* Re: Fw: Re: [Patch][RFC] epoll and half closed TCP connections
[not found] <20030713070352.3f21a9f8.davem@redhat.com>
@ 2003-07-14 17:39 ` kuznet
2003-07-14 18:25 ` Davide Libenzi
0 siblings, 1 reply; 2+ messages in thread
From: kuznet @ 2003-07-14 17:39 UTC (permalink / raw)
To: David S. Miller; +Cc: jmorris, jamie, linux-kernel
Hello!
> it looks as though _every_ TCP ACK you receive will cause epoll to wake up
> a task which is interested in _any_ socket events,
This is not quite true. sk->write_space() is called only after write
queue is full, and it is exactly one wakeup until the next overflow.
But, actually, yes, it is right observation: one wait queue for all
the socket events is painful. Note, that with current poll() improvements
are suboptimal, tcp_poll() does not know _what_ this poll polls for,
so it has to stand in all the wait queues. The same thing kills lots
of possible improvements.
> further, we might as well admit that POLLHUP should be called
> POLLWRHUP.)
No, really. POLLHUP=POLLRDHUP&POLLWRHUP, plus POLLHUP is unmaskable event.
Yes, SVR4 screwed up its semantics in such extent that it is mostly
meaningless.
Alexey
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: Fw: Re: [Patch][RFC] epoll and half closed TCP connections
2003-07-14 17:39 ` Fw: Re: [Patch][RFC] epoll and half closed TCP connections kuznet
@ 2003-07-14 18:25 ` Davide Libenzi
0 siblings, 0 replies; 2+ messages in thread
From: Davide Libenzi @ 2003-07-14 18:25 UTC (permalink / raw)
To: kuznet; +Cc: David S. Miller, jmorris, jamie, Linux Kernel Mailing List
On Mon, 14 Jul 2003 kuznet@ms2.inr.ac.ru wrote:
> > it looks as though _every_ TCP ACK you receive will cause epoll to wake up
> > a task which is interested in _any_ socket events,
>
> This is not quite true. sk->write_space() is called only after write
> queue is full, and it is exactly one wakeup until the next overflow.
>
> But, actually, yes, it is right observation: one wait queue for all
> the socket events is painful. Note, that with current poll() improvements
> are suboptimal, tcp_poll() does not know _what_ this poll polls for,
> so it has to stand in all the wait queues. The same thing kills lots
> of possible improvements.
Indeed. This can be improved though, with some serious work. The poll(2)
and epoll caller supply events he is interested in. We could have
poll_wait() (and f_op->poll()) to accept an events parameter so that the
f_op->poll() code can drop inside separate wait queue depending on what
the caller is waiting for.
- Davide
^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2003-07-14 18:18 UTC | newest]
Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
[not found] <20030713070352.3f21a9f8.davem@redhat.com>
2003-07-14 17:39 ` Fw: Re: [Patch][RFC] epoll and half closed TCP connections kuznet
2003-07-14 18:25 ` Davide Libenzi
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).