From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [PATCH] [1/2] Optimization for touch_atime Date: Tue, 7 Jul 2009 06:49:14 -0400 Message-ID: <20090707104914.GA23619@infradead.org> References: <20090706924.495556466@firstfloor.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: viro@zeniv.linux.org.uk, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org To: Andi Kleen Return-path: Received: from bombadil.infradead.org ([18.85.46.34]:49660 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753255AbZGGKtM (ORCPT ); Tue, 7 Jul 2009 06:49:12 -0400 Content-Disposition: inline In-Reply-To: <20090706924.495556466@firstfloor.org> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Mon, Jul 06, 2009 at 09:24:46PM +0200, Andi Kleen wrote: > > Some benchmark testing shows touch_atime to be high up in profile > logs for IO intensive workloads. Most likely that's due to the lock > in mnt_want_write(). Unfortunately touch_atime first takes the lock, > and then does all the other tests that could avoid atime updates (like > noatime or relatime). > > Do it the other way round -- first try to avoid the update and only > then if that didn't succeed take the lock. That works because none of > the atime avoidance tests rely on locking. > > This also eliminates a goto. > > Signed-off-by: Andi Kleen Looks good to me.