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Revision 1.1 by root, Thu Jun 20 22:44:59 2019 UTC vs.
Revision 1.45 by root, Thu Jul 4 23:59:36 2019 UTC

… …
35 * and other provisions required by the GPL. If you do not delete the 35 * and other provisions required by the GPL. If you do not delete the
36 * provisions above, a recipient may use your version of this file under 36 * provisions above, a recipient may use your version of this file under
37 * either the BSD or the GPL. 37 * either the BSD or the GPL.
38 */ 38 */
39 39
40/*
41 * general notes about linux aio:
42 *
43 * a) at first, the linux aio IOCB_CMD_POLL functionality introduced in
44 * 4.18 looks too good to be true: both watchers and events can be
45 * batched, and events can even be handled in userspace using
46 * a ring buffer shared with the kernel. watchers can be canceled
47 * regardless of whether the fd has been closed. no problems with fork.
48 * ok, the ring buffer is 200% undocumented (there isn't even a
49 * header file), but otherwise, it's pure bliss!
50 * b) ok, watchers are one-shot, so you have to re-arm active ones
51 * on every iteration. so much for syscall-less event handling,
52 * but at least these re-arms can be batched, no big deal, right?
53 * c) well, linux as usual: the documentation lies to you: io_submit
54 * sometimes returns EINVAL because the kernel doesn't feel like
55 * handling your poll mask - ttys can be polled for POLLOUT,
56 * POLLOUT|POLLIN, but polling for POLLIN fails. just great,
57 * so we have to fall back to something else (hello, epoll),
58 * but at least the fallback can be slow, because these are
59 * exceptional cases, right?
60 * d) hmm, you have to tell the kernel the maximum number of watchers
61 * you want to queue when initialising the aio context. but of
62 * course the real limit is magically calculated in the kernel, and
63 * is often higher then we asked for. so we just have to destroy
64 * the aio context and re-create it a bit larger if we hit the limit.
65 * (starts to remind you of epoll? well, it's a bit more deterministic
66 * and less gambling, but still ugly as hell).
67 * e) that's when you find out you can also hit an arbitrary system-wide
68 * limit. or the kernel simply doesn't want to handle your watchers.
69 * what the fuck do we do then? you guessed it, in the middle
70 * of event handling we have to switch to 100% epoll polling. and
71 * that better is as fast as normal epoll polling, so you practically
72 * have to use the normal epoll backend with all its quirks.
73 * f) end result of this train wreck: it inherits all the disadvantages
74 * from epoll, while adding a number on its own. why even bother to use
75 * it? because if conditions are right and your fds are supported and you
76 * don't hit a limit, this backend is actually faster, doesn't gamble with
77 * your fds, batches watchers and events and doesn't require costly state
78 * recreates. well, until it does.
79 * g) all of this makes this backend use almost twice as much code as epoll.
80 * which in turn uses twice as much code as poll. and that#s not counting
81 * the fact that this backend also depends on the epoll backend, making
82 * it three times as much code as poll, or kqueue.
83 * h) bleah. why can't linux just do kqueue. sure kqueue is ugly, but by now
84 * it's clear that whatever linux comes up with is far, far, far worse.
85 */
86
40#include <sys/time.h> /* actually linux/time.h, but we must assume they are compatible */ 87#include <sys/time.h> /* actually linux/time.h, but we must assume they are compatible */
88#include <poll.h>
41#include <linux/aio_abi.h> 89#include <linux/aio_abi.h>
42 90
43/* we try to fill 4kn pages exactly. 91/*****************************************************************************/
44 * the ring buffer header is 32 bytes, every io event is 32 bytes. 92/* syscall wrapdadoop - this section has the raw api/abi definitions */
45 * the kernel takes the io event number, doubles it, adds 2, adds the ring buffer 93
46 * so the calculation below will use "exactly" 8kB for the ring buffer 94#include <sys/syscall.h> /* no glibc wrappers */
95
96/* aio_abi.h is not versioned in any way, so we cannot test for its existance */
97#define IOCB_CMD_POLL 5
98
99/* taken from linux/fs/aio.c. yup, that's a .c file.
100 * not only is this totally undocumented, not even the source code
101 * can tell you what the future semantics of compat_features and
102 * incompat_features are, or what header_length actually is for.
