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Comparing libev/ev_linuxaio.c (file contents):
Revision 1.32 by root, Tue Jun 25 18:07:44 2019 UTC vs.
Revision 1.43 by root, Mon Jul 1 21:47:42 2019 UTC

… …
100 * not only is this totally undocumented, not even the source code 100 * not only is this totally undocumented, not even the source code
101 * can tell you what the future semantics of compat_features and 101 * can tell you what the future semantics of compat_features and
102 * incompat_features are, or what header_length actually is for. 102 * incompat_features are, or what header_length actually is for.
103 */ 103 */
104#define AIO_RING_MAGIC 0xa10a10a1 104#define AIO_RING_MAGIC 0xa10a10a1
105#define AIO_RING_INCOMPAT_FEATURES 0 105#define EV_AIO_RING_INCOMPAT_FEATURES 0
106struct aio_ring 106struct aio_ring
107{ 107{
108 unsigned id; /* kernel internal index number */ 108 unsigned id; /* kernel internal index number */
109 unsigned nr; /* number of io_events */ 109 unsigned nr; /* number of io_events */
110 unsigned head; /* Written to by userland or by kernel. */ 110 unsigned head; /* Written to by userland or by kernel. */
… …
115 unsigned incompat_features; 115 unsigned incompat_features;
116 unsigned header_length; /* size of aio_ring */ 116 unsigned header_length; /* size of aio_ring */
117 117
118 struct io_event io_events[0]; 118 struct io_event io_events[0];
119}; 119};
120
121/*
122 * define some syscall wrappers for common architectures
123 * this is mostly for nice looks during debugging, not performance.
124 * our syscalls return < 0, not == -1, on error. which is good
125 * enough for linux aio.
126 * TODO: arm is also common nowadays, maybe even mips and x86
127 * TODO: after implementing this, it suddenly looks like overkill, but its hard to remove...
128 */
129#if __GNUC__ && __linux && ECB_AMD64 && !defined __OPTIMIZE_SIZE__
130 /* the costly errno access probably kills this for size optimisation */
131
132 #define ev_syscall(nr,narg,arg1,arg2,arg3,arg4,arg5) \
133 ({ \
134 long res; \
135 register unsigned long r5 __asm__ ("r8" ); \
136 register unsigned long r4 __asm__ ("r10"); \
137 register unsigned long r3 __asm__ ("rdx"); \
138 register unsigned long r2 __asm__ ("rsi"); \
139 register unsigned long r1 __asm__ ("rdi"); \
140 if (narg >= 5) r5 = (unsigned long)(arg5); \
141 if (narg >= 4) r4 = (unsigned long)(arg4); \
142 if (narg >= 3) r3 = (unsigned long)(arg3); \
143 if (narg >= 2) r2 = (unsigned long)(arg2); \
144 if (narg >= 1) r1 = (unsigned long)(arg1); \
145 __asm__ __volatile__ ( \
146 "syscall\n\t" \
147 : "=a" (res) \
148 : "0" (nr), "r" (r1), "r" (r2), "r" (r3), "r" (r4), "r" (r5) \
149 : "cc", "r11", "cx", "memory"); \
150 errno = -res; \
151 res; \
152 })
153
154#endif
155
156#ifdef ev_syscall
157 #define ev_syscall0(nr) ev_syscall (nr, 0, 0, 0, 0, 0, 0
158 #define ev_syscall1(nr,arg1) ev_syscall (nr, 1, arg1, 0, 0, 0, 0)
159 #define ev_syscall2(nr,arg1,arg2) ev_syscall (nr, 2, arg1, arg2, 0, 0, 0)
