From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nigel Cunningham Subject: Re: [PATCH 12/15] swap: do not send discards as barriers Date: Sun, 22 Aug 2010 22:20:16 +1000 Message-ID: <4C711600.9000407@tuxonice.net> References: <20100818093432.646633424@bombadil.infradead.org> <20100818093502.062639046@bombadil.infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Christoph Hellwig , tj@kernel.org, chris.mason@oracle.com, swhiteho@redhat.com, konishi.ryusuke@lab.ntt.co.jp, tytso@mit.edu, jack@suse.cz, hirofumi@mail.parknet.co.jp, mfasheh@suse.com, joel.becker@oracle.com, linux-fsdevel@vger.kernel.org To: Hugh Dickins Return-path: Received: from tuxonice.net ([74.207.252.127]:34037 "EHLO mail.tuxonice.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752428Ab0HVMUV (ORCPT ); Sun, 22 Aug 2010 08:20:21 -0400 In-Reply-To: Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Hi. On 19/08/10 13:47, Hugh Dickins wrote: > On Wed, 18 Aug 2010, Christoph Hellwig wrote: > >> The swap code already uses synchronous discards, no need to add I/O barriers. >> >> Signed-off-by: Christoph Hellwig > > Acked-by: Hugh Dickins > > (though if you happened to respin, I'd be be glad for those newlines > between GFP_KERNEL, BLKDEV_IFL_WAIT to go away now) > > This patch could go in any time now: I may want to push it in and > get it to 35-stable, because it certainly helps against the swap > discard regression that Nigel reported (though I've not yet seen > his numbers with this). However, I don't think it eliminates the > regression, so I've more testing and experimenting to do before > deciding about it - the right answer may just be to disable swap > discard, as you asked for long ago. That's correct. The patch reduces the pause from minutes to a matter of seconds (with 4GB of swap), but it is still there (there was previously no discernable delay). Tested-by: Nigel Cunningham Regards, Nigel