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Comparing libev/ev_linuxaio.c (file contents):
Revision 1.12 by root, Sun Jun 23 23:02:09 2019 UTC vs.
Revision 1.20 by root, Mon Jun 24 20:33:24 2019 UTC

… …
53 * therefore the calculation below will use "exactly" 4kB for the ring buffer 53 * therefore the calculation below will use "exactly" 4kB for the ring buffer
54 */ 54 */
55#define EV_LINUXAIO_DEPTH (128 / 2 - 2 - 1) /* max. number of io events per batch */ 55#define EV_LINUXAIO_DEPTH (128 / 2 - 2 - 1) /* max. number of io events per batch */
56 56
57/*****************************************************************************/ 57/*****************************************************************************/
58/* syscall wrapdadoop */ 58/* syscall wrapdadoop - this section has the raw syscall definitions */
59 59
60#include <sys/syscall.h> /* no glibc wrappers */ 60#include <sys/syscall.h> /* no glibc wrappers */
61 61
62/* aio_abi.h is not versioned in any way, so we cannot test for its existance */ 62/* aio_abi.h is not versioned in any way, so we cannot test for its existance */
63#define IOCB_CMD_POLL 5 63#define IOCB_CMD_POLL 5
… …
80 struct io_event io_events[0]; 80 struct io_event io_events[0];
81}; 81};
82 82
83inline_size 83inline_size
84int 84int
85ev_io_setup (unsigned nr_events, aio_context_t *ctx_idp) 85evsys_io_setup (unsigned nr_events, aio_context_t *ctx_idp)
86{ 86{
87 return syscall (SYS_io_setup, nr_events, ctx_idp); 87 return syscall (SYS_io_setup, nr_events, ctx_idp);
88} 88}
89 89
90inline_size 90inline_size
91int 91int
92ev_io_destroy (aio_context_t ctx_id) 92evsys_io_destroy (aio_context_t ctx_id)
93{ 93{
94 return syscall (SYS_io_destroy, ctx_id); 94 return syscall (SYS_io_destroy, ctx_id);
95} 95}
96 96
97inline_size 97inline_size
98int 98int
99ev_io_submit (aio_context_t ctx_id, long nr, struct iocb *cbp[]) 99evsys_io_submit (aio_context_t ctx_id, long nr, struct iocb *cbp[])
100{ 100{
101 return syscall (SYS_io_submit, ctx_id, nr, cbp); 101 return syscall (SYS_io_submit, ctx_id, nr, cbp);
102} 102}
103 103
104inline_size 104inline_size
105int 105int
106ev_io_cancel (aio_context_t ctx_id, struct iocb *cbp, struct io_event *result) 106evsys_io_cancel (aio_context_t ctx_id, struct iocb *cbp, struct io_event *result)
107{ 107{
108 return syscall (SYS_io_cancel, ctx_id, cbp, result); 108 return syscall (SYS_io_cancel, ctx_id, cbp, result);
109} 109}
110 110
111inline_size 111inline_size
112int 112int
113ev_io_getevents (aio_context_t ctx_id, long min_nr, long nr, struct io_event *events, struct timespec *timeout) 113evsys_io_getevents (aio_context_t ctx_id, long min_nr, long nr, struct io_event *events, struct timespec *timeout)
114{ 114{
115 return syscall (SYS_io_getevents, ctx_id, min_nr, nr, events, timeout); 115 return syscall (SYS_io_getevents, ctx_id, min_nr, nr, events, timeout);
116} 116}
117 117
118/*****************************************************************************/ 118/*****************************************************************************/
… …
164 iocb->io.aio_reqprio = 0; 164 iocb->io.aio_reqprio = 0;
165 } 165 }
166#endif 166#endif
167 167
168 if (iocb->io.aio_buf) 168 if (iocb->io.aio_buf)