47 */ 103 */
48#define EV_LINUXAIO_DEPTH (256 / 2 - 2 - 1) /* max. number of io events per batch */
49
50/*****************************************************************************/
51/* syscall wrapdadoop */
52
53#include <sys/syscall.h> /* no glibc wrappers */
54
55/* aio_abi.h is not verioned in any way, so we cannot test for its existance */
56#define IOCB_CMD_POLL 5
57
58/* taken from linux/fs/aio.c */
59#define AIO_RING_MAGIC 0xa10a10a1 104#define AIO_RING_MAGIC 0xa10a10a1
60#define AIO_RING_INCOMPAT_FEATURES 0 105#define EV_AIO_RING_INCOMPAT_FEATURES 0
61struct aio_ring 106struct aio_ring
62{ 107{
63 unsigned id; /* kernel internal index number */ 108 unsigned id; /* kernel internal index number */
64 unsigned nr; /* number of io_events */ 109 unsigned nr; /* number of io_events */
65 unsigned head; /* Written to by userland or by kernel. */ 110 unsigned head; /* Written to by userland or by kernel. */
… …
71 unsigned header_length; /* size of aio_ring */ 116 unsigned header_length; /* size of aio_ring */
72 117
73 struct io_event io_events[0]; 118 struct io_event io_events[0];
74}; 119};
75 120
76static int 121inline_size
122int
77ev_io_setup (unsigned nr_events, aio_context_t *ctx_idp) 123evsys_io_setup (unsigned nr_events, aio_context_t *ctx_idp)
78{ 124{
79 return syscall (SYS_io_setup, nr_events, ctx_idp); 125 return ev_syscall2 (SYS_io_setup, nr_events, ctx_idp);
80} 126}
81 127
82static int 128inline_size
129int
83ev_io_destroy (aio_context_t ctx_id) 130evsys_io_destroy (aio_context_t ctx_id)
84{ 131{
85 return syscall (SYS_io_destroy, ctx_id); 132 return ev_syscall1 (SYS_io_destroy, ctx_id);
86} 133}
87 134
88static int 135inline_size
136int
89ev_io_submit (aio_context_t ctx_id, long nr, struct iocb *cbp[]) 137evsys_io_submit (aio_context_t ctx_id, long nr, struct iocb *cbp[])
90{ 138{
91 return syscall (SYS_io_submit, ctx_id, nr, cbp); 139 return ev_syscall3 (SYS_io_submit, ctx_id, nr, cbp);
92} 140}
93 141
94static int 142inline_size
143int
95ev_io_cancel (aio_context_t ctx_id, struct iocb *cbp, struct io_event *result) 144evsys_io_cancel (aio_context_t ctx_id, struct iocb *cbp, struct io_event *result)
96{ 145{
97 return syscall (SYS_io_cancel, ctx_id, cbp, result); 146 return ev_syscall3 (SYS_io_cancel, ctx_id, cbp, result);
98} 147}
99 148
100static int 149inline_size
150int
101ev_io_getevents (aio_context_t ctx_id, long min_nr, long nr, struct io_event *events, struct timespec *timeout) 151evsys_io_getevents (aio_context_t ctx_id, long min_nr, long nr, struct io_event *events, struct timespec *timeout)
102{ 152{
103 return syscall (SYS_io_getevents, ctx_id, min_nr, nr, events, timeout); 153 return ev_syscall5 (SYS_io_getevents, ctx_id, min_nr, nr, events, timeout);
104} 154}
105
106typedef void (*ev_io_cb) (long nr, struct io_event *events);
107 155
108/*****************************************************************************/ 156/*****************************************************************************/
109/* actual backed implementation */ 157/* actual backed implementation */
110 158
111/* two iocbs for every fd, one for read, one for write */ 159ecb_cold
160static int
161linuxaio_nr_events (EV_P)
162{
163 /* we start with 16 iocbs and incraese from there
164 * that's tiny, but the kernel has a rather low system-wide
165 * limit that can be reached quickly, so let's be parsimonious
166 * with this resource.
167 * Rest assured, the kernel generously rounds up small and big numbers
168 * in different ways (but doesn't seem to charge you for it).
169 * The 15 here is because the kernel usually has a power of two as aio-max-nr,
170 * and this helps to take advantage of that limit.
171 */
172
173 /* we try to fill 4kB pages exactly.
174 * the ring buffer header is 32 bytes, every io event is 32 bytes.
175 * the kernel takes the io requests number, doubles it, adds 2
176 * and adds the ring buffer.
