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Comparing libev/ev_iouring.c (file contents):
Revision 1.1 by root, Tue Jul 2 06:07:54 2019 UTC vs.
Revision 1.23 by root, Sun Jul 26 11:10:45 2020 UTC

1/* 1/*
2 * libev linux io_uring fd activity backend 2 * libev linux io_uring fd activity backend
3 * 3 *
4 * Copyright (c) 2019 Marc Alexander Lehmann <libev@schmorp.de> 4 * Copyright (c) 2019-2020 Marc Alexander Lehmann <libev@schmorp.de>
5 * All rights reserved. 5 * All rights reserved.
6 * 6 *
7 * Redistribution and use in source and binary forms, with or without modifica- 7 * Redistribution and use in source and binary forms, with or without modifica-
8 * tion, are permitted provided that the following conditions are met: 8 * tion, are permitted provided that the following conditions are met:
9 * 9 *
… …
44 * b) best is not necessarily very good. 44 * b) best is not necessarily very good.
45 * c) it's better than the aio mess, doesn't suffer from the fork problems 45 * c) it's better than the aio mess, doesn't suffer from the fork problems
46 * of linux aio or epoll and so on and so on. and you could do event stuff 46 * of linux aio or epoll and so on and so on. and you could do event stuff
47 * without any syscalls. what's not to like? 47 * without any syscalls. what's not to like?
48 * d) ok, it's vastly more complex, but that's ok, really. 48 * d) ok, it's vastly more complex, but that's ok, really.
49 * e) why 3 mmaps instead of one? one would be more space-efficient, 49 * e) why two mmaps instead of one? one would be more space-efficient,
50 * and I can't see what benefit three would have (other than being 50 * and I can't see what benefit two would have (other than being
51 * somehow resizable/relocatable, but that's apparently not possible). 51 * somehow resizable/relocatable, but that's apparently not possible).
52 * f) hmm, it's practiclaly undebuggable (gdb can't access the memory, and 52 * f) hmm, it's practically undebuggable (gdb can't access the memory, and
53 the bizarre way structure offsets are commuinicated makes it hard to 53 * the bizarre way structure offsets are communicated makes it hard to
54 * just print the ring buffer heads, even *iff* the memory were visible 54 * just print the ring buffer heads, even *iff* the memory were visible
55 * in gdb. but then, that's also ok, really. 55 * in gdb. but then, that's also ok, really.
56 * g) well, you cannot specify a timeout when waiting for events. no, 56 * g) well, you cannot specify a timeout when waiting for events. no,
57 * seriously, the interface doesn't support a timeout. never seen _that_ 57 * seriously, the interface doesn't support a timeout. never seen _that_
58 * before. sure, you can use a timerfd, but that's another syscall 58 * before. sure, you can use a timerfd, but that's another syscall
59 * you could have avoided. overall, this bizarre omission smells 59 * you could have avoided. overall, this bizarre omission smells
60 * like a µ-optimisation by the io_uring author for his personal 60 * like a µ-optimisation by the io_uring author for his personal
61 * applications, to the detriment of everybody else who just wants 61 * applications, to the detriment of everybody else who just wants
62 * an event loop. but, umm, ok, if that's all, it could be worse. 62 * an event loop. but, umm, ok, if that's all, it could be worse.
63 * (from what I gather from the author Jens Axboe, it simply didn't
64 * occur to him, and he made good on it by adding an unlimited number
65 * of timeouts later :).
63 * h) there is a hardcoded limit of 4096 outstanding events. okay, 66 * h) initially there was a hardcoded limit of 4096 outstanding events.
64 * at least there is no arbitrary low system-wide limit... 67 * later versions not only bump this to 32k, but also can handle
68 * an unlimited amount of events, so this only affects the batch size.
65 * i) unlike linux aio, you *can* register more then the limit 69 * i) unlike linux aio, you *can* register more then the limit
66 * of fd events, and the kernel will "gracefully" signal an 70 * of fd events. while early verisons of io_uring signalled an overflow
67 * overflow, after which you could destroy and recreate the kernel 71 * and you ended up getting wet. 5.5+ does not do this anymore.
68 * state, a bit bigger, or fall back to e.g. poll. thats not
69 * totally insane, but kind of questions the point a high
70 * performance I/O framework when it doesn't really work
71 * under stress.
72 * j) but, oh my! is has exactly the same bugs as the linux aio backend, 72 * j) but, oh my! it had exactly the same bugs as the linux aio backend,
73 * where some undocumented poll combinations just fail. 73 * where some undocumented poll combinations just fail. fortunately,
74 * so we need epoll AGAIN as a fallback. AGAIN! epoll!! and of course, 74 * after finally reaching the author, he was more than willing to fix
75 * this is completely undocumented, have I mantioned this already? 75 * this probably in 5.6+.
