libev/ev_linuxaio.c

/*
 * libev linux aio fd activity backend
 *
 * Copyright (c) 2019 Marc Alexander Lehmann <libev@schmorp.de>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modifica-
 * tion, are permitted provided that the following conditions are met:
 *
 *   1.  Redistributions of source code must retain the above copyright notice,
 *       this list of conditions and the following disclaimer.
 *
 *   2.  Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MER-
 * CHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO
 * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPE-
 * CIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTH-
 * ERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * Alternatively, the contents of this file may be used under the terms of
 * the GNU General Public License ("GPL") version 2 or any later version,
 * in which case the provisions of the GPL are applicable instead of
 * the above. If you wish to allow the use of your version of this file
 * only under the terms of the GPL and not to allow others to use your
 * version of this file under the BSD license, indicate your decision
 * by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL. If you do not delete the
 * provisions above, a recipient may use your version of this file under
 * either the BSD or the GPL.
 */

#include <sys/time.h> /* actually linux/time.h, but we must assume they are compatible */
#include <linux/aio_abi.h>

/* we try to fill 4kn pages exactly.
 * the ring buffer header is 32 bytes, every io event is 32 bytes.
 * the kernel takes the io event number, doubles it, adds 2, adds the ring buffer
 * so the calculation below will use "exactly" 8kB for the ring buffer
 */
#define EV_LINUXAIO_DEPTH (256 / 2 - 2 - 1) /* max. number of io events per batch */

/*****************************************************************************/
/* syscall wrapdadoop */

#include <sys/syscall.h> /* no glibc wrappers */

/* aio_abi.h is not verioned in any way, so we cannot test for its existance */
#define IOCB_CMD_POLL 5

/* taken from linux/fs/aio.c */
#define AIO_RING_MAGIC                  0xa10a10a1
#define AIO_RING_INCOMPAT_FEATURES      0
struct aio_ring
{
  unsigned id;    /* kernel internal index number */
  unsigned nr;    /* number of io_events */
  unsigned head;  /* Written to by userland or by kernel. */
  unsigned tail;

  unsigned magic;
  unsigned compat_features;
  unsigned incompat_features;
  unsigned header_length;  /* size of aio_ring */

  struct io_event io_events[0];
};

static int
ev_io_setup (unsigned nr_events, aio_context_t *ctx_idp)
{
  return syscall (SYS_io_setup, nr_events, ctx_idp);
}

static int
ev_io_destroy (aio_context_t ctx_id)
{
  return syscall (SYS_io_destroy, ctx_id);
}

static int
ev_io_submit (aio_context_t ctx_id, long nr, struct iocb *cbp[])
{
  return syscall (SYS_io_submit, ctx_id, nr, cbp);
}

static int
ev_io_cancel (aio_context_t ctx_id, struct iocb *cbp, struct io_event *result)
{
  return syscall (SYS_io_cancel, ctx_id, cbp, result);
}

static int
ev_io_getevents (aio_context_t ctx_id, long min_nr, long nr, struct io_event *events, struct timespec *timeout)
{
  return syscall (SYS_io_getevents, ctx_id, min_nr, nr, events, timeout);
}

typedef void (*ev_io_cb) (long nr, struct io_event *events);

/*****************************************************************************/
/* actual backed implementation */

/* two iocbs for every fd, one for read, one for write */
typedef struct aniocb
{
  struct iocb io;
  /*int inuse;*/
} *ANIOCBP;

inline_size
void
linuxaio_array_needsize_iocbp (ANIOCBP *base, int count)
{
  /* TODO: quite the overhead to allocate every iocb separately */
  while (count--)
    {
      *base = (ANIOCBP)ev_malloc (sizeof (**base));
      memset (*base, 0, sizeof (**base));
      /* would be nice to initialize fd/data as well */
      (*base)->io.aio_lio_opcode = IOCB_CMD_POLL;
      ++base;
    }
}

static void
linuxaio_free_iocbp (EV_P)
{
  while (linuxaio_iocbpmax--)
    ev_free (linuxaio_iocbps [linuxaio_iocbpmax]);

  linuxaio_iocbpmax = 0;
}

static void
linuxaio_modify (EV_P_ int fd, int oev, int nev)
{
  /* TODO: full zero initialize required? */
  array_needsize (ANIOCBP, linuxaio_iocbps, linuxaio_iocbpmax, fd + 1, linuxaio_array_needsize_iocbp);
  struct aniocb *iocb = linuxaio_iocbps [fd];

  if (iocb->io.aio_buf)
    ev_io_cancel (linuxaio_ctx, &iocb->io, (void *)0);

  if (nev)
    {
      iocb->io.aio_data       = fd;
      iocb->io.aio_fildes     = fd;
      iocb->io.aio_buf        =
          (nev & EV_READ ? POLLIN : 0)
          | (nev & EV_WRITE ? POLLOUT : 0);