177 * the way we use this is by starting low, and then roughly doubling the
178 * size each time we hit a limit.
179 */
180
181 int requests = 15 << linuxaio_iteration;
182 int one_page = (4096
183 / sizeof (struct io_event) ) / 2; /* how many fit into one page */
184 int first_page = ((4096 - sizeof (struct aio_ring))
185 / sizeof (struct io_event) - 2) / 2; /* how many fit into the first page */
186
187 /* if everything fits into one page, use count exactly */
188 if (requests > first_page)
189 /* otherwise, round down to full pages and add the first page */
190 requests = requests / one_page * one_page + first_page;
191
192 return requests;
193}
194
195/* we use out own wrapper structure in case we ever want to do something "clever" */
112typedef struct aniocb 196typedef struct aniocb
113{ 197{
114 struct iocb io; 198 struct iocb io;
115 /*int inuse;*/ 199 /*int inuse;*/
116} *ANIOCBP; 200} *ANIOCBP;
117 201
118inline_size 202inline_size
119void 203void
120linuxaio_array_needsize_iocbp (ANIOCBP *base, int count) 204linuxaio_array_needsize_iocbp (ANIOCBP *base, int offset, int count)
121{ 205{
122 /* TODO: quite the overhead to allocate every iocb separately */
123 while (count--) 206 while (count--)
124 { 207 {
208 /* TODO: quite the overhead to allocate every iocb separately, maybe use our own allocator? */
125 *base = (ANIOCBP)ev_malloc (sizeof (**base)); 209 ANIOCBP iocb = (ANIOCBP)ev_malloc (sizeof (*iocb));
210
211 /* full zero initialise is probably not required at the moment, but
212 * this is not well documented, so we better do it.
213 */
126 memset (*base, 0, sizeof (**base)); 214 memset (iocb, 0, sizeof (*iocb));
127 /* would be nice to initialize fd/data as well */ 215
128 (*base)->io.aio_lio_opcode = IOCB_CMD_POLL; 216 iocb->io.aio_lio_opcode = IOCB_CMD_POLL;
129 ++base; 217 iocb->io.aio_data = offset;
130 } 218 iocb->io.aio_fildes = offset;
131}
132 219
220 base [offset++] = iocb;
221 }
222}
223
224ecb_cold
133static void 225static void
134linuxaio_free_iocbp (EV_P) 226linuxaio_free_iocbp (EV_P)
135{ 227{
136 while (linuxaio_iocbpmax--) 228 while (linuxaio_iocbpmax--)
137 ev_free (linuxaio_iocbps [linuxaio_iocbpmax]); 229 ev_free (linuxaio_iocbps [linuxaio_iocbpmax]);
138 230
139 linuxaio_iocbpmax = 0; 231 linuxaio_iocbpmax = 0; /* next resize will completely reallocate the array, at some overhead */
140} 232}
141 233
142static void 234static void
143linuxaio_modify (EV_P_ int fd, int oev, int nev) 235linuxaio_modify (EV_P_ int fd, int oev, int nev)
144{ 236{
145 /* TODO: full zero initialize required? */
146 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);
147 struct aniocb *iocb = linuxaio_iocbps [fd]; 238 ANIOCBP iocb = linuxaio_iocbps [fd];
148 239
240 if (ecb_expect_false (iocb->io.aio_reqprio < 0))
241 {
242 /* we handed this fd over to epoll, so undo this first */
243 /* we do it manually because the optimisations on epoll_modify won't do us any good */
244 epoll_ctl (backend_fd, EPOLL_CTL_DEL, fd, 0);
245 anfds [fd].emask = 0;
246 iocb->io.aio_reqprio = 0;
247 }
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
149 if (iocb->io.aio_buf) 266 iocb->io.aio_buf =
150 ev_io_cancel (linuxaio_ctx, &iocb->io, (void *)0); 267 (nev & EV_READ ? POLLIN : 0)
268 | (nev & EV_WRITE ? POLLOUT : 0);
151 269
152 if (nev) 270 if (nev)
153 { 271 {
154 iocb->io.aio_data = fd;
