mirror of /home/gitosis/repositories/libev.git
Marc Alexander Lehmann
4 years ago
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9c2c08ed07
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0ce071c104
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/*
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* libev linux aio fd activity backend |
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* |
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* Copyright (c) 2019 Marc Alexander Lehmann <libev@schmorp.de> |
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* All rights reserved. |
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* |
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* Redistribution and use in source and binary forms, with or without modifica- |
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* tion, are permitted provided that the following conditions are met: |
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* |
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* 1. Redistributions of source code must retain the above copyright notice, |
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* this list of conditions and the following disclaimer. |
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* |
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* 2. Redistributions in binary form must reproduce the above copyright |
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* notice, this list of conditions and the following disclaimer in the |
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* documentation and/or other materials provided with the distribution. |
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* |
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED |
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* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MER- |
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* CHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO |
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* EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPE- |
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* CIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, |
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; |
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* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, |
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* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTH- |
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* ERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED |
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* OF THE POSSIBILITY OF SUCH DAMAGE. |
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* |
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* Alternatively, the contents of this file may be used under the terms of |
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* the GNU General Public License ("GPL") version 2 or any later version, |
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* in which case the provisions of the GPL are applicable instead of |
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* the above. If you wish to allow the use of your version of this file |
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* only under the terms of the GPL and not to allow others to use your |
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* version of this file under the BSD license, indicate your decision |
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* by deleting the provisions above and replace them with the notice |
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* and other provisions required by the GPL. If you do not delete the |
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* provisions above, a recipient may use your version of this file under |
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* either the BSD or the GPL. |
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*/ |
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#include <sys/time.h> /* actually linux/time.h, but we must assume they are compatible */ |
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#include <linux/aio_abi.h> |
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/* we try to fill 4kn pages exactly.
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* the ring buffer header is 32 bytes, every io event is 32 bytes. |
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* the kernel takes the io event number, doubles it, adds 2, adds the ring buffer |
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* so the calculation below will use "exactly" 8kB for the ring buffer |
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*/ |
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#define EV_LINUXAIO_DEPTH (256 / 2 - 2 - 1) /* max. number of io events per batch */ |
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/*****************************************************************************/ |
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/* syscall wrapdadoop */ |
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#include <sys/syscall.h> /* no glibc wrappers */ |
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/* aio_abi.h is not verioned in any way, so we cannot test for its existance */ |
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#define IOCB_CMD_POLL 5 |
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/* taken from linux/fs/aio.c */ |
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#define AIO_RING_MAGIC 0xa10a10a1 |
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#define AIO_RING_INCOMPAT_FEATURES 0 |
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struct aio_ring |
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{ |
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unsigned id; /* kernel internal index number */ |
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unsigned nr; /* number of io_events */ |
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unsigned head; /* Written to by userland or by kernel. */ |
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unsigned tail; |
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unsigned magic; |
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unsigned compat_features; |
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unsigned incompat_features; |
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unsigned header_length; /* size of aio_ring */ |
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struct io_event io_events[0]; |
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}; |
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static int |
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ev_io_setup (unsigned nr_events, aio_context_t *ctx_idp) |
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{ |
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return syscall (SYS_io_setup, nr_events, ctx_idp); |
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} |
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static int |
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ev_io_destroy (aio_context_t ctx_id) |
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{ |
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return syscall (SYS_io_destroy, ctx_id); |
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} |
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static int |
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ev_io_submit (aio_context_t ctx_id, long nr, struct iocb *cbp[]) |
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{ |
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return syscall (SYS_io_submit, ctx_id, nr, cbp); |
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} |
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static int |
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ev_io_cancel (aio_context_t ctx_id, struct iocb *cbp, struct io_event *result) |
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{ |
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return syscall (SYS_io_cancel, ctx_id, cbp, result); |
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} |