76 * k) overall, the *API* itself is, I dare to say, not a total trainwreck. 76 * k) overall, the *API* itself is, I dare to say, not a total trainwreck.
77 * the big isuess with it are the bugs requiring epoll, which might 77 * once the bugs ae fixed (probably in 5.6+), it will be without
78 * or might not get fixed (do I hold my breath?). 78 * competition.
79 */ 79 */
80
81/* TODO: use internal TIMEOUT */
82/* TODO: take advantage of single mmap, NODROP etc. */
83/* TODO: resize cq/sq size independently */
80 84
81#include <sys/timerfd.h> 85#include <sys/timerfd.h>
82#include <sys/mman.h> 86#include <sys/mman.h>
83#include <poll.h> 87#include <poll.h>
88#include <stdint.h>
84 89
85#define IOURING_INIT_ENTRIES 32 90#define IOURING_INIT_ENTRIES 32
86 91
87/*****************************************************************************/ 92/*****************************************************************************/
88/* syscall wrapdadoop - this section has the raw api/abi definitions */ 93/* syscall wrapdadoop - this section has the raw api/abi definitions */
… …
96{ 101{
97 __u8 opcode; 102 __u8 opcode;
98 __u8 flags; 103 __u8 flags;
99 __u16 ioprio; 104 __u16 ioprio;
100 __s32 fd; 105 __s32 fd;
106 union {
101 __u64 off; 107 __u64 off;
108 __u64 addr2;
109 };
102 __u64 addr; 110 __u64 addr;
103 __u32 len; 111 __u32 len;
104 union { 112 union {
105 __kernel_rwf_t rw_flags; 113 __kernel_rwf_t rw_flags;
106 __u32 fsync_flags; 114 __u32 fsync_flags;
107 __u16 poll_events; 115 __u16 poll_events;
108 __u32 sync_range_flags; 116 __u32 sync_range_flags;
109 __u32 msg_flags; 117 __u32 msg_flags;
118 __u32 timeout_flags;
119 __u32 accept_flags;
120 __u32 cancel_flags;
121 __u32 open_flags;
122 __u32 statx_flags;
123 __u32 fadvise_advice;
110 }; 124 };
111 __u64 user_data; 125 __u64 user_data;
112 union { 126 union {
113 __u16 buf_index; 127 __u16 buf_index;
128 __u16 personality;
114 __u64 __pad2[3]; 129 __u64 __pad2[3];
115 }; 130 };
116}; 131};
117 132
118struct io_uring_cqe 133struct io_uring_cqe
… …
151 __u32 sq_entries; 166 __u32 sq_entries;
152 __u32 cq_entries; 167 __u32 cq_entries;
153 __u32 flags; 168 __u32 flags;
154 __u32 sq_thread_cpu; 169 __u32 sq_thread_cpu;
155 __u32 sq_thread_idle; 170 __u32 sq_thread_idle;
171 __u32 features;
156 __u32 resv[5]; 172 __u32 resv[4];
157 struct io_sqring_offsets sq_off; 173 struct io_sqring_offsets sq_off;
158 struct io_cqring_offsets cq_off; 174 struct io_cqring_offsets cq_off;
159}; 175};
160 176
177#define IORING_FEAT_SINGLE_MMAP 0x00000001
178#define IORING_FEAT_NODROP 0x00000002
179#define IORING_FEAT_SUBMIT_STABLE 0x00000004
180
181#define IORING_SETUP_CQSIZE 0x00000008
182#define IORING_SETUP_CLAMP 0x00000010
183
161#define IORING_OP_POLL_ADD 6 184#define IORING_OP_POLL_ADD 6
162#define IORING_OP_POLL_REMOVE 7 185#define IORING_OP_POLL_REMOVE 7
186#define IORING_OP_TIMEOUT 11
187#define IORING_OP_TIMEOUT_REMOVE 12
188
189#define IORING_REGISTER_EVENTFD 4
190#define IORING_REGISTER_EVENTFD_ASYNC 7
191#define IORING_REGISTER_PROBE 8
192
193#define IO_URING_OP_SUPPORTED 1
194
195struct io_uring_probe_op {
196 __u8 op;
197 __u8 resv;
198 __u16 flags;
199 __u32 resv2;
200};
201
202struct io_uring_probe
203{
204 __u8 last_op;
205 __u8 ops_len;
206 __u16 resv;
207 __u32 resv2[3];
208 struct io_uring_probe_op ops[0];
209};
210
211/* relative or absolute, reference clock is CLOCK_MONOTONIC */
212struct iouring_kernel_timespec
213{
214 int64_t tv_sec;
215 long long tv_nsec;
216};
217
218#define IORING_TIMEOUT_ABS 0x00000001
163 219
164#define IORING_ENTER_GETEVENTS 0x01 220#define IORING_ENTER_GETEVENTS 0x01
165 221
166#define IORING_OFF_SQ_RING 0x00000000ULL 222#define IORING_OFF_SQ_RING 0x00000000ULL
167#define IORING_OFF_CQ_RING 0x08000000ULL
168#define IORING_OFF_SQES 0x10000000ULL 223#define IORING_OFF_SQES 0x10000000ULL
224
225#define IORING_FEAT_SINGLE_MMAP 0x00000001
