From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with SMTP id 3FDA86B004F for ; Fri, 14 Aug 2009 20:19:34 -0400 (EDT) Received: by yxe14 with SMTP id 14so2409509yxe.12 for ; Fri, 14 Aug 2009 17:19:39 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20090814234539.GE27148@parisc-linux.org> References: <200908122007.43522.ngupta@vflare.org> <20090813151312.GA13559@linux.intel.com> <20090813162621.GB1915@phenom2.trippelsdorf.de> <87f94c370908131115r680a7523w3cdbc78b9e82373c@mail.gmail.com> <3e8340490908131354q167840fcv124ec56c92bbb830@mail.gmail.com> <4A85E0DC.9040101@rtr.ca> <20090814234539.GE27148@parisc-linux.org> Date: Fri, 14 Aug 2009 18:19:39 -0600 Message-ID: Subject: Re: Discard support (was Re: [PATCH] swap: send callback when swap slot is freed) From: Chris Worley Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org To: Matthew Wilcox Cc: Mark Lord , Bryan Donlan , david@lang.hm, Greg Freemyer , Markus Trippelsdorf , Matthew Wilcox , Hugh Dickins , Nitin Gupta , Ingo Molnar , Peter Zijlstra , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-scsi@vger.kernel.org, linux-ide@vger.kernel.org, Linux RAID List-ID: On Fri, Aug 14, 2009 at 5:45 PM, Matthew Wilcox wrote: > On Fri, Aug 14, 2009 at 05:21:32PM -0600, Chris Worley wrote: >> Sooner is better than waiting to coalesce. =A0The longer an LBA is >> inactive, the better for any management scheme. =A0If you wait until >> it's reused, you might as well forgo the advantages of TRIM/UNMAP. =A0If >> a the controller wants to coalesce, let it coalesce. > > I'm sorry, you're wrong. =A0There is a tradeoff point, and it's different > for each drive model. =A0Sending down a steady stream of tiny TRIMs is > going to give terrible performance. Sounds like you might be using junk for a device? For junk, a little coalescing may be warranted... like in the I/O schedular, but no more than 100usecs wait before posting, or then you effect high performing devices too. Chris > > -- > Matthew Wilcox =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0Intel O= pen Source Technology Centre > "Bill, look, we understand that you're interested in selling us this > operating system, but compare it to ours. =A0We can't possibly take such > a retrograde step." > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org