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static int |
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ev_io_getevents (aio_context_t ctx_id, long min_nr, long nr, struct io_event *events, struct timespec *timeout) |
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{ |
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return syscall (SYS_io_getevents, ctx_id, min_nr, nr, events, timeout); |
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} |
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typedef void (*ev_io_cb) (long nr, struct io_event *events); |
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/*****************************************************************************/ |
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/* actual backed implementation */ |
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/* two iocbs for every fd, one for read, one for write */ |
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typedef struct aniocb |
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{ |
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struct iocb io; |
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/*int inuse;*/ |
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} *ANIOCBP; |
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inline_size |
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void |
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linuxaio_array_needsize_iocbp (ANIOCBP *base, int count) |
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{ |
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/* TODO: quite the overhead to allocate every iocb separately */ |
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while (count--) |
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{ |
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*base = (ANIOCBP)ev_malloc (sizeof (**base)); |
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memset (*base, 0, sizeof (**base)); |
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/* would be nice to initialize fd/data as well */ |
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(*base)->io.aio_lio_opcode = IOCB_CMD_POLL; |
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++base; |
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} |
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} |
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static void |
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linuxaio_free_iocbp (EV_P) |
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{ |
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while (linuxaio_iocbpmax--) |
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ev_free (linuxaio_iocbps [linuxaio_iocbpmax]); |
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linuxaio_iocbpmax = 0; |
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} |
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static void |
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linuxaio_modify (EV_P_ int fd, int oev, int nev) |
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{ |
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/* TODO: full zero initialize required? */ |
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array_needsize (ANIOCBP, linuxaio_iocbps, linuxaio_iocbpmax, fd + 1, linuxaio_array_needsize_iocbp); |
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struct aniocb *iocb = linuxaio_iocbps [fd]; |
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if (iocb->io.aio_buf) |
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ev_io_cancel (linuxaio_ctx, &iocb->io, (void *)0); |
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if (nev) |
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{ |
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iocb->io.aio_data = fd; |
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iocb->io.aio_fildes = fd; |
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iocb->io.aio_buf = |
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(nev & EV_READ ? POLLIN : 0) |
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| (nev & EV_WRITE ? POLLOUT : 0); |
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/* queue iocb up for io_submit */ |
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/* this assumes we only ever get one call per fd per loop iteration */ |
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++linuxaio_submitcnt; |
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array_needsize (struct iocb *, linuxaio_submits, linuxaio_submitmax, linuxaio_submitcnt, array_needsize_noinit); |
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linuxaio_submits [linuxaio_submitcnt - 1] = &iocb->io; |
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} |
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} |
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static void |
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linuxaio_parse_events (EV_P_ struct io_event *ev, int nr) |
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{ |
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while (nr) |
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{ |
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int fd = ev->data; |
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int res = ev->res; |
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assert (("libev: iocb fd must be in-bounds", fd >= 0 && fd < anfdxmax)); |
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/* linux aio is oneshot: rearm fd */ |
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linuxaio_iocbps [fd]->io.aio_buf = 0; |
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anfds [fd].events = 0; |
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fd_change (EV_A_ fd, 0); |
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/* feed events, we do not expect or handle POLLNVAL */ |
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if (ecb_expect_false (res & POLLNVAL)) |
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fd_kill (EV_A_ fd); |
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else |
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fd_event ( |
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EV_A_ |
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fd, |
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(res & (POLLOUT | POLLERR | POLLHUP) ? EV_WRITE : 0) |
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| (res & (POLLIN | POLLERR | POLLHUP) ? EV_READ : 0) |
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); |
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--nr; |
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++ev; |
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} |
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} |
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/* get any events from ringbuffer, return true if any were handled */ |
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static int |
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linuxaio_get_events_from_ring (EV_P) |
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{ |
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struct aio_ring *ring = (struct aio_ring *)linuxaio_ctx; |
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ECB_MEMORY_FENCE_ACQUIRE; |
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unsigned head = ring->head; |
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unsigned tail = *(volatile unsigned *)&ring->tail; |
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if (ring->magic != AIO_RING_MAGIC |
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|| ring->incompat_features != AIO_RING_INCOMPAT_FEATURES |
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|| ring->header_length != sizeof (struct aio_ring) /* TODO: or use it to find io_event[0]? */ |
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|| head == tail) |
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return 0; |
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/* parse all available events, but only once, to avoid starvation */ |
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if (tail > head) /* normal case around */ |
