linux-kernel - Re: [PATCH] af_unix: optimize unix_dgram

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Date:	Sat, 30 Oct 2010 10:45:37 -0700 (PDT)
From:	Davide Libenzi <davidel@...ilserver.org>
To:	Eric Dumazet <eric.dumazet@...il.com>
cc:	Davide Libenzi <davidel@...ilserver.org>,
	Alban Crequy <alban.crequy@...labora.co.uk>,
	"David S. Miller" <davem@...emloft.net>,
	Stephen Hemminger <shemminger@...tta.com>,
	Cyrill Gorcunov <gorcunov@...nvz.org>,
	Alexey Dobriyan <adobriyan@...il.com>, netdev@...r.kernel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Pauli Nieminen <pauli.nieminen@...labora.co.uk>,
	Rainer Weikusat <rweikusat@...gmbh.com>
Subject: Re: [PATCH] af_unix: optimize unix_dgram_poll()

On Sat, 30 Oct 2010, Eric Dumazet wrote:

> Le vendredi 29 octobre 2010 à 13:46 -0700, Davide Libenzi a écrit :
> 
> > Also, why not using the existing wait->key instead of adding a poll2()?
> 
> Indeed, if wait is not null, we have in wait->key the interest of
> poller. If a particular poll() function is expensive, it can test these
> bits.
> 
> Thanks !
> 
> Note: I chose the 'goto skip_write' to make this patch really obvious.

Plain agreement on th patch, and I understand the indent overflow 
concerns, but why not ...

	/*
	 * No write status requested, avoid expensive OUT tests.
	 */
	if (wait && !(wait->key & (POLLWRBAND | POLLWRNORM | POLLOUT)))
		return mask

The write-test code is the last one we do anyway.


- Davide