226#define IORING_FEAT_NODROP 0x00000002
227#define IORING_FEAT_SUBMIT_STABLE 0x00000004
169 228
170inline_size 229inline_size
171int 230int
172evsys_io_uring_setup (unsigned entries, struct io_uring_params *params) 231evsys_io_uring_setup (unsigned entries, struct io_uring_params *params)
173{ 232{
… …
179evsys_io_uring_enter (int fd, unsigned to_submit, unsigned min_complete, unsigned flags, const sigset_t *sig, size_t sigsz) 238evsys_io_uring_enter (int fd, unsigned to_submit, unsigned min_complete, unsigned flags, const sigset_t *sig, size_t sigsz)
180{ 239{
181 return ev_syscall6 (SYS_io_uring_enter, fd, to_submit, min_complete, flags, sig, sigsz); 240 return ev_syscall6 (SYS_io_uring_enter, fd, to_submit, min_complete, flags, sig, sigsz);
182} 241}
183 242
243inline_size
244int
245evsys_io_uring_register (unsigned int fd, unsigned int opcode, void *arg, unsigned int nr_args)
246{
247 return ev_syscall4 (SYS_io_uring_register, fd, opcode, arg, nr_args);
248}
249
184/*****************************************************************************/ 250/*****************************************************************************/
185/* actual backed implementation */ 251/* actual backend implementation */
186 252
187/* we hope that volatile will make the compiler access this variables only once */ 253/* we hope that volatile will make the compiler access this variables only once */
188#define EV_SQ_VAR(name) *(volatile unsigned *)((char *)iouring_sq_ring + iouring_sq_ ## name)
189#define EV_CQ_VAR(name) *(volatile unsigned *)((char *)iouring_cq_ring + iouring_cq_ ## name) 254#define EV_SQ_VAR(name) *(volatile unsigned *)((char *)iouring_ring + iouring_sq_ ## name)
255#define EV_CQ_VAR(name) *(volatile unsigned *)((char *)iouring_ring + iouring_cq_ ## name)
190 256
191/* the index array */ 257/* the index array */
192#define EV_SQ_ARRAY ((unsigned *)((char *)iouring_sq_ring + iouring_sq_array)) 258#define EV_SQ_ARRAY ((unsigned *)((char *)iouring_ring + iouring_sq_array))
193 259
194/* the submit/completion queue entries */ 260/* the submit/completion queue entries */
195#define EV_SQES ((struct io_uring_sqe *) iouring_sqes) 261#define EV_SQES ((struct io_uring_sqe *) iouring_sqes)
196#define EV_CQES ((struct io_uring_cqe *)((char *)iouring_cq_ring + iouring_cq_cqes)) 262#define EV_CQES ((struct io_uring_cqe *)((char *)iouring_ring + iouring_cq_cqes))
263
264inline_speed
265int
266iouring_enter (EV_P_ ev_tstamp timeout)
267{
268 int res;
269
270 EV_RELEASE_CB;
271
272 res = evsys_io_uring_enter (iouring_fd, iouring_to_submit, 1,
273 timeout > EV_TS_CONST (0.) ? IORING_ENTER_GETEVENTS : 0, 0, 0);
274
275 assert (("libev: io_uring_enter did not consume all sqes", (res < 0 || res == iouring_to_submit)));
276
277 iouring_to_submit = 0;
278
279 EV_ACQUIRE_CB;
280
281 return res;
282}
283
284/* TODO: can we move things around so we don't need this forward-reference? */
285static void
286iouring_poll (EV_P_ ev_tstamp timeout);
197 287
198static 288static
199struct io_uring_sqe * 289struct io_uring_sqe *
200iouring_sqe_get (EV_P) 290iouring_sqe_get (EV_P)
201{ 291{
292 unsigned tail;
293
294 for (;;)
295 {
202 unsigned tail = EV_SQ_VAR (tail); 296 tail = EV_SQ_VAR (tail);
203 297
204 if (tail + 1 - EV_SQ_VAR (head) > EV_SQ_VAR (ring_entries)) 298 if (ecb_expect_true (tail + 1 - EV_SQ_VAR (head) <= EV_SQ_VAR (ring_entries)))
299 break; /* whats the problem, we have free sqes */
300
301 /* queue full, need to flush and possibly handle some events */
302
303#if EV_FEATURE_CODE
304 /* first we ask the kernel nicely, most often this frees up some sqes */
305 int res = iouring_enter (EV_A_ EV_TS_CONST (0.));
306
307 ECB_MEMORY_FENCE_ACQUIRE; /* better safe than sorry */
308
309 if (res >= 0)
310 continue; /* yes, it worked, try again */
311#endif
312