      /* queue iocb up for io_submit */
      /* this assumes we only ever get one call per fd per loop iteration */
      ++linuxaio_submitcnt;
      array_needsize (struct iocb *, linuxaio_submits, linuxaio_submitmax, linuxaio_submitcnt, array_needsize_noinit);
      linuxaio_submits [linuxaio_submitcnt - 1] = &iocb->io;
    }
}

static void
linuxaio_parse_events (EV_P_ struct io_event *ev, int nr)
{
  while (nr)
    {
      int fd  = ev->data;
      int res = ev->res;

      assert (("libev: iocb fd must be in-bounds", fd >= 0 && fd < anfdxmax));

      /* linux aio is oneshot: rearm fd */
      linuxaio_iocbps [fd]->io.aio_buf = 0;
      anfds [fd].events = 0;
      fd_change (EV_A_ fd, 0);

      /* feed events, we do not expect or handle POLLNVAL */
      if (ecb_expect_false (res & POLLNVAL))
        fd_kill (EV_A_ fd);
      else
        fd_event (
          EV_A_
          fd,
          (res & (POLLOUT | POLLERR | POLLHUP) ? EV_WRITE : 0)
          | (res & (POLLIN | POLLERR | POLLHUP) ? EV_READ : 0)
        );

      --nr;
      ++ev;
    }
}

/* get any events from ringbuffer, return true if any were handled */
static int
linuxaio_get_events_from_ring (EV_P)
{
  struct aio_ring *ring = (struct aio_ring *)linuxaio_ctx;

  ECB_MEMORY_FENCE_ACQUIRE;

  unsigned head = ring->head;
  unsigned tail = *(volatile unsigned *)&ring->tail;

  if (ring->magic != AIO_RING_MAGIC
      || ring->incompat_features != AIO_RING_INCOMPAT_FEATURES
      || ring->header_length != sizeof (struct aio_ring) /* TODO: or use it to find io_event[0]? */
      || head == tail)
    return 0;

  /* parse all available events, but only once, to avoid starvation */
  if (tail > head) /* normal case around */
    linuxaio_parse_events (EV_A_ ring->io_events + head, tail - head);
  else
    {
      /* wrapped around */
      linuxaio_parse_events (EV_A_ ring->io_events + head, ring->nr - head);
      linuxaio_parse_events (EV_A_ ring->io_events, tail);
    }

  ring->head = tail;

  return 1;
}

/* read at least one event from kernel, or timeout */
inline_size
void
linuxaio_get_events (EV_P_ ev_tstamp timeout)
{
  struct timespec ts;
  struct io_event ioev;
  int res;

  if (linuxaio_get_events_from_ring (EV_A))
    return;

  /* no events, so wait for at least one, then poll ring buffer again */
  /* this degraded to one event per loop iteration */
  /* if the ring buffer changes layout, but so be it */

  ts.tv_sec  = (long)timeout;
  ts.tv_nsec = (long)((timeout - ts.tv_sec) * 1e9);

  res = ev_io_getevents (linuxaio_ctx, 1, 1, &ioev, &ts);

  if (res < 0)
    ev_syserr ("(libev) io_getevents");
  else if (res)
    {
      /* at least one event received, handle it and any remaining ones in the ring buffer */
      linuxaio_parse_events (EV_A_ &ioev, 1);
      linuxaio_get_events_from_ring (EV_A);
    }
}

static void
linuxaio_poll (EV_P_ ev_tstamp timeout)
{
  int submitted;