169 ev_io_cancel (linuxaio_ctx, &iocb->io, (struct io_event *)0); /* always returns an error relevant kernels */ 169 evsys_io_cancel (linuxaio_ctx, &iocb->io, (struct io_event *)0); /* always returns an error relevant kernels */
170 170
171 if (nev) 171 if (nev)
172 { 172 {
173 iocb->io.aio_data = fd; 173 iocb->io.aio_data = fd;
174 iocb->io.aio_fildes = fd; 174 iocb->io.aio_fildes = fd;
… …
182 array_needsize (struct iocb *, linuxaio_submits, linuxaio_submitmax, linuxaio_submitcnt, array_needsize_noinit); 182 array_needsize (struct iocb *, linuxaio_submits, linuxaio_submitmax, linuxaio_submitcnt, array_needsize_noinit);
183 linuxaio_submits [linuxaio_submitcnt - 1] = &iocb->io; 183 linuxaio_submits [linuxaio_submitcnt - 1] = &iocb->io;
184 } 184 }
185} 185}
186 186
187#if EPOLL_FALLBACK
188
189static void
190linuxaio_rearm_epoll (EV_P_ struct iocb *iocb, int op)
191{
192 struct epoll_event eev;
193
194 eev.events = EPOLLONESHOT;
195 if (iocb->aio_buf & POLLIN ) eev.events |= EPOLLIN ;
196 if (iocb->aio_buf & POLLOUT) eev.events |= EPOLLOUT;
197 eev.data.fd = iocb->aio_fildes;
198
199 if (epoll_ctl (backend_fd, op, iocb->aio_fildes, &eev) < 0)
200 ev_syserr ("(libeio) linuxaio epoll_ctl");
201}
202
203static void
204linuxaio_epoll_cb (EV_P_ struct ev_io *w, int revents)
205{
206 struct epoll_event events[16];
207
208 for (;;)
209 {
210 int idx;
211 int res = epoll_wait (backend_fd, events, sizeof (events) / sizeof (events [0]), 0);
212
213 if (expect_false (res < 0))
214 ev_syserr ("(libev) linuxaio epoll_wait");
215 else if (!res)
216 break;
217
218 for (idx = res; idx--; )
219 {
220 int fd = events [idx].data.fd;
221 uint32_t ev = events [idx].events;
222
223 assert (("libev: iocb fd must be in-bounds", fd >= 0 && fd < anfdmax));
224
225 linuxaio_rearm_epoll (EV_A_ &linuxaio_iocbps [fd]->io, EPOLL_CTL_MOD);
226
227 fd_event (EV_A_ fd,
228 (ev & (EPOLLOUT | EPOLLERR | EPOLLHUP) ? EV_WRITE : 0)
229 | (ev & (EPOLLIN | EPOLLERR | EPOLLHUP) ? EV_READ : 0));
230 }
231
232 if (res < sizeof (events) / sizeof (events [0]))
233 break;
234 }
235}
236
237#endif
238
187static void 239static void
188linuxaio_parse_events (EV_P_ struct io_event *ev, int nr) 240linuxaio_parse_events (EV_P_ struct io_event *ev, int nr)
189{ 241{
190 while (nr) 242 while (nr)
191 { 243 {
192 int fd = ev->data; 244 int fd = ev->data;
193 int res = ev->res; 245 int res = ev->res;
194 246
195 assert (("libev: iocb fd must be in-bounds", fd >= 0 && fd < anfdmax)); 247 assert (("libev: iocb fd must be in-bounds", fd >= 0 && fd < anfdmax));
196 248
197 /* linux aio is oneshot: rearm fd */ 249 /* linux aio is oneshot: rearm fd. TODO: this does more work than needed */
198 linuxaio_iocbps [fd]->io.aio_buf = 0; 250 linuxaio_iocbps [fd]->io.aio_buf = 0;
199 anfds [fd].events = 0; 251 anfds [fd].events = 0;
200 fd_change (EV_A_ fd, 0); 252 fd_change (EV_A_ fd, 0);
201 253
202 /* feed events, we do not expect or handle POLLNVAL */ 254 /* feed events, we do not expect or handle POLLNVAL */
203 if (ecb_expect_false (res & POLLNVAL)) 255 if (expect_false (res & POLLNVAL))
204 fd_kill (EV_A_ fd); 256 fd_kill (EV_A_ fd);
205 else 257 else
206 fd_event ( 258 fd_event (
207 EV_A_ 259 EV_A_
208 fd, 260 fd,
