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 EB42C6B004D for ; Sun, 16 Aug 2009 12:32:55 -0400 (EDT) Message-ID: <4A8834B6.2070104@rtr.ca> Date: Sun, 16 Aug 2009 12:32:54 -0400 From: Mark Lord 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> <20090816150530.2bae6d1f@lxorguk.ukuu.org.uk> <20090816083434.2ce69859@infradead.org> <1250437927.3856.119.camel@mulgrave.site> In-Reply-To: <1250437927.3856.119.camel@mulgrave.site> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: James Bottomley Cc: Arjan van de Ven , Alan Cox , 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: James Bottomley wrote: > > For SSDs, the FTL has to have a separate operation: erase. Now, one > could see the correct implementation simply moving the sectors from the > in-use list to the to be cleaned list and still do the cleaning in the > background: that would be constant cost (but, again, likely expensive). > Of course, if SSD vendors decided to erase on the spot when seeing TRIM, > this wouldn't be true ... .. The SSDs based upon the Indilinx Barefoot controller appear to do the erase on the spot, along with a fair amount of garbage collection. The overhead does vary by size of the TRIM operation (number of sectors and extents), but even a single-sector TRIM has very high overhead. Samsung also now has SSDs at retail with TRIM. I don't have one of those here. -- 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