  /* first phase: submit new iocbs */

  /* io_submit might return less than the requested number of iocbs */
  /* this is, afaics, only because of errors, but we go by the book and use a loop, */
  /* which allows us to pinpoint the errornous iocb */
  for (submitted = 0; submitted < linuxaio_submitcnt; )
    {
      int res = ev_io_submit (linuxaio_ctx, linuxaio_submitcnt - submitted, linuxaio_submits + submitted);

      if (res < 0)
        if (errno == EAGAIN)
          {
            /* This happens when the ring buffer is full, at least. I assume this means
             * that the event was queued synchronously during io_submit, and thus
             * the buffer overflowd.
             * In this case, we just try next loop iteration.
             */
            memcpy (linuxaio_submits, linuxaio_submits + submitted, (linuxaio_submitcnt - submitted) * sizeof (*linuxaio_submits));
            linuxaio_submitcnt -= submitted;
            timeout = 0;
            break;
          }
        else
          /* TODO: we get EAGAIN when the ring buffer is full for some reason */
          /* TODO: should we always just try next time? */
          ev_syserr ("(libev) io_submit");

      submitted += res;
    }

  linuxaio_submitcnt = 0;

  /* second phase: fetch and parse events */

  linuxaio_get_events (EV_A_ timeout);
}

inline_size
int
linuxaio_init (EV_P_ int flags)
{
  /* would be great to have a nice test for IOCB_CMD_POLL instead */
  if (ev_linux_version () < 0x041200) /* 4.18 introduced IOCB_CMD_POLL */
    return 0;

  if (ev_io_setup (EV_LINUXAIO_DEPTH, &linuxaio_ctx) < 0)
    return 0;

  backend_modify  = linuxaio_modify;
  backend_poll    = linuxaio_poll;

  linuxaio_iocbpmax = 0;
  linuxaio_iocbps = 0;

  linuxaio_submits = 0;
  linuxaio_submitmax = 0;
  linuxaio_submitcnt = 0;

  return EVBACKEND_LINUXAIO;
}

inline_size
void
linuxaio_destroy (EV_P)
{
  linuxaio_free_iocbp (EV_A);
  ev_io_destroy (linuxaio_ctx);
}