… …
219static int 271static int
220linuxaio_get_events_from_ring (EV_P) 272linuxaio_get_events_from_ring (EV_P)
221{ 273{
222 struct aio_ring *ring = (struct aio_ring *)linuxaio_ctx; 274 struct aio_ring *ring = (struct aio_ring *)linuxaio_ctx;
223 275
224 unsigned head = ring->head; 276 /* the kernel reads and writes both of these variables, */
277 /* as a C extension, we assume that volatile use here */
278 /* both makes reads atomic and once-only */
279 unsigned head = *(volatile unsigned *)&ring->head;
225 unsigned tail = *(volatile unsigned *)&ring->tail; 280 unsigned tail = *(volatile unsigned *)&ring->tail;
226 281
227 if (head == tail) 282 if (head == tail)
228 return 0; 283 return 0;
229 284
230 /* bail out if the ring buffer doesn't match the expected layout */ 285 /* bail out if the ring buffer doesn't match the expected layout */
231 if (ecb_expect_false (ring->magic != AIO_RING_MAGIC) 286 if (expect_false (ring->magic != AIO_RING_MAGIC)
232 || ring->incompat_features != AIO_RING_INCOMPAT_FEATURES 287 || ring->incompat_features != AIO_RING_INCOMPAT_FEATURES
233 || ring->header_length != sizeof (struct aio_ring)) /* TODO: or use it to find io_event[0]? */ 288 || ring->header_length != sizeof (struct aio_ring)) /* TODO: or use it to find io_event[0]? */
234 return 0; 289 return 0;
235 290
236 /* make sure the events up to tail are visible */ 291 /* make sure the events up to tail are visible */
237 ECB_MEMORY_FENCE_ACQUIRE; 292 ECB_MEMORY_FENCE_ACQUIRE;
238 293
… …
243 { 298 {
244 linuxaio_parse_events (EV_A_ ring->io_events + head, ring->nr - head); 299 linuxaio_parse_events (EV_A_ ring->io_events + head, ring->nr - head);
245 linuxaio_parse_events (EV_A_ ring->io_events, tail); 300 linuxaio_parse_events (EV_A_ ring->io_events, tail);
246 } 301 }
247 302
303 /* TODO: we only need a compiler barrier here, not a read fence */
304 ECB_MEMORY_FENCE_RELEASE;
305 /* as an extension to C, we hope that the volatile will make this atomic and once-only */
248 *(volatile unsigned *)&ring->head = tail; 306 *(volatile unsigned *)&ring->head = tail;
249 /* make sure kernel can see our new head value - probably not required */ 307 /* make sure kernel can see our new head value - probably not required */
250 ECB_MEMORY_FENCE_RELEASE; 308 ECB_MEMORY_FENCE_RELEASE;
251 309
252 return 1; 310 return 1;
… …
256inline_size 314inline_size
257void 315void
258linuxaio_get_events (EV_P_ ev_tstamp timeout) 316linuxaio_get_events (EV_P_ ev_tstamp timeout)
259{ 317{
260 struct timespec ts; 318 struct timespec ts;
261 struct io_event ioev; 319 struct io_event ioev[1];
262 int res; 320 int res;
263 321
264 if (linuxaio_get_events_from_ring (EV_A)) 322 if (linuxaio_get_events_from_ring (EV_A))
265 return; 323 return;
266 324
267 /* no events, so wait for at least one, then poll ring buffer again */ 325 /* no events, so wait for at least one, then poll ring buffer again */
268 /* this degrades to one event per loop iteration */ 326 /* this degrades to one event per loop iteration */
269 /* if the ring buffer changes layout, but so be it */ 327 /* if the ring buffer changes layout, but so be it */
270 328
329 EV_RELEASE_CB;
330
271 ts.tv_sec = (long)timeout; 331 ts.tv_sec = (long)timeout;