313 /* some problem, possibly EBUSY - do the full poll and let it handle any issues */
314
315 iouring_poll (EV_A_ EV_TS_CONST (0.));
316 /* iouring_poll should have done ECB_MEMORY_FENCE_ACQUIRE for us */
205 { 317 }
206 /* queue full, flush */
207 evsys_io_uring_enter (iouring_fd, iouring_to_submit, 0, 0, 0, 0);
208 iouring_to_submit = 0;
209 }
210 318
211 assert (("libev: io_uring queue full after flush", tail + 1 - EV_SQ_VAR (head) <= EV_SQ_VAR (ring_entries))); 319 /*assert (("libev: io_uring queue full after flush", tail + 1 - EV_SQ_VAR (head) <= EV_SQ_VAR (ring_entries)));*/
212 320
213 return EV_SQES + (tail & EV_SQ_VAR (ring_mask)); 321 return EV_SQES + (tail & EV_SQ_VAR (ring_mask));
214} 322}
215 323
216inline_size 324inline_size
217struct io_uring_sqe * 325struct io_uring_sqe *
218iouring_sqe_submit (EV_P_ struct io_uring_sqe *sqe) 326iouring_sqe_submit (EV_P_ struct io_uring_sqe *sqe)
219{ 327{
220 unsigned idx = sqe - EV_SQES; 328 unsigned idx = sqe - EV_SQES;
329
330 printf ("submit idx %d, op %d, fd %d, us5r %p, poll %d\n", idx, sqe->opcode, sqe->fd, sqe->user_data, sqe->poll_events);
221 331
222 EV_SQ_ARRAY [idx] = idx; 332 EV_SQ_ARRAY [idx] = idx;
223 ECB_MEMORY_FENCE_RELEASE; 333 ECB_MEMORY_FENCE_RELEASE;
224 ++EV_SQ_VAR (tail); 334 ++EV_SQ_VAR (tail);
225 /*ECB_MEMORY_FENCE_RELEASE; /* for the time being we assume this is not needed */ 335 /*ECB_MEMORY_FENCE_RELEASE; /* for the time being we assume this is not needed */
… …
236iouring_tfd_cb (EV_P_ struct ev_io *w, int revents) 346iouring_tfd_cb (EV_P_ struct ev_io *w, int revents)
237{ 347{
238 iouring_tfd_to = EV_TSTAMP_HUGE; 348 iouring_tfd_to = EV_TSTAMP_HUGE;
239} 349}
240 350
241static void
242iouring_epoll_cb (EV_P_ struct ev_io *w, int revents)
243{
244 epoll_poll (EV_A_ 0);
245}
246
247/* called for full and partial cleanup */ 351/* called for full and partial cleanup */
248ecb_cold 352ecb_cold
249static int 353static int
250iouring_internal_destroy (EV_P) 354iouring_internal_destroy (EV_P)
251{ 355{
252 close (iouring_tfd); 356 close (iouring_tfd);
253 close (iouring_fd); 357 close (iouring_fd);
254 358
255 if (iouring_sq_ring != MAP_FAILED) munmap (iouring_sq_ring, iouring_sq_ring_size); 359 if (iouring_ring != MAP_FAILED) munmap (iouring_ring, iouring_ring_size);
256 if (iouring_cq_ring != MAP_FAILED) munmap (iouring_cq_ring, iouring_cq_ring_size);
257 if (iouring_sqes != MAP_FAILED) munmap (iouring_sqes , iouring_sqes_size ); 360 if (iouring_sqes != MAP_FAILED) munmap (iouring_sqes, iouring_sqes_size);
258 361
259 if (ev_is_active (&iouring_epoll_w)) ev_ref (EV_A); ev_io_stop (EV_A_ &iouring_epoll_w); 362 if (ev_is_active (&iouring_tfd_w))
260 if (ev_is_active (&iouring_tfd_w )) ev_ref (EV_A); ev_io_stop (EV_A_ &iouring_tfd_w ); 363 {
364 ev_ref (EV_A);
365 ev_io_stop (EV_A_ &iouring_tfd_w);
366 }
261} 367}
262 368
263ecb_cold 369ecb_cold
264static int 370static int
265iouring_internal_init (EV_P) 371iouring_internal_init (EV_P)
266{ 372{
267 struct io_uring_params params = { 0 }; 373 struct io_uring_params params = { 0 };
374 uint32_t sq_size, cq_size;
375
376 params.flags = IORING_SETUP_CLAMP;
268 377
269 iouring_to_submit = 0; 378 iouring_to_submit = 0;
270 379
271 iouring_tfd = -1; 380 iouring_tfd = -1;
272 iouring_sq_ring = MAP_FAILED; 381 iouring_ring = MAP_FAILED;
273 iouring_cq_ring = MAP_FAILED;
274 iouring_sqes = MAP_FAILED; 382 iouring_sqes = MAP_FAILED;
275 383
276 for (;;) 384 if (!have_monotonic) /* cannot really happen, but what if11 */
277 { 385 return -1;
386
278 iouring_fd = evsys_io_uring_setup (iouring_entries, &params); 387 iouring_fd = evsys_io_uring_setup (iouring_entries, &params);
279 388
280 if (iouring_fd >= 0) 389 if (iouring_fd < 0)
281 break; /* yippie */
282
283 if (errno != EINVAL)
284 return -1; /* we failed */
285
286 /* EINVAL: lots of possible reasons, but maybe
287 * it is because we hit the unqueryable hardcoded size limit