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linuxaio_parse_events (EV_A_ ring->io_events + head, tail - head); |
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else |
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{ |
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/* wrapped around */ |
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linuxaio_parse_events (EV_A_ ring->io_events + head, ring->nr - head); |
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linuxaio_parse_events (EV_A_ ring->io_events, tail); |
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} |
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ring->head = tail; |
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return 1; |
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} |
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/* read at least one event from kernel, or timeout */ |
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inline_size |
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void |
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linuxaio_get_events (EV_P_ ev_tstamp timeout) |
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{ |
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struct timespec ts; |
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struct io_event ioev; |
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int res; |
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if (linuxaio_get_events_from_ring (EV_A)) |
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return; |
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/* no events, so wait for at least one, then poll ring buffer again */ |
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/* this degraded to one event per loop iteration */ |
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/* if the ring buffer changes layout, but so be it */ |
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ts.tv_sec = (long)timeout; |
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ts.tv_nsec = (long)((timeout - ts.tv_sec) * 1e9); |
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res = ev_io_getevents (linuxaio_ctx, 1, 1, &ioev, &ts); |
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if (res < 0) |
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ev_syserr ("(libev) io_getevents"); |
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else if (res) |
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{ |
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/* at least one event received, handle it and any remaining ones in the ring buffer */ |
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linuxaio_parse_events (EV_A_ &ioev, 1); |
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linuxaio_get_events_from_ring (EV_A); |
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} |
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} |
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static void |
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linuxaio_poll (EV_P_ ev_tstamp timeout) |
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{ |
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int submitted; |
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/* first phase: submit new iocbs */ |
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/* io_submit might return less than the requested number of iocbs */ |
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/* this is, afaics, only because of errors, but we go by the book and use a loop, */ |
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/* which allows us to pinpoint the errornous iocb */ |
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for (submitted = 0; submitted < linuxaio_submitcnt; ) |
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{ |
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int res = ev_io_submit (linuxaio_ctx, linuxaio_submitcnt - submitted, linuxaio_submits + submitted); |
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if (res < 0) |
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if (errno == EAGAIN) |
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{ |
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/* This happens when the ring buffer is full, at least. I assume this means
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* that the event was queued synchronously during io_submit, and thus |
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* the buffer overflowd. |
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* In this case, we just try next loop iteration. |
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*/ |
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memcpy (linuxaio_submits, linuxaio_submits + submitted, (linuxaio_submitcnt - submitted) * sizeof (*linuxaio_submits)); |
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linuxaio_submitcnt -= submitted; |
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timeout = 0; |
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break; |
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} |
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else |
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/* TODO: we get EAGAIN when the ring buffer is full for some reason */ |
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/* TODO: should we always just try next time? */ |
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ev_syserr ("(libev) io_submit"); |
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submitted += res; |
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} |
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linuxaio_submitcnt = 0; |
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/* second phase: fetch and parse events */ |
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linuxaio_get_events (EV_A_ timeout); |
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} |
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inline_size |
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int |
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linuxaio_init (EV_P_ int flags) |
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{ |
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/* would be great to have a nice test for IOCB_CMD_POLL instead */ |
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if (ev_linux_version () < 0x041200) /* 4.18 introduced IOCB_CMD_POLL */ |
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return 0; |
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if (ev_io_setup (EV_LINUXAIO_DEPTH, &linuxaio_ctx) < 0) |
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return 0; |
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backend_modify = linuxaio_modify; |
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backend_poll = linuxaio_poll; |
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linuxaio_iocbpmax = 0; |
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linuxaio_iocbps = 0; |
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linuxaio_submits = 0; |
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linuxaio_submitmax = 0; |
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linuxaio_submitcnt = 0; |
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return EVBACKEND_LINUXAIO; |
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} |
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inline_size |
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void |
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linuxaio_destroy (EV_P) |
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{ |
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linuxaio_free_iocbp (EV_A); |
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ev_io_destroy (linuxaio_ctx); |
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} |
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inline_size |
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void |
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linuxaio_fork (EV_P) |
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{ |
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abort ();//D
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} |
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