 487 /* 488 * Remove interface from the polling list. Called from *_ioctl(), too. 489 */ 490 int 491 ether_poll_deregister(struct ifnet *ifp) 492 { 493 int i; 494 495 KASSERT(ifp != NULL, ("%s: ifp is NULL", __func__)); 496 497 mtx_lock(&poll_mtx); 498 499 for (i = 0 ; i < poll_handlers ; i++) 500 if (pr[i].ifp == ifp) /* found it */ 501 break; 502 if (i == poll_handlers) { 503 log(LOG_DEBUG, "ether_poll_deregister: %s: not found!\n", 504 ifp->if_xname); 505 mtx_unlock(&poll_mtx); 506 return (ENOENT); 507 } 508 poll_handlers--; 509 if (i < poll_handlers) { /* Last entry replaces this one. */ 510 pr[i].handler = pr[poll_handlers].handler; 511 pr[i].ifp = pr[poll_handlers].ifp; 512 } 513 mtx_unlock(&poll_mtx); 514 return (0); 515 } 516 517 /* 518 * Legacy interface for turning polling on all interfaces at one time. 519 */ 520 static int 521 poll_switch(SYSCTL_HANDLER_ARGS) 522 { 523 struct ifnet *ifp; 524 int error; 525 int val = polling; 526 527 error = sysctl_handle_int(oidp, &val, 0, req); 528 if (error || !req->newptr ) 529 return (error); 530 531 if (val == polling) 532 return (0); 533 534 if (val < 0 || val > 1) 535 return (EINVAL); 536 537 polling = val; 538 539 IFNET_RLOCK(); 540 TAILQ_FOREACH(ifp, &ifnet, if_link) { 541 if (ifp->if_capabilities & IFCAP_POLLING) { 542 struct ifreq ifr; 543 544 if (val == 1) 545 ifr.ifr_reqcap = 546 ifp->if_capenable | IFCAP_POLLING; 547 else 548 ifr.ifr_reqcap = 549 ifp->if_capenable & ~IFCAP_POLLING; 550 IFF_LOCKGIANT(ifp); /* LOR here */ 551 (void) (*ifp->if_ioctl)(ifp, SIOCSIFCAP, (caddr_t)&ifr); 552 IFF_UNLOCKGIANT(ifp); 553 } 554 } 555 IFNET_RUNLOCK(); 556 557 log(LOG_ERR, "kern.polling.enable is deprecated. Use ifconfig(8)"); 558 559 return (0); 560 } 561 562 static void 563 poll_idle(void) 564 { 565 struct thread *td = curthread; 566 struct rtprio rtp; 567 568 rtp.prio = RTP_PRIO_MAX; /* lowest priority */ 569 rtp.type = RTP_PRIO_IDLE; 570 PROC_SLOCK(td->td_proc); 571 rtp_to_pri(&rtp, td); 572 PROC_SUNLOCK(td->td_proc); 573 574 for (;;) { 575 if (poll_in_idle_loop && poll_handlers > 0) { 576 idlepoll_sleeping = 0; 577 ether_poll(poll_each_burst); 578 thread_lock(td); 579 mi_switch(SW_VOL, NULL); 580 thread_unlock(td); 581 } else { 582 idlepoll_sleeping = 1; 583 tsleep(&idlepoll_sleeping, 0, "pollid", hz * 3); 584 } 585 } 586 } 587 588 static struct proc *idlepoll; 589 static struct kproc_desc idlepoll_kp = { 590 "idlepoll", 591 poll_idle, 592 &idlepoll 593 }; 594 SYSINIT(idlepoll, SI_SUB_KTHREAD_VM, SI_ORDER_ANY, kproc_start, 595 &idlepoll_kp); 596