288 */
289
290 /* we hit the limit already, give up */
291 if (iouring_max_entries)
292 return -1; 390 return -1;
293 391
294 /* first time we hit EINVAL? assume we hit the limit, so go back and retry */ 392 if ((~params.features) & (IORING_FEAT_NODROP | IORING_FEAT_SINGLE_MMAP | IORING_FEAT_SUBMIT_STABLE))
295 iouring_entries >>= 1; 393 return -1; /* we require the above features */
296 iouring_max_entries = iouring_entries;
297 }
298 394
395 /* TODO: remember somehow whether our queue size has been clamped */
396
299 iouring_sq_ring_size = params.sq_off.array + params.sq_entries * sizeof (unsigned); 397 sq_size = params.sq_off.array + params.sq_entries * sizeof (unsigned);
300 iouring_cq_ring_size = params.cq_off.cqes + params.cq_entries * sizeof (struct io_uring_cqe); 398 cq_size = params.cq_off.cqes + params.cq_entries * sizeof (struct io_uring_cqe);
399
400 iouring_ring_size = sq_size > cq_size ? sq_size : cq_size;
301 iouring_sqes_size = params.sq_entries * sizeof (struct io_uring_sqe); 401 iouring_sqes_size = params.sq_entries * sizeof (struct io_uring_sqe);
302 402
303 iouring_sq_ring = mmap (0, iouring_sq_ring_size, PROT_READ | PROT_WRITE, 403 iouring_ring = mmap (0, iouring_ring_size, PROT_READ | PROT_WRITE,
304 MAP_SHARED | MAP_POPULATE, iouring_fd, IORING_OFF_SQ_RING); 404 MAP_SHARED | MAP_POPULATE, iouring_fd, IORING_OFF_SQ_RING);
305 iouring_cq_ring = mmap (0, iouring_cq_ring_size, PROT_READ | PROT_WRITE,
306 MAP_SHARED | MAP_POPULATE, iouring_fd, IORING_OFF_CQ_RING);
307 iouring_sqes = mmap (0, iouring_sqes_size, PROT_READ | PROT_WRITE, 405 iouring_sqes = mmap (0, iouring_sqes_size, PROT_READ | PROT_WRITE,
308 MAP_SHARED | MAP_POPULATE, iouring_fd, IORING_OFF_SQES); 406 MAP_SHARED | MAP_POPULATE, iouring_fd, IORING_OFF_SQES);
309 407
310 if (iouring_sq_ring == MAP_FAILED || iouring_cq_ring == MAP_FAILED || iouring_sqes == MAP_FAILED) 408 if (iouring_ring == MAP_FAILED || iouring_sqes == MAP_FAILED)
311 return -1; 409 return -1;
312 410
313 iouring_sq_head = params.sq_off.head; 411 iouring_sq_head = params.sq_off.head;
314 iouring_sq_tail = params.sq_off.tail; 412 iouring_sq_tail = params.sq_off.tail;
315 iouring_sq_ring_mask = params.sq_off.ring_mask; 413 iouring_sq_ring_mask = params.sq_off.ring_mask;
… …
323 iouring_cq_ring_mask = params.cq_off.ring_mask; 421 iouring_cq_ring_mask = params.cq_off.ring_mask;
324 iouring_cq_ring_entries = params.cq_off.ring_entries; 422 iouring_cq_ring_entries = params.cq_off.ring_entries;
325 iouring_cq_overflow = params.cq_off.overflow; 423 iouring_cq_overflow = params.cq_off.overflow;
326 iouring_cq_cqes = params.cq_off.cqes; 424 iouring_cq_cqes = params.cq_off.cqes;
327 425
426 iouring_tfd_to = EV_TSTAMP_HUGE;
427
328 iouring_tfd = timerfd_create (CLOCK_MONOTONIC, TFD_CLOEXEC); 428 iouring_tfd = timerfd_create (CLOCK_MONOTONIC, TFD_CLOEXEC);
329 429
330 if (iouring_tfd < 0) 430 if (iouring_tfd < 0)
331 return iouring_tfd; 431 return -1;
332
333 iouring_tfd_to = EV_TSTAMP_HUGE;
334 432
335 return 0; 433 return 0;
336} 434}
337 435
338ecb_cold 436ecb_cold
… …
342 iouring_internal_destroy (EV_A); 440 iouring_internal_destroy (EV_A);
343 441
344 while (iouring_internal_init (EV_A) < 0) 442 while (iouring_internal_init (EV_A) < 0)
345 ev_syserr ("(libev) io_uring_setup"); 443 ev_syserr ("(libev) io_uring_setup");
346 444
347 /* forking epoll should also effectively unregister all fds from the backend */
348 epoll_fork (EV_A);
349 /* epoll_fork already did this. hopefully */
350 /*fd_rearm_all (EV_A);*/ 445 fd_rearm_all (EV_A);
351
352 ev_io_stop (EV_A_ &iouring_epoll_w);
353 ev_io_set (EV_A_ &iouring_epoll_w, backend_fd, EV_READ);
354 ev_io_start (EV_A_ &iouring_epoll_w);
355 446
356 ev_io_stop (EV_A_ &iouring_tfd_w); 447 ev_io_stop (EV_A_ &iouring_tfd_w);
357 ev_io_set (EV_A_ &iouring_tfd_w, iouring_tfd, EV_READ); 448 ev_io_set (EV_A_ &iouring_tfd_w, iouring_tfd, EV_READ);
