From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19]) by kanga.kvack.org (Postfix) with SMTP id 46AA16B004D for ; Sun, 16 Aug 2009 13:08:52 -0400 (EDT) Received: by ywh41 with SMTP id 41so3544282ywh.23 for ; Sun, 16 Aug 2009 10:08:54 -0700 (PDT) Message-ID: <4A883D21.5020209@gmail.com> Date: Sun, 16 Aug 2009 11:08:49 -0600 From: Robert Hancock MIME-Version: 1.0 Subject: Re: Discard support (was Re: [PATCH] swap: send callback when swap slot is freed) 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> <1250341176.4159.2.camel@mulgrave.site> <4A86B69C.7090001@rtr.ca> <1250344518.4159.4.camel@mulgrave.site> <4A86F2E1.8080002@hp.com> In-Reply-To: <4A86F2E1.8080002@hp.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: jim owens Cc: James Bottomley , Mark Lord , Chris Worley , Matthew Wilcox , 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 08/15/2009 11:39 AM, jim owens wrote: > ***begin rant*** > > I have not seen any analysis of the benefit and cost to the > end user of the TRIM or array UNMAP. We now see that TRIM > as implemented by some (all?) SSDs will come at high cost. > The cost is all born by the host. Do we get any benefit, or > is it all for the device vendor. And when we subtract the cost > from the benefit, does the user actually benefit and how? > > I'm tired of working around shit storage products and broken > device protocols from the "T" committees. I suggest we just > add a "white list" of devices that handle the discard fast > and without us needing NCQ queue drain. Then only send TRIM > to devices that are on the white list and throw the others > away in the block device layer. They all will require NCQ queue drain. It's an inherent requirement of the protocol that you can't overlap NCQ and non-NCQ commands, and the trim command is not NCQ. -- 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