272 ts.tv_nsec = (long)((timeout - ts.tv_sec) * 1e9); 332 ts.tv_nsec = (long)((timeout - ts.tv_sec) * 1e9);
273 333
274 res = ev_io_getevents (linuxaio_ctx, 1, 1, &ioev, &ts); 334 res = evsys_io_getevents (linuxaio_ctx, 1, sizeof (ioev) / sizeof (ioev [0]), ioev, &ts);
335
336 EV_ACQUIRE_CB;
275 337
276 if (res < 0) 338 if (res < 0)
277 if (errno == EINTR) 339 if (errno == EINTR)
278 /* ignored */; 340 /* ignored */;
279 else 341 else
280 ev_syserr ("(libev) linuxaio io_getevents"); 342 ev_syserr ("(libev) linuxaio io_getevents");
281 else if (res) 343 else if (res)
282 { 344 {
283 /* at least one event received, handle it and any remaining ones in the ring buffer */ 345 /* at least one event received, handle it and any remaining ones in the ring buffer */
284 linuxaio_parse_events (EV_A_ &ioev, 1); 346 linuxaio_parse_events (EV_A_ ioev, res);
285 linuxaio_get_events_from_ring (EV_A); 347 linuxaio_get_events_from_ring (EV_A);
286 } 348 }
287} 349}
288
289#if EPOLL_FALLBACK
290static void
291linuxaio_rearm_epoll (EV_P_ struct iocb *iocb, int op)
292{
293 struct epoll_event eev;
294
295 eev.events = EPOLLONESHOT;
296 if (iocb->aio_buf & POLLIN ) eev.events |= EPOLLIN ;
297 if (iocb->aio_buf & POLLOUT) eev.events |= EPOLLOUT;
298 eev.data.fd = iocb->aio_fildes;
299
300 if (epoll_ctl (backend_fd, op, iocb->aio_fildes, &eev) < 0)
301 ev_syserr ("(libeio) linuxaio epoll_ctl");
302}
303#endif
304 350
305static void 351static void
306linuxaio_poll (EV_P_ ev_tstamp timeout) 352linuxaio_poll (EV_P_ ev_tstamp timeout)
307{ 353{
308 int submitted; 354 int submitted;
… …
312 /* io_submit might return less than the requested number of iocbs */ 358 /* io_submit might return less than the requested number of iocbs */
313 /* this is, afaics, only because of errors, but we go by the book and use a loop, */ 359 /* this is, afaics, only because of errors, but we go by the book and use a loop, */
314 /* which allows us to pinpoint the errornous iocb */ 360 /* which allows us to pinpoint the errornous iocb */
315 for (submitted = 0; submitted < linuxaio_submitcnt; ) 361 for (submitted = 0; submitted < linuxaio_submitcnt; )
316 { 362 {
363#if 0
364 int res;
365 if (linuxaio_submits[submitted]->aio_fildes == backend_fd)
366 res = evsys_io_submit (linuxaio_ctx, 1, linuxaio_submits + submitted);
367 else
368 { res = -1; errno = EINVAL; };
369#else
317 int res = ev_io_submit (linuxaio_ctx, linuxaio_submitcnt - submitted, linuxaio_submits + submitted); 370 int res = evsys_io_submit (linuxaio_ctx, linuxaio_submitcnt - submitted, linuxaio_submits + submitted);
371#endif
318 372
319 if (ecb_expect_false (res < 0)) 373 if (expect_false (res < 0))
320 if (errno == EAGAIN) 374 if (errno == EAGAIN)
321 { 375 {
322 /* This happens when the ring buffer is full, at least. I assume this means 376 /* This happens when the ring buffer is full, at least. I assume this means
323 * that the event was queued synchronously during io_submit, and thus 377 * that the event was queued synchronously during io_submit, and thus
324 * the buffer overflowed. 378 * the buffer overflowed.
325 * In this case, we just try in next loop iteration. 379 * In this case, we just try in next loop iteration.