358 ev_io_start (EV_A_ &iouring_tfd_w); 449 ev_io_start (EV_A_ &iouring_tfd_w);
359} 450}
… …
361/*****************************************************************************/ 452/*****************************************************************************/
362 453
363static void 454static void
364iouring_modify (EV_P_ int fd, int oev, int nev) 455iouring_modify (EV_P_ int fd, int oev, int nev)
365{ 456{
366 fprintf (stderr,"modify %d (%d, %d) %d\n", fd, oev,nev, anfds[fd].eflags);//D
367 if (ecb_expect_false (anfds [fd].eflags))
368 {
369 /* we handed this fd over to epoll, so undo this first */
370 /* we do it manually because the optimisations on epoll_modify won't do us any good */
371 epoll_ctl (iouring_fd, EPOLL_CTL_DEL, fd, 0);
372 anfds [fd].eflags = 0;
373 oev = 0;
374 }
375
376 if (oev) 457 if (oev)
377 { 458 {
378 /* we assume the sqe's are all "properly" initialised */ 459 /* we assume the sqe's are all "properly" initialised */
379 struct io_uring_sqe *sqe = iouring_sqe_get (EV_A); 460 struct io_uring_sqe *sqe = iouring_sqe_get (EV_A);
380 sqe->opcode = IORING_OP_POLL_REMOVE; 461 sqe->opcode = IORING_OP_POLL_REMOVE;
381 sqe->fd = fd; 462 sqe->fd = fd;
463 /* Jens Axboe notified me that user_data is not what is documented, but is
464 * some kind of unique ID that has to match, otherwise the request cannot
465 * be removed. Since we don't *really* have that, we pass in the old
466 * generation counter - if that fails, too bad, it will hopefully be removed
467 * at close time and then be ignored. */
468 sqe->addr = (uint32_t)fd | ((__u64)(uint32_t)anfds [fd].egen << 32);
382 sqe->user_data = -1; 469 sqe->user_data = (uint64_t)-1;
383 iouring_sqe_submit (EV_A_ sqe); 470 iouring_sqe_submit (EV_A_ sqe);
384 }
385 471
386 /* increment generation counter to avoid handling old events */ 472 /* increment generation counter to avoid handling old events */
387 ++anfds [fd].egen; 473 ++anfds [fd].egen;
474 }
388 475
389 if (nev) 476 if (nev)
390 { 477 {
391 struct io_uring_sqe *sqe = iouring_sqe_get (EV_A); 478 struct io_uring_sqe *sqe = iouring_sqe_get (EV_A);
392 sqe->opcode = IORING_OP_POLL_ADD; 479 sqe->opcode = IORING_OP_POLL_ADD;
393 sqe->fd = fd; 480 sqe->fd = fd;
481 sqe->addr = 0;
394 sqe->user_data = (uint32_t)fd | ((__u64)anfds [fd].egen << 32); 482 sqe->user_data = (uint32_t)fd | ((__u64)(uint32_t)anfds [fd].egen << 32);
395 sqe->poll_events = 483 sqe->poll_events =
396 (nev & EV_READ ? POLLIN : 0) 484 (nev & EV_READ ? POLLIN : 0)
397 | (nev & EV_WRITE ? POLLOUT : 0); 485 | (nev & EV_WRITE ? POLLOUT : 0);
398 iouring_sqe_submit (EV_A_ sqe); 486 iouring_sqe_submit (EV_A_ sqe);
399 } 487 }
… …
428{ 516{
429 int fd = cqe->user_data & 0xffffffffU; 517 int fd = cqe->user_data & 0xffffffffU;
430 uint32_t gen = cqe->user_data >> 32; 518 uint32_t gen = cqe->user_data >> 32;
431 int res = cqe->res; 519 int res = cqe->res;
432 520
433 /* ignore fd removal events, if there are any. TODO: verify */ 521 /* user_data -1 is a remove that we are not atm. interested in */
434 if (cqe->user_data == (__u64)-1) 522 if (cqe->user_data == (uint64_t)-1)
435 abort ();//D 523 return;
436 524
437 assert (("libev: io_uring fd must be in-bounds", fd >= 0 && fd < anfdmax)); 525 assert (("libev: io_uring fd must be in-bounds", fd >= 0 && fd < anfdmax));
438 526
439 /* documentation lies, of course. the result value is NOT like 527 /* documentation lies, of course. the result value is NOT like
440 * normal syscalls, but like linux raw syscalls, i.e. negative 528 * normal syscalls, but like linux raw syscalls, i.e. negative
441 * error numbers. fortunate, as otherwise there would be no way 529 * error numbers. fortunate, as otherwise there would be no way
442 * to get error codes at all. still, why not document this? 530 * to get error codes at all. still, why not document this?
