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vsock: avoid timeout for non-blocking accept() with empty backlog

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A common pattern in epoll network servers is to eagerly accept all
pending connections from the non-blocking listening socket after
epoll_wait indicates the socket is ready by calling accept in a loop
until EAGAIN is returned indicating that the backlog is empty.

Scheduling a timeout for a non-blocking accept with an empty backlog
meant AF_VSOCK sockets used by epoll network servers incurred hundreds
of microseconds of additional latency per accept loop compared to
AF_INET or AF_UNIX sockets.

Signed-off-by: Laurence Rowe <laurencerowe@gmail.com>
Reviewed-by: Bobby Eshleman <bobbyeshleman@meta.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Link: https://patch.msgid.link/20260402204918.130395-1-laurencerowe@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Laurence Rowe
2026-04-02 13:49:18 -07:00
committed by Jakub Kicinski
parent c8eee00c0f
commit 98f28d8d6e
1 changed files with 6 additions and 9 deletions
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15
net/vmw_vsock/af_vsock.c
View File

@@ -1864,10 +1864,10 @@ static int vsock_accept(struct socket *sock, struct socket *newsock,
* created upon connection establishment.
*/
timeout = sock_rcvtimeo(listener, arg->flags & O_NONBLOCK);
prepare_to_wait(sk_sleep(listener), &wait, TASK_INTERRUPTIBLE);
while ((connected = vsock_dequeue_accept(listener)) == NULL &&
listener->sk_err == 0) {
listener->sk_err == 0 && timeout != 0) {
prepare_to_wait(sk_sleep(listener), &wait, TASK_INTERRUPTIBLE);
release_sock(listener);
timeout = schedule_timeout(timeout);
finish_wait(sk_sleep(listener), &wait);
@@ -1876,17 +1876,14 @@ static int vsock_accept(struct socket *sock, struct socket *newsock,
if (signal_pending(current)) {
err = sock_intr_errno(timeout);
goto out;
} else if (timeout == 0) {
err = -EAGAIN;
goto out;
}
prepare_to_wait(sk_sleep(listener), &wait, TASK_INTERRUPTIBLE);
}
finish_wait(sk_sleep(listener), &wait);
if (listener->sk_err)
if (listener->sk_err) {
err = -listener->sk_err;
} else if (!connected) {
err = -EAGAIN;
}
if (connected) {
sk_acceptq_removed(listener);