326 * This should not result in a few fds taking priority, as the interface 380 * This should not result in a few fds taking priority, as the interface
327 * is one-shot, and we submit iocb's in a round-robin fashion. 381 * is one-shot, and we submit iocb's in a round-robin fashion.
382 * TODO: maybe make "submitted" persistent, so we don't have to memmove?
328 */ 383 */
384 if (ecb_expect_false (submitted))
385 {
329 memmove (linuxaio_submits, linuxaio_submits + submitted, (linuxaio_submitcnt - submitted) * sizeof (*linuxaio_submits)); 386 memmove (linuxaio_submits, linuxaio_submits + submitted, (linuxaio_submitcnt - submitted) * sizeof (*linuxaio_submits));
330 linuxaio_submitcnt -= submitted; 387 linuxaio_submitcnt -= submitted;
388 }
389
331 timeout = 0; 390 timeout = 0;
332 break; 391 break;
333 } 392 }
334#if EPOLL_FALLBACK 393#if EPOLL_FALLBACK
335 else if (errno == EINVAL) 394 else if (errno == EINVAL)
336 { 395 {
337 /* This hapΓΌpens for unsupported fds, officially, but in my testing, 396 /* This happens for unsupported fds, officially, but in my testing,
338 * also randomly happens for supported fds. We fall back to good old 397 * also randomly happens for supported fds. We fall back to good old
339 * poll() here, under the assumption that this is a very rare case. 398 * poll() here, under the assumption that this is a very rare case.
399 * See https://lore.kernel.org/patchwork/patch/1047453/ to see
400 * discussion about such a case (ttys) where polling for POLLIN
401 * fails but POLLIN|POLLOUT works.
340 */ 402 */
341 struct iocb *iocb = linuxaio_submits [submitted]; 403 struct iocb *iocb = linuxaio_submits [submitted];
342 res = 1; /* skip this iocb */ 404 res = 1; /* skip this iocb */
343 405
344 linuxaio_rearm_epoll (EV_A_ iocb, EPOLL_CTL_ADD); 406 linuxaio_rearm_epoll (EV_A_ iocb, EPOLL_CTL_ADD);
… …
356 /* second phase: fetch and parse events */ 418 /* second phase: fetch and parse events */
357 419
358 linuxaio_get_events (EV_A_ timeout); 420 linuxaio_get_events (EV_A_ timeout);
359} 421}
360 422
361#if EPOLL_FALLBACK
362
363static void
364linuxaio_epoll_cb (EV_P_ struct ev_io *w, int revents)
365{
366 struct epoll_event events[16];
367
368 for (;;)
369 {
370 int idx;
371 int res = epoll_wait (backend_fd, events, sizeof (events) / sizeof (events [0]), 0);
372
373 if (ecb_expect_false (res < 0))
374 ev_syserr ("(libev) linuxaio epoll_wait");
375 else if (!res)
376 break;
377
378 for (idx = res; idx--; )
379 {
380 int fd = events [idx].data.fd;
381 uint32_t ev = events [idx].events;
382
383 assert (("libev: iocb fd must be in-bounds", fd >= 0 && fd < anfdmax));
384
385 linuxaio_rearm_epoll (EV_A_ &linuxaio_iocbps [fd]->io, EPOLL_CTL_MOD);
386
387 fd_event (EV_A_ fd,
388 (ev & (EPOLLOUT | EPOLLERR | EPOLLHUP) ? EV_WRITE : 0)
389 | (ev & (EPOLLIN | EPOLLERR | EPOLLHUP) ? EV_READ : 0));
390 }
391
392 if (res < sizeof (events) / sizeof (events [0]))
393 break;
394 }
395}
396
397#endif
398
399inline_size 423inline_size
400int 424int
401linuxaio_init (EV_P_ int flags) 425linuxaio_init (EV_P_ int flags)
402{ 426{
