Re: [PATCH] vsock: avoid timeout for non-blocking accept() with empty backlog

[Stefano Garzarella <sgarzare@redhat.com>]

On Thu, Apr 02, 2026 at 04:30:20PM -0700, Laurence Rowe wrote:
>On Thu, Apr 2, 2026 at 12:22 PM Laurence Rowe <laurencerowe@gmail.com> wrote:
>>
>> On Thu, Apr 2, 2026 at 5:03 AM Stefano Garzarella <sgarzare@redhat.com> wrote:
>>
>> > >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.
>> >
>> > Not related to this patch, but should we do something similar (in
>> > another patch) also in vsock_connect() or doesn't matter since usually
>> > it's always blocking?
>>
>> Looking at vsock_connect it's not immediately obvious to me whether it
>> is affected
>> in the same way. I'll capture some ftraces and follow up after
>> updating this patch.
>
>This does not seem to be a problem for vsock_connect since it checks
>for `if (flags & O_NONBLOCK) {` in the while loop before calling
>`schedule_timeout`.
>
>Timings and ftraces:
>
>https://github.com/lrowe/linux-vsock-accept-timeout-investigation?tab=readme-ov-file#a-quick-look-at-connect

Thanks for checking and for the fix!
Stefano