From: Greg Freemyer Subject: Re: Ext4: batched discard support Date: Mon, 19 Apr 2010 13:58:20 -0400 Message-ID: References: <1271674527-2977-1-git-send-email-lczerner@redhat.com> <4BCC8511.2070402@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Lukas Czerner , linux-ext4@vger.kernel.org, Jeff Moyer , Edward Shishkin , Eric Sandeen , Ric Wheeler , Mark Lord To: Eric Sandeen Return-path: Received: from mail-pw0-f46.google.com ([209.85.160.46]:34006 "EHLO mail-pw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753292Ab0DSR6U convert rfc822-to-8bit (ORCPT ); Mon, 19 Apr 2010 13:58:20 -0400 Received: by pwj9 with SMTP id 9so3588914pwj.19 for ; Mon, 19 Apr 2010 10:58:20 -0700 (PDT) In-Reply-To: <4BCC8511.2070402@redhat.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Mon, Apr 19, 2010 at 12:30 PM, Eric Sandeen wro= te: > Greg Freemyer wrote: >> Adding Mark Lord in cc. >> >> He wrote a preliminary discard solution last summer. =A0I'm not sure= how >> it has progressed. > > The difference here is that Mark's stuff wasn't as tightly integrated > with the kernel, IIRC. =A0What I saw was more at a user level - make = a big > file, map it, discard all the blocks, unlink the file. > > It was a good first step, but I think we can do a lot better by using > fs-specific calls to be efficient & targeted about the discards. > > Christoph has a similar approach for XFS, FWIW. > > -Eric I haven't looked closely at this patch, but I recall Mark consolidated numerous discontinuous trim/discard/unmap ranges into a single command to the SSD drive. That was why he felt he was getting superior performance. ie. There was an overhead per command to the drive that was eliminated if a single more complex command with multiple ranges went to the SSD drive. But he's the one that did the work and the benchmarking, so I'll let him take it from here, especially if I mis-understood what he was doing. Greg -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html