160 #define ev_syscall3(nr,arg1,arg2,arg3) ev_syscall (nr, 3, arg1, arg2, arg3, 0, 0)
161 #define ev_syscall4(nr,arg1,arg2,arg3,arg4) ev_syscall (nr, 3, arg1, arg2, arg3, arg4, 0)
162 #define ev_syscall5(nr,arg1,arg2,arg3,arg4,arg5) ev_syscall (nr, 5, arg1, arg2, arg3, arg4, arg5)
163#else
164 #define ev_syscall0(nr) syscall (nr)
165 #define ev_syscall1(nr,arg1) syscall (nr, arg1)
166 #define ev_syscall2(nr,arg1,arg2) syscall (nr, arg1, arg2)
167 #define ev_syscall3(nr,arg1,arg2,arg3) syscall (nr, arg1, arg2, arg3)
168 #define ev_syscall4(nr,arg1,arg2,arg3,arg4) syscall (nr, arg1, arg2, arg3, arg4)
169 #define ev_syscall5(nr,arg1,arg2,arg3,arg4,arg5) syscall (nr, arg1, arg2, arg3, arg4, arg5)
170#endif
171 120
172inline_size 121inline_size
173int 122int
174evsys_io_setup (unsigned nr_events, aio_context_t *ctx_idp) 123evsys_io_setup (unsigned nr_events, aio_context_t *ctx_idp)
175{ 124{
… …
286linuxaio_modify (EV_P_ int fd, int oev, int nev) 235linuxaio_modify (EV_P_ int fd, int oev, int nev)
287{ 236{
288 array_needsize (ANIOCBP, linuxaio_iocbps, linuxaio_iocbpmax, fd + 1, linuxaio_array_needsize_iocbp); 237 array_needsize (ANIOCBP, linuxaio_iocbps, linuxaio_iocbpmax, fd + 1, linuxaio_array_needsize_iocbp);
289 ANIOCBP iocb = linuxaio_iocbps [fd]; 238 ANIOCBP iocb = linuxaio_iocbps [fd];
290 239
291 if (iocb->io.aio_reqprio < 0) 240 if (ecb_expect_false (iocb->io.aio_reqprio < 0))
292 { 241 {
293 /* we handed this fd over to epoll, so undo this first */ 242 /* we handed this fd over to epoll, so undo this first */
294 /* we do it manually because the optimisations on epoll_modfy won't do us any good */ 243 /* we do it manually because the optimisations on epoll_modify won't do us any good */
295 epoll_ctl (backend_fd, EPOLL_CTL_DEL, fd, 0); 244 epoll_ctl (backend_fd, EPOLL_CTL_DEL, fd, 0);
296 anfds [fd].emask = 0; 245 anfds [fd].emask = 0;
297 iocb->io.aio_reqprio = 0; 246 iocb->io.aio_reqprio = 0;
298 } 247 }
299 248
249 if (ecb_expect_false (iocb->io.aio_buf))
250 {
251 /* iocb active, so cancel it first before resubmit */
252 for (;;)
253 {
254 /* on all relevant kernels, io_cancel fails with EINPROGRESS on "success" */
255 if (ecb_expect_false (evsys_io_cancel (linuxaio_ctx, &iocb->io, (struct io_event *)0) == 0))
256 break;
257
258 if (ecb_expect_true (errno == EINPROGRESS))
259 break;
260
261 /* the EINPROGRESS test is for nicer error message. clumsy. */
262 assert (("libev: linuxaio unexpected io_cancel failed", errno != EINPROGRESS && errno != EINTR));
263 }
264 }
265
300 if (iocb->io.aio_buf) 266 iocb->io.aio_buf =
301 /* io_cancel always returns some error on relevant kernels, but works */ 267 (nev & EV_READ ? POLLIN : 0)
302 evsys_io_cancel (linuxaio_ctx, &iocb->io, (struct io_event *)0); 268 | (nev & EV_WRITE ? POLLOUT : 0);
303 269
304 if (nev) 270 if (nev)
305 { 271 {
306 iocb->io.aio_buf =
307 (nev & EV_READ ? POLLIN : 0)
308 | (nev & EV_WRITE ? POLLOUT : 0);
309
310 /* queue iocb up for io_submit */ 272 /* queue iocb up for io_submit */
