From: Eric Wong <normalperson@yhbt.net>
To: Ingo Molnar <mingo@kernel.org>
Cc: Jason Baron <jbaron@akamai.com>,
peterz@infradead.org, mingo@redhat.com, viro@zeniv.linux.org.uk,
akpm@linux-foundation.org, davidel@xmailserver.org,
mtk.manpages@gmail.com, linux-kernel@vger.kernel.org,
linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>,
Linus Torvalds <torvalds@linux-foundation.org>,
Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: [PATCH v2 2/2] epoll: introduce EPOLLEXCLUSIVE and EPOLLROUNDROBIN
Date: Wed, 18 Feb 2015 22:18:08 +0000 [thread overview]
Message-ID: <20150218221808.GA3799@dcvr.yhbt.net> (raw)
In-Reply-To: <20150218175123.GA31878@gmail.com>
Ingo Molnar <mingo@kernel.org> wrote:
>
> * Ingo Molnar <mingo@kernel.org> wrote:
>
> > > [...] However, I think the userspace API change is less
> > > clear since epoll_wait() doesn't currently have an
> > > 'input' events argument as epoll_ctl() does.
> >
> > ... but the change would be a bit clearer and somewhat
> > more flexible: LIFO or FIFO queueing, right?
> >
> > But having the queueing model as part of the epoll
> > context is a legitimate approach as well.
>
> Btw., there's another optimization that the networking code
> already does when processing incoming packets: waking up a
> thread on the local CPU, where the wakeup is running.
>
> Doing the same on epoll would have real scalability
> advantages where incoming events are IRQ driven and are
> distributed amongst multiple CPUs.
Right. One thing in the back of my mind has been to have CPU
affinity for epoll. Either having everything in an epoll set
favor a certain CPU or even having affinity down to the epitem
level (so concurrent epoll_wait callers end up favoring the
same epitems).
I'm not convinced this series is worth doing without a
comparison against my previous suggestion to use a dedicated
thread which only makes blocking accept4 + EPOLL_CTL_ADD calls.
The majority of epoll events in a typical server should not be
for listen sockets, so I'd rather not bloat existing code paths
for them. For web servers nowadays, the benefits of maintaining
long-lived connections to avoid handshakes is even more
beneficial with increasing HTTPS and HTTP2 adoption; so
listen socket events should become less common.
next prev parent reply other threads:[~2015-02-18 22:18 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-02-17 19:33 [PATCH v2 0/2] Add epoll round robin wakeup mode Jason Baron
2015-02-17 19:33 ` [PATCH v2 1/2] sched/wait: add " Jason Baron
2015-02-17 19:33 ` [PATCH v2 2/2] epoll: introduce EPOLLEXCLUSIVE and EPOLLROUNDROBIN Jason Baron
2015-02-18 8:07 ` Ingo Molnar
2015-02-18 15:42 ` Jason Baron
2015-02-18 16:33 ` Ingo Molnar
2015-02-18 17:38 ` Jason Baron
2015-02-18 17:45 ` Ingo Molnar
2015-02-18 17:51 ` Ingo Molnar
2015-02-18 22:18 ` Eric Wong [this message]
2015-02-19 3:26 ` Jason Baron
2015-02-22 0:24 ` Eric Wong
2015-02-25 15:48 ` Jason Baron
2015-02-18 23:12 ` Andy Lutomirski
[not found] ` <CAPh34mcPNQELwZCDTHej+HK=bpWgJ=jb1LeCtKoUHVgoDJOJoQ@mail.gmail.com>
2015-02-27 22:24 ` Jason Baron
2015-02-17 19:46 ` [PATCH v2 0/2] Add epoll round robin wakeup mode Andy Lutomirski
2015-02-17 20:33 ` Jason Baron
2015-02-17 21:09 ` Andy Lutomirski
2015-02-18 3:15 ` Jason Baron
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