403 /* would be great to have a nice test for IOCB_CMD_POLL instead */ 427 /* would be great to have a nice test for IOCB_CMD_POLL instead */
404 /* also: test some semi-common fd types, such as files and ttys in recommended_backends */ 428 /* also: test some semi-common fd types, such as files and ttys in recommended_backends */
405 if (ev_linux_version () < 0x041200) /* 4.18 introduced IOCB_CMD_POLL */ 429#if EPOLL_FALLBACK
430 /* 4.19 made epoll work */
431 if (ev_linux_version () < 0x041300)
406 return 0; 432 return 0;
433#else
434 /* 4.18 introduced IOCB_CMD_POLL */
435 if (ev_linux_version () < 0x041200)
436 return 0;
437#endif
407 438
408 linuxaio_ctx = 0; 439 linuxaio_ctx = 0;
409 if (ev_io_setup (EV_LINUXAIO_DEPTH, &linuxaio_ctx) < 0) 440 if (evsys_io_setup (EV_LINUXAIO_DEPTH, &linuxaio_ctx) < 0)
410 return 0; 441 return 0;
411 442
412#if EPOLL_FALLBACK 443#if EPOLL_FALLBACK
413 backend_fd = ev_epoll_create (); 444 backend_fd = ev_epoll_create ();
414 if (backend_fd < 0) 445 if (backend_fd < 0)
415 { 446 {
416 ev_io_destroy (linuxaio_ctx); 447 evsys_io_destroy (linuxaio_ctx);
417 return 0; 448 return 0;
418 } 449 }
419 450
420 ev_io_init (EV_A_ &linuxaio_epoll_w, linuxaio_epoll_cb, backend_fd, EV_READ); 451 ev_io_init (EV_A_ &linuxaio_epoll_w, linuxaio_epoll_cb, backend_fd, EV_READ);
452 ev_set_priority (&linuxaio_epoll_w, EV_MAXPRI);
421 ev_io_start (EV_A_ &linuxaio_epoll_w); 453 ev_io_start (EV_A_ &linuxaio_epoll_w);
454 ev_unref (EV_A); /* watcher should not keep loop alive */
422#endif 455#endif
423 456
424 backend_modify = linuxaio_modify; 457 backend_modify = linuxaio_modify;
425 backend_poll = linuxaio_poll; 458 backend_poll = linuxaio_poll;
426 459
… …
452 /* this frees all iocbs, which is very heavy-handed */ 485 /* this frees all iocbs, which is very heavy-handed */
453 linuxaio_destroy (EV_A); 486 linuxaio_destroy (EV_A);
454 linuxaio_submitcnt = 0; /* all pointers were invalidated */ 487 linuxaio_submitcnt = 0; /* all pointers were invalidated */
455 488
456 linuxaio_ctx = 0; 489 linuxaio_ctx = 0;
457 while (ev_io_setup (EV_LINUXAIO_DEPTH, &linuxaio_ctx) < 0) 490 while (evsys_io_setup (EV_LINUXAIO_DEPTH, &linuxaio_ctx) < 0)
458 ev_syserr ("(libev) linuxaio io_setup"); 491 ev_syserr ("(libev) linuxaio io_setup");
459 492
460#if EPOLL_FALLBACK 493#if EPOLL_FALLBACK
461 while ((backend_fd = ev_epoll_create ()) < 0) 494 while ((backend_fd = ev_epoll_create ()) < 0)
462 ev_syserr ("(libev) linuxaio epoll_create"); 495 ev_syserr ("(libev) linuxaio epoll_create");
463 496
464 ev_io_stop (EV_A_ &linuxaio_epoll_w); 497 ev_io_stop (EV_A_ &linuxaio_epoll_w);
465 ev_io_init (EV_A_ &linuxaio_epoll_w, linuxaio_epoll_cb, backend_fd, EV_READ); 498 ev_io_init (EV_A_ &linuxaio_epoll_w, linuxaio_epoll_cb, backend_fd, EV_READ);
466 ev_io_start (EV_A_ &linuxaio_epoll_w); 499 ev_io_start (EV_A_ &linuxaio_epoll_w);
467 ev_unref (EV_A); /* watcher should not keep loop alive */
468#endif 500#endif
469 501
470 fd_rearm_all (EV_A); 502 fd_rearm_all (EV_A);
471} 503}
472 504

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