1 /* Copyright (c) 2013 Nicira, Inc.
3 * Licensed under the Apache License, Version 2.0 (the "License");
4 * you may not use this file except in compliance with the License.
5 * You may obtain a copy of the License at:
7 * http://www.apache.org/licenses/LICENSE-2.0
9 * Unless required by applicable law or agreed to in writing, software
10 * distributed under the License is distributed on an "AS IS" BASIS,
11 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 * See the License for the specific language governing permissions and
13 * limitations under the License.
18 /* This implementation of the async-append.h interface uses the POSIX
19 * asynchronous I/O interface. */
21 #include "async-append.h"
29 #include "ovs-thread.h"
32 /* Maximum number of bytes of buffered data. */
33 enum { BUFFER_SIZE = 65536 };
35 /* Maximum number of aiocbs to use.
37 * aiocbs are big (144 bytes with glibc 2.11 on i386) so we try to allow for a
38 * reasonable number by basing the number we allocate on the amount of buffer
40 enum { MAX_CBS = ROUND_DOWN_POW2(BUFFER_SIZE / sizeof(struct aiocb)) };
41 BUILD_ASSERT_DECL(IS_POW2(MAX_CBS));
47 unsigned int aiocb_head, aiocb_tail;
53 static bool async_append_enabled;
56 async_append_enable(void)
58 assert_single_threaded();
59 forbid_forking("async i/o enabled");
60 async_append_enabled = true;
64 async_append_create(int fd)
66 struct async_append *ap;
68 ap = xmalloc(sizeof *ap);
70 ap->aiocbs = xmalloc(MAX_CBS * sizeof *ap->aiocbs);
71 ap->aiocb_head = ap->aiocb_tail = 0;
72 ap->buffer = xmalloc(BUFFER_SIZE);
73 byteq_init(&ap->byteq, ap->buffer, BUFFER_SIZE);
79 async_append_destroy(struct async_append *ap)
82 async_append_flush(ap);
90 async_append_is_full(const struct async_append *ap)
92 return (ap->aiocb_head - ap->aiocb_tail >= MAX_CBS
93 || byteq_is_full(&ap->byteq));
97 async_append_is_empty(const struct async_append *ap)
99 return byteq_is_empty(&ap->byteq);
103 async_append_wait(struct async_append *ap)
107 while (!async_append_is_empty(ap)) {
108 struct aiocb *aiocb = &ap->aiocbs[ap->aiocb_tail & (MAX_CBS - 1)];
109 int error = aio_error(aiocb);
111 if (error == EINPROGRESS) {
112 const struct aiocb *p = aiocb;
116 aio_suspend(&p, 1, NULL);
118 ignore(aio_return(aiocb));
120 byteq_advance_tail(&ap->byteq, aiocb->aio_nbytes);
127 async_append_write(struct async_append *ap, const void *data_, size_t size)
129 const uint8_t *data = data_;
131 if (!async_append_enabled) {
132 ignore(write(ap->fd, data, size));
141 while (async_append_is_full(ap)) {
142 async_append_wait(ap);
145 chunk = byteq_head(&ap->byteq);
146 chunk_size = byteq_headroom(&ap->byteq);
147 if (chunk_size > size) {
150 memcpy(chunk, data, chunk_size);
152 aiocb = &ap->aiocbs[ap->aiocb_head & (MAX_CBS - 1)];
153 memset(aiocb, 0, sizeof *aiocb);
154 aiocb->aio_fildes = ap->fd;
155 aiocb->aio_offset = 0;
156 aiocb->aio_buf = chunk;
157 aiocb->aio_nbytes = chunk_size;
158 aiocb->aio_sigevent.sigev_notify = SIGEV_NONE;
159 if (aio_write(aiocb) == -1) {
160 async_append_flush(ap);
161 ignore(write(ap->fd, data, size));
167 byteq_advance_head(&ap->byteq, chunk_size);
173 async_append_flush(struct async_append *ap)
175 while (!async_append_is_empty(ap)) {
176 async_append_wait(ap);