443 */ 531 */
444 532
445 /* ignore event if generation doesn't match */ 533 /* ignore event if generation doesn't match */
534 /* other than skipping removal events, */
446 /* this should actually be very rare */ 535 /* this should actually be very rare */
447 if (ecb_expect_false ((uint32_t)anfds [fd].egen != gen)) 536 if (ecb_expect_false (gen != (uint32_t)anfds [fd].egen))
448 return; 537 return;
449 538
450 if (ecb_expect_false (res < 0)) 539 if (ecb_expect_false (res < 0))
451 { 540 {
452 if (res == -EINVAL) 541 /*TODO: EINVAL handling (was something failed with this fd)*/
453 {
454 /* we assume this error code means the fd/poll combination is buggy
455 * and fall back to epoll.
456 * this error code might also indicate a bug, but the kernel doesn't
457 * distinguish between those two conditions, so... sigh...
458 */
459 542
460 epoll_modify (EV_A_ fd, 0, anfds [fd].events);
461 }
462 else if (res == -EBADF) 543 if (res == -EBADF)
463 { 544 {
464 assert (("libev: event loop rejected bad fd", res != -EBADF)); 545 assert (("libev: event loop rejected bad fd", res != -EBADF));
465 fd_kill (EV_A_ fd); 546 fd_kill (EV_A_ fd);
466 } 547 }
467 else 548 else
… …
471 } 552 }
472 553
473 return; 554 return;
474 } 555 }
475 556
476 fprintf (stderr, "fd %d event, rearm\n", fd);//D
477
478 /* feed events, we do not expect or handle POLLNVAL */ 557 /* feed events, we do not expect or handle POLLNVAL */
479 fd_event ( 558 fd_event (
480 EV_A_ 559 EV_A_
481 fd, 560 fd,
482 (res & (POLLOUT | POLLERR | POLLHUP) ? EV_WRITE : 0) 561 (res & (POLLOUT | POLLERR | POLLHUP) ? EV_WRITE : 0)
… …
495iouring_overflow (EV_P) 574iouring_overflow (EV_P)
496{ 575{
497 /* we have two options, resize the queue (by tearing down 576 /* we have two options, resize the queue (by tearing down
498 * everything and recreating it, or living with it 577 * everything and recreating it, or living with it
499 * and polling. 578 * and polling.
500 * we implement this by resizing tghe queue, and, if that fails, 579 * we implement this by resizing the queue, and, if that fails,
501 * we just recreate the state on every failure, which 580 * we just recreate the state on every failure, which
502 * kind of is a very inefficient poll. 581 * kind of is a very inefficient poll.
503 * one danger is, due to the bios toward lower fds, 582 * one danger is, due to the bios toward lower fds,
504 * we will only really get events for those, so 583 * we will only really get events for those, so
505 * maybe we need a poll() fallback, after all. 584 * maybe we need a poll() fallback, after all.
… …
517 else 596 else
518 { 597 {
519 /* we hit the kernel limit, we should fall back to something else. 598 /* we hit the kernel limit, we should fall back to something else.
520 * we can either poll() a few times and hope for the best, 599 * we can either poll() a few times and hope for the best,
521 * poll always, or switch to epoll. 600 * poll always, or switch to epoll.
522 * since we use epoll anyways, go epoll. 601 * TODO: is this necessary with newer kernels?