inline_size
void
linuxaio_fork (EV_P)
{
  abort ();//D
}

Revision:	1.1
Committed:	Thu Jun 20 22:44:59 2019 UTC (4 years, 10 months ago) by root
Content type:	text/plain
Branch:	MAIN
Log Message:	* empty log message *
#	Content
1	/*
2	* libev linux aio fd activity backend
3	*
4	* Copyright (c) 2019 Marc Alexander Lehmann <libev@schmorp.de>
5	* All rights reserved.
6	*
7	* Redistribution and use in source and binary forms, with or without modifica-
8	* tion, are permitted provided that the following conditions are met:
9	*
10	* 1. Redistributions of source code must retain the above copyright notice,
11	* this list of conditions and the following disclaimer.
12	*
13	* 2. Redistributions in binary form must reproduce the above copyright
14	* notice, this list of conditions and the following disclaimer in the
15	* documentation and/or other materials provided with the distribution.
16	*
17	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
18	* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MER-
19	* CHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
20	* EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPE-
21	* CIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
22	* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
23	* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
24	* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTH-
25	* ERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
26	* OF THE POSSIBILITY OF SUCH DAMAGE.
27	*
28	* Alternatively, the contents of this file may be used under the terms of
29	* the GNU General Public License ("GPL") version 2 or any later version,
30	* in which case the provisions of the GPL are applicable instead of
31	* the above. If you wish to allow the use of your version of this file
32	* only under the terms of the GPL and not to allow others to use your
33	* version of this file under the BSD license, indicate your decision
34	* by deleting the provisions above and replace them with the notice
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
37	* either the BSD or the GPL.
38	*/
39
40	#include <sys/time.h> /* actually linux/time.h, but we must assume they are compatible */
41	#include <linux/aio_abi.h>
42
43	/* we try to fill 4kn pages exactly.
44	* the ring buffer header is 32 bytes, every io event is 32 bytes.
45	* the kernel takes the io event number, doubles it, adds 2, adds the ring buffer
46	* so the calculation below will use "exactly" 8kB for the ring buffer
47	*/
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
60	#define AIO_RING_INCOMPAT_FEATURES 0
61	struct aio_ring
62	{
63	unsigned id; /* kernel internal index number */
64	unsigned nr; /* number of io_events */
65	unsigned head; /* Written to by userland or by kernel. */
66	unsigned tail;
67
68	unsigned magic;
69	unsigned compat_features;
70	unsigned incompat_features;
71	unsigned header_length; /* size of aio_ring */
72
73	struct io_event io_events[0];
74	};
75
76	static int
77	ev_io_setup (unsigned nr_events, aio_context_t *ctx_idp)
78	{
79	return syscall (SYS_io_setup, nr_events, ctx_idp);
80	}
81
82	static int
83	ev_io_destroy (aio_context_t ctx_id)
84	{
85	return syscall (SYS_io_destroy, ctx_id);
86	}
87
88	static int
89	ev_io_submit (aio_context_t ctx_id, long nr, struct iocb *cbp[])
90	{
91	return syscall (SYS_io_submit, ctx_id, nr, cbp);
92	}
93
94	static int
95	ev_io_cancel (aio_context_t ctx_id, struct iocb cbp, struct io_event result)
96	{
97	return syscall (SYS_io_cancel, ctx_id, cbp, result);
98	}
99
100	static int
101	ev_io_getevents (aio_context_t ctx_id, long min_nr, long nr, struct io_event events, struct timespec timeout)
102	{
103	return syscall (SYS_io_getevents, ctx_id, min_nr, nr, events, timeout);
104	}
105
106	typedef void (ev_io_cb) (long nr, struct io_event events);
107
108	/*****************************************************************************/
109	/* actual backed implementation */
110
111	/* two iocbs for every fd, one for read, one for write */
112	typedef struct aniocb
113	{
114	struct iocb io;
115	/int inuse;/
116	} *ANIOCBP;
117
118	inline_size
119	void
120	linuxaio_array_needsize_iocbp (ANIOCBP *base, int count)
121	{
122	/* TODO: quite the overhead to allocate every iocb separately */
123	while (count--)
124	{
125	base = (ANIOCBP)ev_malloc (sizeof (*base));
126	memset (base, 0, sizeof (*base));
127	/* would be nice to initialize fd/data as well */
128	(*base)->io.aio_lio_opcode = IOCB_CMD_POLL;
129	++base;
130	}
131	}
132
133	static void
134	linuxaio_free_iocbp (EV_P)
135	{
136	while (linuxaio_iocbpmax--)
137	ev_free (linuxaio_iocbps [linuxaio_iocbpmax]);
138
139	linuxaio_iocbpmax = 0;
140	}
141
142	static void
143	linuxaio_modify (EV_P_ int fd, int oev, int nev)
144	{
145	/* TODO: full zero initialize required? */
