Re: [PATCH 0/3] MR617: server: Always prefer synchronous I/O in nonblocking mode. (#53486)

[Jin-oh Kang]

On Fri, Aug 12, 2022, 12:49 AM Jin-oh Kang  wrote:
> On Thu, Aug 11, 2022, 3:02 AM Zebediah Figura (she/her) <
> [e-mail]> wrote:
> > Doesn't this mean that we can get POLLOUT from the host but then be
> > unable to write data? That sounds like a spec violation.
>
> Unset POLLOUT does not necessarily imply that sendmsg() will block. On
> Linux (as of v5.19), POLLOUT is signaled on a connected TCP socket (that
> has not shut down) only if sk_wmem_queued is at least two thirds of
> sk_sndbuf (see __sk_stream_is_writeable). In contrast, sendmsg() will
> happily accept however much buffer space is left.

s/at least/at most/g.  Also modulo rounding error in sk_stream_min_wspace.
>