155 iocb->io.aio_fildes = fd;
156 iocb->io.aio_buf =
157 (nev & EV_READ ? POLLIN : 0)
158 | (nev & EV_WRITE ? POLLOUT : 0);
159
160 /* queue iocb up for io_submit */ 272 /* queue iocb up for io_submit */
161 /* 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 */
162 ++linuxaio_submitcnt; 274 ++linuxaio_submitcnt;
163 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);
164 linuxaio_submits [linuxaio_submitcnt - 1] = &iocb->io; 276 linuxaio_submits [linuxaio_submitcnt - 1] = &iocb->io;
165 } 277 }
166} 278}
167 279
168static void 280static void
281linuxaio_epoll_cb (EV_P_ struct ev_io *w, int revents)
282{
283 epoll_poll (EV_A_ 0);
284}
285
286inline_speed
287void
288linuxaio_fd_rearm (EV_P_ int fd)
289{
290 anfds [fd].events = 0;
291 linuxaio_iocbps [fd]->io.aio_buf = 0;
292 fd_change (EV_A_ fd, EV_ANFD_REIFY);
293}
294
295static void
169linuxaio_parse_events (EV_P_ struct io_event *ev, int nr) 296linuxaio_parse_events (EV_P_ struct io_event *ev, int nr)
170{ 297{
171 while (nr) 298 while (nr)
172 { 299 {
173 int fd = ev->data; 300 int fd = ev->data;
174 int res = ev->res; 301 int res = ev->res;
175 302
176 assert (("libev: iocb fd must be in-bounds", fd >= 0 && fd < anfdxmax)); 303 assert (("libev: iocb fd must be in-bounds", fd >= 0 && fd < anfdmax));
177
178 /* linux aio is oneshot: rearm fd */
179 linuxaio_iocbps [fd]->io.aio_buf = 0;
180 anfds [fd].events = 0;
181 fd_change (EV_A_ fd, 0);
182 304
183 /* feed events, we do not expect or handle POLLNVAL */ 305 /* feed events, we do not expect or handle POLLNVAL */
184 if (ecb_expect_false (res & POLLNVAL))
185 fd_kill (EV_A_ fd);
186 else
187 fd_event ( 306 fd_event (
188 EV_A_ 307 EV_A_
189 fd, 308 fd,
190 (res & (POLLOUT | POLLERR | POLLHUP) ? EV_WRITE : 0) 309 (res & (POLLOUT | POLLERR | POLLHUP) ? EV_WRITE : 0)
191 | (res & (POLLIN | POLLERR | POLLHUP) ? EV_READ : 0) 310 | (res & (POLLIN | POLLERR | POLLHUP) ? EV_READ : 0)
192 ); 311 );
312
313 /* linux aio is oneshot: rearm fd. TODO: this does more work than strictly needed */
314 linuxaio_fd_rearm (EV_A_ fd);
193 315
194 --nr; 316 --nr;
195 ++ev; 317 ++ev;
196 } 318 }
197} 319}
198 320
199/* get any events from ringbuffer, return true if any were handled */ 321/* get any events from ring buffer, return true if any were handled */
200static int 322static int
201linuxaio_get_events_from_ring (EV_P) 323linuxaio_get_events_from_ring (EV_P)
202{ 324{
203 struct aio_ring *ring = (struct aio_ring *)linuxaio_ctx; 325 struct aio_ring *ring = (struct aio_ring *)linuxaio_ctx;
326 unsigned head, tail;
204 327
328 /* the kernel reads and writes both of these variables, */
329 /* as a C extension, we assume that volatile use here */
330 /* both makes reads atomic and once-only */
331 head = *(volatile unsigned *)&ring->head;
205 ECB_MEMORY_FENCE_ACQUIRE; 332 ECB_MEMORY_FENCE_ACQUIRE;
206
207 unsigned head = ring->head;
208 unsigned tail = *(volatile unsigned *)&ring->tail; 333 tail = *(volatile unsigned *)&ring->tail;
209 334
210 if (ring->magic != AIO_RING_MAGIC 335 if (head == tail)
211 || ring->incompat_features != AIO_RING_INCOMPAT_FEATURES
212 || ring->header_length != sizeof (struct aio_ring) /* TODO: or use it to find io_event[0]? */
213 || head == tail)
214 return 0; 336 return 0;
215 337
216 /* parse all available events, but only once, to avoid starvation */ 338 /* parse all available events, but only once, to avoid starvation */
