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

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Date:	Tue, 28 Apr 2009 16:58:36 +0200
From:	Eric Dumazet <dada1@...mosbay.com>
To:	Andi Kleen <andi@...stfloor.org>
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

Andi Kleen a écrit :
> 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?

I am not sure its possible. I'll take a look.

> 
>> 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>

Thanks, I am going to send it again on lkml this time :)

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