311 /* this assumes we only ever get one call per fd per loop iteration */ 273 /* this assumes we only ever get one call per fd per loop iteration */
312 ++linuxaio_submitcnt; 274 ++linuxaio_submitcnt;
313 array_needsize (struct iocb *, linuxaio_submits, linuxaio_submitmax, linuxaio_submitcnt, array_needsize_noinit); 275 array_needsize (struct iocb *, linuxaio_submits, linuxaio_submitmax, linuxaio_submitcnt, array_needsize_noinit);
314 linuxaio_submits [linuxaio_submitcnt - 1] = &iocb->io; 276 linuxaio_submits [linuxaio_submitcnt - 1] = &iocb->io;
… …
319linuxaio_epoll_cb (EV_P_ struct ev_io *w, int revents) 281linuxaio_epoll_cb (EV_P_ struct ev_io *w, int revents)
320{ 282{
321 epoll_poll (EV_A_ 0); 283 epoll_poll (EV_A_ 0);
322} 284}
323 285
324static void 286inline_speed
287void
325linuxaio_fd_rearm (EV_P_ int fd) 288linuxaio_fd_rearm (EV_P_ int fd)
326{ 289{
327 anfds [fd].events = 0; 290 anfds [fd].events = 0;
328 linuxaio_iocbps [fd]->io.aio_buf = 0; 291 linuxaio_iocbps [fd]->io.aio_buf = 0;
329 fd_change (EV_A_ fd, EV_ANFD_REIFY); 292 fd_change (EV_A_ fd, EV_ANFD_REIFY);
… …
345 fd, 308 fd,
346 (res & (POLLOUT | POLLERR | POLLHUP) ? EV_WRITE : 0) 309 (res & (POLLOUT | POLLERR | POLLHUP) ? EV_WRITE : 0)
347 | (res & (POLLIN | POLLERR | POLLHUP) ? EV_READ : 0) 310 | (res & (POLLIN | POLLERR | POLLHUP) ? EV_READ : 0)
348 ); 311 );
349 312
350 /* linux aio is oneshot: rearm fd. TODO: this does more work than needed */ 313 /* linux aio is oneshot: rearm fd. TODO: this does more work than strictly needed */
351 linuxaio_fd_rearm (EV_A_ fd); 314 linuxaio_fd_rearm (EV_A_ fd);
352 315
353 --nr; 316 --nr;
354 ++ev; 317 ++ev;
355 } 318 }
… …
368 unsigned tail = *(volatile unsigned *)&ring->tail; 331 unsigned tail = *(volatile unsigned *)&ring->tail;
369 332
370 if (head == tail) 333 if (head == tail)
371 return 0; 334 return 0;
372 335
373 /* bail out if the ring buffer doesn't match the expected layout */
374 if (expect_false (ring->magic != AIO_RING_MAGIC)
375 || ring->incompat_features != AIO_RING_INCOMPAT_FEATURES
376 || ring->header_length != sizeof (struct aio_ring)) /* TODO: or use it to find io_event[0]? */
377 return 0;
378
379 /* make sure the events up to tail are visible */ 336 /* make sure the events up to tail are visible */
380 ECB_MEMORY_FENCE_ACQUIRE; 337 ECB_MEMORY_FENCE_ACQUIRE;
381 338
382 /* parse all available events, but only once, to avoid starvation */ 339 /* parse all available events, but only once, to avoid starvation */
383 if (tail > head) /* normal case around */ 340 if (tail > head) /* normal case around */
… …
393 *(volatile unsigned *)&ring->head = tail; 350 *(volatile unsigned *)&ring->head = tail;
394 351
395 return 1; 352 return 1;
396} 353}
397 354
355inline_size
356int
357linuxaio_ringbuf_valid (EV_P)
358{
359 struct aio_ring *ring = (struct aio_ring *)linuxaio_ctx;
360
361 return ecb_expect_true (ring->magic == AIO_RING_MAGIC)
362 && ring->incompat_features == EV_AIO_RING_INCOMPAT_FEATURES
363 && ring->header_length == sizeof (struct aio_ring); /* TODO: or use it to find io_event[0]? */