217 if (tail > head) /* normal case around */ 339 if (ecb_expect_true (tail > head)) /* normal case around */
218 linuxaio_parse_events (EV_A_ ring->io_events + head, tail - head); 340 linuxaio_parse_events (EV_A_ ring->io_events + head, tail - head);
219 else
220 {
221 /* wrapped around */ 341 else /* wrapped around */
342 {
222 linuxaio_parse_events (EV_A_ ring->io_events + head, ring->nr - head); 343 linuxaio_parse_events (EV_A_ ring->io_events + head, ring->nr - head);
223 linuxaio_parse_events (EV_A_ ring->io_events, tail); 344 linuxaio_parse_events (EV_A_ ring->io_events, tail);
224 } 345 }
225 346
226 ring->head = tail; 347 ECB_MEMORY_FENCE_RELEASE;
348 /* as an extension to C, we hope that the volatile will make this atomic and once-only */
349 *(volatile unsigned *)&ring->head = tail;
227 350
228 return 1; 351 return 1;
352}
353
354inline_size
355int
356linuxaio_ringbuf_valid (EV_P)
357{
358 struct aio_ring *ring = (struct aio_ring *)linuxaio_ctx;
359
360 return ecb_expect_true (ring->magic == AIO_RING_MAGIC)
361 && ring->incompat_features == EV_AIO_RING_INCOMPAT_FEATURES
362 && ring->header_length == sizeof (struct aio_ring); /* TODO: or use it to find io_event[0]? */
229} 363}
230 364
231/* read at least one event from kernel, or timeout */ 365/* read at least one event from kernel, or timeout */
232inline_size 366inline_size
233void 367void
234linuxaio_get_events (EV_P_ ev_tstamp timeout) 368linuxaio_get_events (EV_P_ ev_tstamp timeout)
235{ 369{
236 struct timespec ts; 370 struct timespec ts;
237 struct io_event ioev; 371 struct io_event ioev[8]; /* 256 octet stack space */
238 int res; 372 int want = 1; /* how many events to request */
373 int ringbuf_valid = linuxaio_ringbuf_valid (EV_A);
239 374
375 if (ecb_expect_true (ringbuf_valid))
376 {
377 /* if the ring buffer has any events, we don't wait or call the kernel at all */
240 if (linuxaio_get_events_from_ring (EV_A)) 378 if (linuxaio_get_events_from_ring (EV_A))
241 return; 379 return;
242 380
243 /* no events, so wait for at least one, then poll ring buffer again */ 381 /* if the ring buffer is empty, and we don't have a timeout, then don't call the kernel */
244 /* this degraded to one event per loop iteration */ 382 if (!timeout)
245 /* if the ring buffer changes layout, but so be it */ 383 return;
384 }
385 else
386 /* no ringbuffer, request slightly larger batch */
387 want = sizeof (ioev) / sizeof (ioev [0]);
246 388
247 ts.tv_sec = (long)timeout; 389 /* no events, so wait for some
248 ts.tv_nsec = (long)((timeout - ts.tv_sec) * 1e9); 390 * for fairness reasons, we do this in a loop, to fetch all events
391 */
392 for (;;)
393 {
394 int res;
249 395
396 EV_RELEASE_CB;
397
398 EV_TS_SET (ts, timeout);
250 res = ev_io_getevents (linuxaio_ctx, 1, 1, &ioev, &ts); 399 res = evsys_io_getevents (linuxaio_ctx, 1, want, ioev, &ts);
251 400
401 EV_ACQUIRE_CB;
402
252 if (res < 0) 403 if (res < 0)
404 if (errno == EINTR)
405 /* ignored, retry */;
406 else
253 ev_syserr ("(libev) io_getevents"); 407 ev_syserr ("(libev) linuxaio io_getevents");
254 else if (res) 408 else if (res)
255 { 409 {
256 /* at least one event received, handle it and any remaining ones in the ring buffer */ 410 /* at least one event available, handle them */
257 linuxaio_parse_events (EV_A_ &ioev, 1); 411 linuxaio_parse_events (EV_A_ ioev, res);
