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

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Message-ID: <20090429092240.GA30403@elte.hu>
Date:	Wed, 29 Apr 2009 11:22:40 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Eric Dumazet <dada1@...mosbay.com>,
	linux kernel <linux-kernel@...r.kernel.org>,
	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 in select/poll


* Andi Kleen <andi@...stfloor.org> wrote:

> > Seems that this is a virtuous patch even though Christoph is struggling
> > a bit to test it?
> 
> The main drawback is that the select/poll data structures will get 
> larger. That could cause regression in theory. [...]

Current size of struct poll_table_entry is 0x38 on 64-bit kernels. 
Adding the key will make it 0x40 - which is not only a power of two 
but also matches cache line size on most modern CPUs.

So the size of this structure is ideal now and arithmetics on the 
poll table have become simpler as well.

So the patch has my ack:

  Acked-by: Ingo Molnar <mingo@...e.hu>

	Ingo
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