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unix: avoid extra read, short-circuit on POLLHUP

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Avoid going through an extra alloc_cb -> read() -> read_cb cycle when
the POLLHUP flag is set because we know the next read() will hit EOF.

Fixes #803.
This commit is contained in:
Ben Noordhuis 2013-05-25 22:06:26 +02:00
parent fc6a2ad24f
commit 442d11d618
3 changed files with 63 additions and 33 deletions
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2
include/uv.h
View File

@ -349,6 +349,8 @@ typedef uv_buf_t (*uv_alloc_cb)(uv_handle_t* handle, size_t suggested_size);
* Trying to read from the stream again is undefined.
*
* The callee is responsible for freeing the buffer, libuv does not reuse it.
* The buffer may be a null buffer (where buf.base=NULL and buf.len=0) on EOF
* or error.
*/
typedef void (*uv_read_cb)(uv_stream_t* stream, ssize_t nread, uv_buf_t buf);

24
src/unix/internal.h
View File

@ -99,17 +99,19 @@
/* handle flags */
enum {
UV_CLOSING = 0x01, /* uv_close() called but not finished. */
UV_CLOSED = 0x02, /* close(2) finished. */
UV_STREAM_READING = 0x04, /* uv_read_start() called. */
UV_STREAM_SHUTTING = 0x08, /* uv_shutdown() called but not complete. */
UV_STREAM_SHUT = 0x10, /* Write side closed. */
UV_STREAM_READABLE = 0x20, /* The stream is readable */
UV_STREAM_WRITABLE = 0x40, /* The stream is writable */
UV_STREAM_BLOCKING = 0x80, /* Synchronous writes. */
UV_TCP_NODELAY = 0x100, /* Disable Nagle. */
UV_TCP_KEEPALIVE = 0x200, /* Turn on keep-alive. */
UV_TCP_SINGLE_ACCEPT = 0x400 /* Only accept() when idle. */
UV_CLOSING = 0x01, /* uv_close() called but not finished. */
UV_CLOSED = 0x02, /* close(2) finished. */
UV_STREAM_READING = 0x04, /* uv_read_start() called. */
UV_STREAM_SHUTTING = 0x08, /* uv_shutdown() called but not complete. */
UV_STREAM_SHUT = 0x10, /* Write side closed. */
UV_STREAM_READABLE = 0x20, /* The stream is readable */
UV_STREAM_WRITABLE = 0x40, /* The stream is writable */
UV_STREAM_BLOCKING = 0x80, /* Synchronous writes. */
UV_STREAM_READ_PARTIAL = 0x100, /* read(2) read less than requested. */
UV_STREAM_READ_EOF = 0x200, /* read(2) read EOF. */
UV_TCP_NODELAY = 0x400, /* Disable Nagle. */
UV_TCP_KEEPALIVE = 0x800, /* Turn on keep-alive. */
UV_TCP_SINGLE_ACCEPT = 0x1000 /* Only accept() when idle. */
};
/* core */