412
413 if (ecb_expect_true (ringbuf_valid))
414 {
415 /* if we have a ring buffer, handle any remaining events in it */
258 linuxaio_get_events_from_ring (EV_A); 416 linuxaio_get_events_from_ring (EV_A);
417
418 /* at this point, we should have handled all outstanding events */
419 break;
420 }
421 else if (res < want)
422 /* otherwise, if there were fewere events than we wanted, we assume there are no more */
423 break;
424 }
425 else
426 break; /* no events from the kernel, we are done */
427
428 timeout = 0; /* only wait in the first iteration */
259 } 429 }
430}
431
432inline_size
433int
434linuxaio_io_setup (EV_P)
435{
436 linuxaio_ctx = 0;
437 return evsys_io_setup (linuxaio_nr_events (EV_A), &linuxaio_ctx);
260} 438}
261 439
262static void 440static void
263linuxaio_poll (EV_P_ ev_tstamp timeout) 441linuxaio_poll (EV_P_ ev_tstamp timeout)
264{ 442{
… …
266 444
267 /* first phase: submit new iocbs */ 445 /* first phase: submit new iocbs */
268 446
269 /* io_submit might return less than the requested number of iocbs */ 447 /* io_submit might return less than the requested number of iocbs */
270 /* this is, afaics, only because of errors, but we go by the book and use a loop, */ 448 /* this is, afaics, only because of errors, but we go by the book and use a loop, */
271 /* which allows us to pinpoint the errornous iocb */ 449 /* which allows us to pinpoint the erroneous iocb */
272 for (submitted = 0; submitted < linuxaio_submitcnt; ) 450 for (submitted = 0; submitted < linuxaio_submitcnt; )
273 { 451 {
274 int res = ev_io_submit (linuxaio_ctx, linuxaio_submitcnt - submitted, linuxaio_submits + submitted); 452 int res = evsys_io_submit (linuxaio_ctx, linuxaio_submitcnt - submitted, linuxaio_submits + submitted);
275 453
276 if (res < 0) 454 if (ecb_expect_false (res < 0))
277 if (errno == EAGAIN) 455 if (errno == EINVAL)
278 { 456 {
279 /* This happens when the ring buffer is full, at least. I assume this means 457 /* This happens for unsupported fds, officially, but in my testing,
280 * that the event was queued synchronously during io_submit, and thus 458 * also randomly happens for supported fds. We fall back to good old
281 * the buffer overflowd. 459 * poll() here, under the assumption that this is a very rare case.
282 * In this case, we just try next loop iteration. 460 * See https://lore.kernel.org/patchwork/patch/1047453/ to see
461 * discussion about such a case (ttys) where polling for POLLIN
462 * fails but POLLIN|POLLOUT works.
283 */ 463 */
284 memcpy (linuxaio_submits, linuxaio_submits + submitted, (linuxaio_submitcnt - submitted) * sizeof (*linuxaio_submits)); 464 struct iocb *iocb = linuxaio_submits [submitted];
465 epoll_modify (EV_A_ iocb->aio_fildes, 0, anfds [iocb->aio_fildes].events);
466 iocb->aio_reqprio = -1; /* mark iocb as epoll */
467
468 res = 1; /* skip this iocb - another iocb, another chance */
469 }
470 else if (errno == EAGAIN)
471 {
472 /* This happens when the ring buffer is full, or some other shit we
473 * don't know and isn't documented. Most likely because we have too
474 * many requests and linux aio can't be assed to handle them.
475 * In this case, we try to allocate a larger ring buffer, freeing
476 * ours first. This might fail, in which case we have to fall back to 100%
477 * epoll.
478 * God, how I hate linux not getting its act together. Ever.
