From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Mason Subject: Re: Aggregating discard requests in the filesystem Date: Mon, 10 Nov 2008 15:44:23 -0500 Message-ID: <1226349863.10966.1.camel@think.oraclecorp.com> References: <4913028B.6010405@redhat.com> <20081110203915.GP15439@parisc-linux.org> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Cc: Ric Wheeler , David Woodhouse , James Bottomley , linux-scsi@vger.kernel.org, linux-fsdevel@vger.kernel.org, Black_David@emc.com, "Martin K. Petersen" , Tom Coughlan , Jens Axboe , Dave Chinner To: Matthew Wilcox Return-path: Received: from rcsinet13.oracle.com ([148.87.113.125]:18813 "EHLO rgminet13.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754333AbYKJUpB (ORCPT ); Mon, 10 Nov 2008 15:45:01 -0500 In-Reply-To: <20081110203915.GP15439@parisc-linux.org> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Mon, 2008-11-10 at 13:39 -0700, Matthew Wilcox wrote: > On Thu, Nov 06, 2008 at 09:43:23AM -0500, Ric Wheeler wrote: > > I have been thinking about whether or not we can (and should) do > > anything more than our current best effort to send down large chunks > > (note that the "chunk" size can range from reasonable sizes like 8KB or > > so up to close to 1MB!). > > One of the proposals in this thread (that has got buried somewhere) was > to expand any discard request sent down from the filesystem to encompass > all the adjacent free space. I've checked with our SSD people and > they're fine with this idea. > > dwmw2 says "it isn't actually that hard in FAT" and then interjects some > personal opinion about this solution ;-) > > Is it hard in XFS? btrfs? ext2? Does anyone have a problem with this > as a solution? > Btrfs needs some extra checking to make sure the extents really are free (and won't magically reappear after a crash), but it is at least possible. -chris