linux-kernel - Re: [PATCH] poll: Avoid extra wakeups in select/poll

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Date:	Wed, 29 Apr 2009 08:53:52 -0700 (PDT)
From:	Davide Libenzi <davidel@...ilserver.org>
To:	Eric Dumazet <dada1@...mosbay.com>
cc:	Ingo Molnar <mingo@...e.hu>,
	linux kernel <linux-kernel@...r.kernel.org>,
	Andi Kleen <andi@...stfloor.org>,
	David Miller <davem@...emloft.net>, cl@...ux.com,
	jesse.brandeburg@...el.com, netdev@...r.kernel.org,
	haoki@...hat.com, mchan@...adcom.com
Subject: Re: [PATCH] poll: Avoid extra wakeups in select/poll

On Wed, 29 Apr 2009, Eric Dumazet wrote:

> [PATCH] poll: Avoid extra wakeups in select/poll
> 
> After introduction of keyed wakeups Davide Libenzi did on epoll, we
> are able to avoid spurious wakeups in poll()/select() code too.
> 
> For example, typical use of poll()/select() is to wait for incoming
> network frames on many sockets. But TX completion for UDP/TCP 
> frames call sock_wfree() which in turn schedules thread.
> 
> When scheduled, thread does a full scan of all polled fds and
> can sleep again, because nothing is really available. If number
> of fds is large, this cause significant load.
> 
> This patch makes select()/poll() aware of keyed wakeups and
> useless wakeups are avoided. This reduces number of context
> switches by about 50% on some setups, and work performed
> by sofirq handlers.

Looks fine to me Eric ...

Acked-by: Davide Libenzi <davidel@...ilserver.org>


- Davide


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