364}
365
398/* read at least one event from kernel, or timeout */ 366/* read at least one event from kernel, or timeout */
399inline_size 367inline_size
400void 368void
401linuxaio_get_events (EV_P_ ev_tstamp timeout) 369linuxaio_get_events (EV_P_ ev_tstamp timeout)
402{ 370{
403 struct timespec ts; 371 struct timespec ts;
404 struct io_event ioev[1]; 372 struct io_event ioev[8]; /* 256 octet stack space */
405 int res; 373 int want = 1; /* how many events to request */
374 int ringbuf_valid = linuxaio_ringbuf_valid (EV_A);
406 375
376 if (ecb_expect_true (ringbuf_valid))
377 {
378 /* if the ring buffer has any events, we don't wait or call the kernel at all */
407 if (linuxaio_get_events_from_ring (EV_A)) 379 if (linuxaio_get_events_from_ring (EV_A))
408 return; 380 return;
409 381
410 /* no events, so wait for at least one, then poll ring buffer again */ 382 /* if the ring buffer is empty, and we don't have a timeout, then don't call the kernel */
411 /* this degrades to one event per loop iteration */ 383 if (!timeout)
412 /* if the ring buffer changes layout, but so be it */ 384 return;
385 }
386 else
387 /* no ringbuffer, request slightly larger batch */
388 want = sizeof (ioev) / sizeof (ioev [0]);
413 389
390 /* no events, so wait for some
391 * for fairness reasons, we do this in a loop, to fetch all events
392 */
393 for (;;)
394 {
395 int res;
396
414 EV_RELEASE_CB; 397 EV_RELEASE_CB;
415 398
416 ts.tv_sec = (long)timeout; 399 ts.tv_sec = (long)timeout;
417 ts.tv_nsec = (long)((timeout - ts.tv_sec) * 1e9); 400 ts.tv_nsec = (long)((timeout - ts.tv_sec) * 1e9);
418 401
419 res = evsys_io_getevents (linuxaio_ctx, 1, sizeof (ioev) / sizeof (ioev [0]), ioev, &ts); 402 res = evsys_io_getevents (linuxaio_ctx, 1, want, ioev, &ts);
420 403
421 EV_ACQUIRE_CB; 404 EV_ACQUIRE_CB;
422 405
423 if (res < 0) 406 if (res < 0)
424 if (errno == EINTR) 407 if (errno == EINTR)
425 /* ignored */; 408 /* ignored, retry */;
426 else 409 else
427 ev_syserr ("(libev) linuxaio io_getevents"); 410 ev_syserr ("(libev) linuxaio io_getevents");
428 else if (res) 411 else if (res)
429 { 412 {
430 /* at least one event available, handle it and any remaining ones in the ring buffer */ 413 /* at least one event available, handle them */
431 linuxaio_parse_events (EV_A_ ioev, res); 414 linuxaio_parse_events (EV_A_ ioev, res);
415
416 if (ecb_expect_true (ringbuf_valid))
417 {
418 /* if we have a ring buffer, handle any remaining events in it */
432 linuxaio_get_events_from_ring (EV_A); 419 linuxaio_get_events_from_ring (EV_A);
420
421 /* at this point, we should have handled all outstanding events */
422 break;
423 }
424 else if (res < want)
425 /* otherwise, if there were fewere events than we wanted, we assume there are no more */
426 break;
427 }
428 else
429 break; /* no events from the kernel, we are done */
430
431 timeout = 0; /* only wait in the first iteration */
433 } 432 }
434} 433}
435 434
436inline_size 435inline_size
437int 436int
… …