146	array_needsize (ANIOCBP, linuxaio_iocbps, linuxaio_iocbpmax, fd + 1, linuxaio_array_needsize_iocbp);
147	struct aniocb *iocb = linuxaio_iocbps [fd];
148
149	if (iocb->io.aio_buf)
150	ev_io_cancel (linuxaio_ctx, &iocb->io, (void *)0);
151
152	if (nev)
153	{
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 */
161	/* this assumes we only ever get one call per fd per loop iteration */
162	++linuxaio_submitcnt;
163	array_needsize (struct iocb *, linuxaio_submits, linuxaio_submitmax, linuxaio_submitcnt, array_needsize_noinit);
164	linuxaio_submits [linuxaio_submitcnt - 1] = &iocb->io;
165	}
166	}
167
168	static void
169	linuxaio_parse_events (EV_P_ struct io_event *ev, int nr)
170	{
171	while (nr)
172	{
173	int fd = ev->data;
174	int res = ev->res;
175
176	assert (("libev: iocb fd must be in-bounds", fd >= 0 && fd < anfdxmax));
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
183	/* 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 (
188	EV_A_
189	fd,
190	(res & (POLLOUT \| POLLERR \| POLLHUP) ? EV_WRITE : 0)
191	\| (res & (POLLIN \| POLLERR \| POLLHUP) ? EV_READ : 0)
192	);
193
194	--nr;
195	++ev;
196	}
197	}
198
199	/* get any events from ringbuffer, return true if any were handled */
200	static int
201	linuxaio_get_events_from_ring (EV_P)
202	{
203	struct aio_ring ring = (struct aio_ring )linuxaio_ctx;
204
205	ECB_MEMORY_FENCE_ACQUIRE;
206
207	unsigned head = ring->head;
208	unsigned tail = (volatile unsigned )&ring->tail;
209
210	if (ring->magic != AIO_RING_MAGIC
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;
215
216	/* parse all available events, but only once, to avoid starvation */
217	if (tail > head) /* normal case around */
218	linuxaio_parse_events (EV_A_ ring->io_events + head, tail - head);
219	else
220	{
221	/* wrapped around */
222	linuxaio_parse_events (EV_A_ ring->io_events + head, ring->nr - head);
223	linuxaio_parse_events (EV_A_ ring->io_events, tail);
224	}
225
226	ring->head = tail;
227
228	return 1;
229	}
230
231	/* read at least one event from kernel, or timeout */
232	inline_size
233	void
234	linuxaio_get_events (EV_P_ ev_tstamp timeout)
235	{
236	struct timespec ts;
237	struct io_event ioev;
238	int res;
239
240	if (linuxaio_get_events_from_ring (EV_A))
241	return;
242
243	/* no events, so wait for at least one, then poll ring buffer again */
244	/* this degraded to one event per loop iteration */
245	/* if the ring buffer changes layout, but so be it */
246
247	ts.tv_sec = (long)timeout;
248	ts.tv_nsec = (long)((timeout - ts.tv_sec) * 1e9);
249
250	res = ev_io_getevents (linuxaio_ctx, 1, 1, &ioev, &ts);
251
252	if (res < 0)
253	ev_syserr ("(libev) io_getevents");
254	else if (res)
255	{
256	/* at least one event received, handle it and any remaining ones in the ring buffer */
257	linuxaio_parse_events (EV_A_ &ioev, 1);
258	linuxaio_get_events_from_ring (EV_A);
259	}
260	}
261
262	static void
263	linuxaio_poll (EV_P_ ev_tstamp timeout)
264	{
265	int submitted;
266
267	/* first phase: submit new iocbs */
268
269	/* 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, */
271	/* which allows us to pinpoint the errornous iocb */
272	for (submitted = 0; submitted < linuxaio_submitcnt; )
273	{
274	int res = ev_io_submit (linuxaio_ctx, linuxaio_submitcnt - submitted, linuxaio_submits + submitted);
275
276	if (res < 0)
277	if (errno == EAGAIN)
278	{
279	/* This happens when the ring buffer is full, at least. I assume this means
280	* that the event was queued synchronously during io_submit, and thus
281	* the buffer overflowd.
282	* In this case, we just try next loop iteration.
283	*/
284	memcpy (linuxaio_submits, linuxaio_submits + submitted, (linuxaio_submitcnt - submitted) * sizeof (*linuxaio_submits));
285	linuxaio_submitcnt -= submitted;
286	timeout = 0;
287	break;
288	}
289	else
290	/* TODO: we get EAGAIN when the ring buffer is full for some reason */
291	/* TODO: should we always just try next time? */
292	ev_syserr ("(libev) io_submit");
293
294	submitted += res;
295	}
296
297	linuxaio_submitcnt = 0;
298
299	/* second phase: fetch and parse events */
300
301	linuxaio_get_events (EV_A_ timeout);
302	}
303
304	inline_size
305	int
306	linuxaio_init (EV_P_ int flags)
307	{
308	/* 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 */
310	return 0;
311
312	if (ev_io_setup (EV_LINUXAIO_DEPTH, &linuxaio_ctx) < 0)
313	return 0;
314
315	backend_modify = linuxaio_modify;
316	backend_poll = linuxaio_poll;
317
318	linuxaio_iocbpmax = 0;
319	linuxaio_iocbps = 0;
320
321	linuxaio_submits = 0;
322	linuxaio_submitmax = 0;
323	linuxaio_submitcnt = 0;
324
325	return EVBACKEND_LINUXAIO;
326	}
327
328	inline_size
329	void
330	linuxaio_destroy (EV_P)
331	{
332	linuxaio_free_iocbp (EV_A);
333	ev_io_destroy (linuxaio_ctx);
334	}
335
336	inline_size
337	void
338	linuxaio_fork (EV_P)
339	{
340	abort ();//D
341	}
342