523 */ 602 */
524 603
525 iouring_internal_destroy (EV_A); 604 iouring_internal_destroy (EV_A);
526 605
527 /* this should make it so that on return, we don'T call any uring functions */ 606 /* this should make it so that on return, we don't call any uring functions */
528 iouring_to_submit = 0; 607 iouring_to_submit = 0;
529 608
530 for (;;) 609 for (;;)
531 { 610 {
532 backend = epoll_init (EV_A_ 0); 611 backend = epoll_init (EV_A_ 0);
… …
573 652
574static void 653static void
575iouring_poll (EV_P_ ev_tstamp timeout) 654iouring_poll (EV_P_ ev_tstamp timeout)
576{ 655{
577 /* if we have events, no need for extra syscalls, but we might have to queue events */ 656 /* if we have events, no need for extra syscalls, but we might have to queue events */
657 /* we also clar the timeout if there are outstanding fdchanges */
658 /* the latter should only happen if both the sq and cq are full, most likely */
659 /* because we have a lot of event sources that immediately complete */
660 /* TODO: fdchacngecnt is always 0 because fd_reify does not have two buffers yet */
578 if (iouring_handle_cq (EV_A)) 661 if (iouring_handle_cq (EV_A) || fdchangecnt)
579 timeout = 0.; 662 timeout = EV_TS_CONST (0.);
580 else 663 else
581 /* no events, so maybe wait for some */ 664 /* no events, so maybe wait for some */
582 iouring_tfd_update (EV_A_ timeout); 665 iouring_tfd_update (EV_A_ timeout);
583 666
584 /* only enter the kernel if we have somethign to submit, or we need to wait */ 667 /* only enter the kernel if we have something to submit, or we need to wait */
585 if (timeout || iouring_to_submit) 668 if (timeout || iouring_to_submit)
586 { 669 {
587 int res; 670 int res = iouring_enter (EV_A_ timeout);
588
589 EV_RELEASE_CB;
590
591 res = evsys_io_uring_enter (iouring_fd, iouring_to_submit, 1,
592 timeout ? IORING_ENTER_GETEVENTS : 0, 0, 0);
593 iouring_to_submit = 0;
594
595 EV_ACQUIRE_CB;
596 671
597 if (ecb_expect_false (res < 0)) 672 if (ecb_expect_false (res < 0))
598 if (errno == EINTR) 673 if (errno == EINTR)
599 /* ignore */; 674 /* ignore */;
675 else if (errno == EBUSY)
676 /* cq full, cannot submit - should be rare because we flush the cq first, so simply ignore */;
600 else 677 else
601 ev_syserr ("(libev) iouring setup"); 678 ev_syserr ("(libev) iouring setup");
602 else 679 else
603 iouring_handle_cq (EV_A); 680 iouring_handle_cq (EV_A);
604 } 681 }
… …
606 683
607inline_size 684inline_size
608int 685int
609iouring_init (EV_P_ int flags) 686iouring_init (EV_P_ int flags)
610{ 687{
611 if (!epoll_init (EV_A_ 0))
612 return 0;
613
614 ev_io_init (EV_A_ &iouring_epoll_w, iouring_epoll_cb, backend_fd, EV_READ);
615 ev_set_priority (&iouring_epoll_w, EV_MAXPRI);
616
617 ev_io_init (&iouring_tfd_w, iouring_tfd_cb, iouring_tfd, EV_READ);
618 ev_set_priority (&iouring_tfd_w, EV_MAXPRI);
619
620 iouring_entries = IOURING_INIT_ENTRIES; 688 iouring_entries = IOURING_INIT_ENTRIES;
621 iouring_max_entries = 0; 689 iouring_max_entries = 0;
622 690
623 if (iouring_internal_init (EV_A) < 0) 691 if (iouring_internal_init (EV_A) < 0)
624 { 692 {
625 iouring_internal_destroy (EV_A); 693 iouring_internal_destroy (EV_A);
626 return 0; 694 return 0;
627 } 695 }
628 696
629 ev_io_start (EV_A_ &iouring_epoll_w); 697 ev_io_init (&iouring_tfd_w, iouring_tfd_cb, iouring_tfd, EV_READ);
630 ev_unref (EV_A); /* watcher should not keep loop alive */ 698 ev_set_priority (&iouring_tfd_w, EV_MINPRI);
631
632 ev_io_start (EV_A_ &iouring_tfd_w); 699 ev_io_start (EV_A_ &iouring_tfd_w);
633 ev_unref (EV_A); /* watcher should not keep loop alive */ 700 ev_unref (EV_A); /* watcher should not keep loop alive */
634 701
635 backend_modify = iouring_modify; 702 backend_modify = iouring_modify;
636 backend_poll = iouring_poll; 703 backend_poll = iouring_poll;
… …
641inline_size 708inline_size
642void 709void
643iouring_destroy (EV_P) 710iouring_destroy (EV_P)
644{ 711{
645 iouring_internal_destroy (EV_A); 712 iouring_internal_destroy (EV_A);
646 epoll_destroy (EV_A);
647} 713}
648 714

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