453 /* which allows us to pinpoint the erroneous iocb */ 452 /* which allows us to pinpoint the erroneous iocb */
454 for (submitted = 0; submitted < linuxaio_submitcnt; ) 453 for (submitted = 0; submitted < linuxaio_submitcnt; )
455 { 454 {
456 int res = evsys_io_submit (linuxaio_ctx, linuxaio_submitcnt - submitted, linuxaio_submits + submitted); 455 int res = evsys_io_submit (linuxaio_ctx, linuxaio_submitcnt - submitted, linuxaio_submits + submitted);
457 456
458 if (expect_false (res < 0)) 457 if (ecb_expect_false (res < 0))
459 if (errno == EINVAL) 458 if (errno == EINVAL)
460 { 459 {
461 /* This happens for unsupported fds, officially, but in my testing, 460 /* This happens for unsupported fds, officially, but in my testing,
462 * also randomly happens for supported fds. We fall back to good old 461 * also randomly happens for supported fds. We fall back to good old
463 * poll() here, under the assumption that this is a very rare case. 462 * poll() here, under the assumption that this is a very rare case.
… …
508 /* it's easiest to handle this mess in another iteration */ 507 /* it's easiest to handle this mess in another iteration */
509 return; 508 return;
510 } 509 }
511 else if (errno == EBADF) 510 else if (errno == EBADF)
512 { 511 {
512 assert (("libev: event loop rejected bad fd", errno != EBADF));
513 fd_kill (EV_A_ linuxaio_submits [submitted]->aio_fildes); 513 fd_kill (EV_A_ linuxaio_submits [submitted]->aio_fildes);
514 514
515 res = 1; /* skip this iocb */ 515 res = 1; /* skip this iocb */
516 } 516 }
517 else if (errno == EINTR) /* not seen in reality, not documented */
518 res = 0; /* silently ignore and retry */
517 else 519 else
518 ev_syserr ("(libev) linuxaio io_submit"); 520 ev_syserr ("(libev) linuxaio io_submit");
519 521
520 submitted += res; 522 submitted += res;
521 } 523 }
… …
570void 572void
571linuxaio_destroy (EV_P) 573linuxaio_destroy (EV_P)
572{ 574{
573 epoll_destroy (EV_A); 575 epoll_destroy (EV_A);
574 linuxaio_free_iocbp (EV_A); 576 linuxaio_free_iocbp (EV_A);
575 evsys_io_destroy (linuxaio_ctx); 577 evsys_io_destroy (linuxaio_ctx); /* fails in child, aio context is destroyed */
576} 578}
577 579
578inline_size 580inline_size
579void 581void
580linuxaio_fork (EV_P) 582linuxaio_fork (EV_P)
… …
586 linuxaio_iteration = 0; /* we start over in the child */ 588 linuxaio_iteration = 0; /* we start over in the child */
587 589
588 while (linuxaio_io_setup (EV_A) < 0) 590 while (linuxaio_io_setup (EV_A) < 0)
589 ev_syserr ("(libev) linuxaio io_setup"); 591 ev_syserr ("(libev) linuxaio io_setup");
590 592
593 /* forking epoll should also effectively unregister all fds from the backend */
591 epoll_fork (EV_A); 594 epoll_fork (EV_A);
592 595
593 ev_io_stop (EV_A_ &linuxaio_epoll_w); 596 ev_io_stop (EV_A_ &linuxaio_epoll_w);
594 ev_io_set (EV_A_ &linuxaio_epoll_w, backend_fd, EV_READ); 597 ev_io_set (EV_A_ &linuxaio_epoll_w, backend_fd, EV_READ);
595 ev_io_start (EV_A_ &linuxaio_epoll_w); 598 ev_io_start (EV_A_ &linuxaio_epoll_w);

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