479 */
480 evsys_io_destroy (linuxaio_ctx);
285 linuxaio_submitcnt -= submitted; 481 linuxaio_submitcnt = 0;
482
483 /* rearm all fds with active iocbs */
484 {
485 int fd;
486 for (fd = 0; fd < linuxaio_iocbpmax; ++fd)
487 if (linuxaio_iocbps [fd]->io.aio_buf)
488 linuxaio_fd_rearm (EV_A_ fd);
489 }
490
491 ++linuxaio_iteration;
492 if (linuxaio_io_setup (EV_A) < 0)
493 {
494 /* TODO: rearm all and recreate epoll backend from scratch */
495 /* TODO: might be more prudent? */
496
497 /* to bad, we can't get a new aio context, go 100% epoll */
498 linuxaio_free_iocbp (EV_A);
499 ev_io_stop (EV_A_ &linuxaio_epoll_w);
500 ev_ref (EV_A);
501 linuxaio_ctx = 0;
502
503 backend = EVBACKEND_EPOLL;
504 backend_modify = epoll_modify;
505 backend_poll = epoll_poll;
506 }
507
286 timeout = 0; 508 timeout = 0;
509 /* it's easiest to handle this mess in another iteration */
287 break; 510 return;
288 } 511 }
512 else if (errno == EBADF)
513 {
514 assert (("libev: event loop rejected bad fd", errno != EBADF));
515 fd_kill (EV_A_ linuxaio_submits [submitted]->aio_fildes);
516
517 res = 1; /* skip this iocb */
518 }
519 else if (errno == EINTR) /* not seen in reality, not documented */
520 res = 0; /* silently ignore and retry */
289 else 521 else
290 /* TODO: we get EAGAIN when the ring buffer is full for some reason */ 522 {
291 /* TODO: should we always just try next time? */
292 ev_syserr ("(libev) io_submit"); 523 ev_syserr ("(libev) linuxaio io_submit");
524 res = 0;
525 }
293 526
294 submitted += res; 527 submitted += res;
295 } 528 }
296 529
297 linuxaio_submitcnt = 0; 530 linuxaio_submitcnt = 0;
… …
304inline_size 537inline_size
305int 538int
306linuxaio_init (EV_P_ int flags) 539linuxaio_init (EV_P_ int flags)
307{ 540{
308 /* would be great to have a nice test for IOCB_CMD_POLL instead */ 541 /* would be great to have a nice test for IOCB_CMD_POLL instead */
309 if (ev_linux_version () < 0x041200) /* 4.18 introduced IOCB_CMD_POLL */ 542 /* also: test some semi-common fd types, such as files and ttys in recommended_backends */
543 /* 4.18 introduced IOCB_CMD_POLL, 4.19 made epoll work, and we need that */
544 if (ev_linux_version () < 0x041300)
310 return 0; 545 return 0;
311 546
312 if (ev_io_setup (EV_LINUXAIO_DEPTH, &linuxaio_ctx) < 0) 547 if (!epoll_init (EV_A_ 0))
313 return 0; 548 return 0;
314 549
550 linuxaio_iteration = 0;
551
552 if (linuxaio_io_setup (EV_A) < 0)
553 {
554 epoll_destroy (EV_A);
555 return 0;
556 }
557
558 ev_io_init (EV_A_ &linuxaio_epoll_w, linuxaio_epoll_cb, backend_fd, EV_READ);
559 ev_set_priority (&linuxaio_epoll_w, EV_MAXPRI);
560 ev_io_start (EV_A_ &linuxaio_epoll_w);
561 ev_unref (EV_A); /* watcher should not keep loop alive */
562
315 backend_modify = linuxaio_modify; 563 backend_modify = linuxaio_modify;
316 backend_poll = linuxaio_poll; 564 backend_poll = linuxaio_poll;
317 565
318 linuxaio_iocbpmax = 0; 566 linuxaio_iocbpmax = 0;
319 linuxaio_iocbps = 0; 567 linuxaio_iocbps = 0;
320 568
321 linuxaio_submits = 0; 569 linuxaio_submits = 0;
… …
327 575
328inline_size 576inline_size
329void 577void
330linuxaio_destroy (EV_P) 578linuxaio_destroy (EV_P)
331{ 579{
580 epoll_destroy (EV_A);
332 linuxaio_free_iocbp (EV_A); 581 linuxaio_free_iocbp (EV_A);
333 ev_io_destroy (linuxaio_ctx); 582 evsys_io_destroy (linuxaio_ctx); /* fails in child, aio context is destroyed */
334} 583}
335 584
336inline_size 585ecb_cold
337void 586static void
338linuxaio_fork (EV_P) 587linuxaio_fork (EV_P)
339{ 588{
340 abort ();//D 589 /* this frees all iocbs, which is very heavy-handed */
341} 590 linuxaio_destroy (EV_A);
591 linuxaio_submitcnt = 0; /* all pointers were invalidated */
342 592
593 linuxaio_iteration = 0; /* we start over in the child */
594
595 while (linuxaio_io_setup (EV_A) < 0)
596 ev_syserr ("(libev) linuxaio io_setup");
597
598 /* forking epoll should also effectively unregister all fds from the backend */
599 epoll_fork (EV_A);
600 /* epoll_fork already did this. hopefully */
601 /*fd_rearm_all (EV_A);*/
602
603 ev_io_stop (EV_A_ &linuxaio_epoll_w);
604 ev_io_set (EV_A_ &linuxaio_epoll_w, backend_fd, EV_READ);
605 ev_io_start (EV_A_ &linuxaio_epoll_w);
606}
607

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