netdev - Re: [PATCH] poll: Avoid extra wakeups

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Message-ID: <87ab60rh8t.fsf@basil.nowhere.org>
Date:	Tue, 28 Apr 2009 16:21:38 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Eric Dumazet <dada1@...mosbay.com>
Cc:	David Miller <davem@...emloft.net>, cl@...ux.com,
	jesse.brandeburg@...el.com, netdev@...r.kernel.org,
	haoki@...hat.com, mchan@...adcom.com, davidel@...ilserver.org
Subject: Re: [PATCH] poll: Avoid extra wakeups

Eric Dumazet <dada1@...mosbay.com> writes:
>
> 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.

I wonder if the key could be used for more state. For example if you
two processes are in recvmsg() on a socket and there's only a single
packet incoming we only need to wake up the first waiter.  Could that
be done with keys too?

> 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.

I'm late, but: very cool patch too.

Acked-by: Andi Kleen <ak@...ux.intel.com>

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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