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Avoid channel writev() when there is nothing to write

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This commit is contained in:
Matt Johnston 2015-03-21 22:43:08 +08:00
parent 275611fbaa
commit ef20b9ff7a
1 changed files with 10 additions and 1 deletions
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11
common-channel.c
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@ -473,6 +473,14 @@ static void writechannel(struct Channel* channel, int fd, circbuffer *cbuf,
io_count++; io_count++;
} }
if (io_count == 0) {
/* writechannel may sometimes be called twice in a main loop iteration.
From common_recv_msg_channel_data() then channelio().
The second call may not have any data to write, so we just return. */
TRACE(("leave writechannel, no data"))
return;
}
if (morelen) { if (morelen) {
/* Default return value, none consumed */ /* Default return value, none consumed */
*morelen = 0; *morelen = 0;
@ -482,7 +490,7 @@ static void writechannel(struct Channel* channel, int fd, circbuffer *cbuf,
if (written < 0) { if (written < 0) {
if (errno != EINTR && errno != EAGAIN) { if (errno != EINTR && errno != EAGAIN) {
TRACE(("errno %d", errno)) TRACE(("channel IO write error fd %d %s", fd, strerror(errno)))
close_chan_fd(channel, fd, SHUT_WR); close_chan_fd(channel, fd, SHUT_WR);
} }
} else { } else {
@ -830,6 +838,7 @@ void common_recv_msg_channel_data(struct Channel *channel, int fd,
channel->recvwindow -= datalen; channel->recvwindow -= datalen;
dropbear_assert(channel->recvwindow <= opts.recv_window); dropbear_assert(channel->recvwindow <= opts.recv_window);
/* Attempt to write the data immediately without having to put it in the circular buffer */
consumed = datalen; consumed = datalen;
writechannel(channel, fd, cbuf, buf_getptr(ses.payload, datalen), &consumed); writechannel(channel, fd, cbuf, buf_getptr(ses.payload, datalen), &consumed);