70
src/unix/stream.c
View File

@ -930,6 +930,27 @@ static uv_handle_type uv__handle_type(int fd) {
}
static void uv__stream_read_cb(uv_stream_t* stream,
int status,
uv_buf_t buf,
uv_handle_type type) {
if (stream->read_cb != NULL)
stream->read_cb(stream, status, buf);
else
stream->read2_cb((uv_pipe_t*) stream, status, buf, type);
}
static void uv__stream_eof(uv_stream_t* stream, uv_buf_t buf) {
stream->flags |= UV_STREAM_READ_EOF;
uv__io_stop(stream->loop, &stream->io_watcher, UV__POLLIN);
if (!uv__io_active(&stream->io_watcher, UV__POLLOUT))
uv__handle_stop(stream);
uv__set_artificial_error(stream->loop, UV_EOF);
uv__stream_read_cb(stream, -1, buf, UV_UNKNOWN_HANDLE);
}
static void uv__read(uv_stream_t* stream) {
uv_buf_t buf;
ssize_t nread;
@ -938,6 +959,8 @@ static void uv__read(uv_stream_t* stream) {
char cmsg_space[64];
int count;
stream->flags &= ~UV_STREAM_READ_PARTIAL;
/* Prevent loop starvation when the data comes in as fast as (or faster than)
* we can read it. XXX Need to rearm fd if we switch to edge-triggered I/O.
*/
@ -979,15 +1002,6 @@ static void uv__read(uv_stream_t* stream) {
while (nread < 0 && errno == EINTR);
}
#define INVOKE_READ_CB(stream, status, buf, type) \
do { \
if ((stream)->read_cb != NULL) \
(stream)->read_cb((stream), (status), (buf)); \
else \
(stream)->read2_cb((uv_pipe_t*) (stream), (status), (buf), (type)); \
} \
while (0)
if (nread < 0) {
/* Error */
if (errno == EAGAIN || errno == EWOULDBLOCK) {
@ -996,22 +1010,17 @@ static void uv__read(uv_stream_t* stream) {
uv__io_start(stream->loop, &stream->io_watcher, UV__POLLIN);
}
uv__set_sys_error(stream->loop, EAGAIN);
INVOKE_READ_CB(stream, 0, buf, UV_UNKNOWN_HANDLE);
uv__stream_read_cb(stream, 0, buf, UV_UNKNOWN_HANDLE);
} else {
/* Error. User should call uv_close(). */
uv__set_sys_error(stream->loop, errno);
INVOKE_READ_CB(stream, -1, buf, UV_UNKNOWN_HANDLE);
uv__stream_read_cb(stream, -1, buf, UV_UNKNOWN_HANDLE);
assert(!uv__io_active(&stream->io_watcher, UV__POLLIN) &&
"stream->read_cb(status=-1) did not call uv_close()");
}
return;
} else if (nread == 0) {
/* EOF */
uv__io_stop(stream->loop, &stream->io_watcher, UV__POLLIN);
if (!uv__io_active(&stream->io_watcher, UV__POLLOUT))
uv__handle_stop(stream);
uv__set_artificial_error(stream->loop, UV_EOF);
INVOKE_READ_CB(stream, -1, buf, UV_UNKNOWN_HANDLE);
uv__stream_eof(stream, buf);
return;
} else {
/* Successful read */
@ -1062,6 +1071,7 @@ static void uv__read(uv_stream_t* stream) {
/* Return if we didn't fill the buffer, there is no more data to read. */
if (nread < buflen) {
stream->flags |= UV_STREAM_READ_PARTIAL;
return;
}
}
@ -1110,17 +1120,33 @@ static void uv__stream_io(uv_loop_t* loop, uv__io_t* w, unsigned int events) {
return;
}
if (events & (UV__POLLIN | UV__POLLERR | UV__POLLHUP)) {
assert(uv__stream_fd(stream) >= 0);
assert(uv__stream_fd(stream) >= 0);
/* Ignore POLLHUP here. Even it it's set, there may still be data to read. */
if (events & (UV__POLLIN | UV__POLLERR))
uv__read(stream);
if (uv__stream_fd(stream) == -1)
return; /* read_cb closed stream. */
if (uv__stream_fd(stream) == -1)
return; /* read_cb closed stream. */
/* Short-circuit iff POLLHUP is set, the user is still interested in read
* events and uv__read() reported a partial read but not EOF. If the EOF
* flag is set, uv__read() called read_cb with err=UV_EOF and we don't
* have to do anything. If the partial read flag is not set, we can't
* report the EOF yet because there is still data to read.
*/
if ((events & UV__POLLHUP) &&
(stream->flags & UV_STREAM_READING) &&
(stream->flags & UV_STREAM_READ_PARTIAL) &&
!(stream->flags & UV_STREAM_READ_EOF)) {
uv_buf_t buf = { NULL, 0 };
uv__stream_eof(stream, buf);
}
if (uv__stream_fd(stream) == -1)
return; /* read_cb closed stream. */
if (events & UV__POLLOUT) {
assert(uv__stream_fd(stream) >= 0);
uv__write(stream);
uv__write_callbacks(stream);
}