Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752016Ab0KYElt (ORCPT ); Wed, 24 Nov 2010 23:41:49 -0500 Received: from mail-iw0-f174.google.com ([209.85.214.174]:62590 "EHLO mail-iw0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751659Ab0KYElr convert rfc822-to-8bit (ORCPT ); Wed, 24 Nov 2010 23:41:47 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc:content-type:content-transfer-encoding; b=o/j0PlO1ws5FFvvCxqGBtc6jAwbLxvstbJKOKY7OyWRUqhVBDytPRlQwaL9Z9M2lZB WDr4hzqeun4zCVzk437lK+gYlQwCQqVjxLlwcIygKG9L952e0VnPMNlJipFNS7cE2/Uq 6P+wn2UHTmGf+NSbqYbtbsjaVoF0Yt4uDQv0Q= MIME-Version: 1.0 In-Reply-To: <4CEDCE60.9050109@teksavvy.com> References: <20101118134804.GN5618@dhcp231-156.rdu.redhat.com> <20101118141957.GK6178@parisc-linux.org> <20101118142918.GA18510@infradead.org> <1290100750.3041.72.camel@mulgrave.site> <1290168976.2570.45.camel@dolmen> <4CE68155.50705@teksavvy.com> <20101119140203.GC10039@thunk.org> <4CE69940.6040908@teksavvy.com> <20101119163013.GJ10039@thunk.org> <4CEDCE60.9050109@teksavvy.com> From: Greg Freemyer Date: Wed, 24 Nov 2010 23:41:26 -0500 Message-ID: Subject: Re: [PATCH 1/2] fs: Do not dispatch FITRIM through separate super_operation To: Mark Lord Cc: "Ted Ts'o" , Lukas Czerner , Steven Whitehouse , James Bottomley , Christoph Hellwig , Matthew Wilcox , Josef Bacik , linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, sandeen@redhat.com Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2427 Lines: 64 On Wed, Nov 24, 2010 at 9:48 PM, Mark Lord wrote: > On 10-11-19 11:30 AM, Ted Ts'o wrote: >> >> On Fri, Nov 19, 2010 at 04:44:33PM +0100, Lukas Czerner wrote: >>>> >>>> But, oddly, it _is_ the default for mke2fs -t ext4, >>>> which really threw me for a loop recently. >>>> >>>> I though my system had locked up when suddenly everything >>>> went dead for a very long time (many minutes) while installing a >>>> new system. >> >> Yeah, the assumption was doing a single big discard (which is all >> mke2fs is doing) should be fast. ?At least on sanely implemented SSD's >> (i.e., like the Intel X25-M) it should be, since all that should >> require is a flash write to the global mapping table, declaring all of >> the blocks as free. > > But mke2fs probably is NOT doing a "single big discard", because for SATA > the > TRIM command is limited to 64K sectors per range.. and the in-kernel TRIM > code only ever does single ranges.. > > So doing a discard over an entire drive-encompassing partition, say.. 100GB, > will require 3000+ individual TRIM commands. ?At (say) 200msecs each, that > adds up to about ten minutes of execution time. ?Or less if the drive is > faster than that. > > Whereas.. grouping them into 64-ranges per trim, could reduce the execution > time down to perhaps 1/50th of that, or in the range of 10-20 seconds > instead. > > Cheers Mark, With recent kernels, this is supposed to work as you describe. ie. 64 contiguous ranges per trim command. If you see a significant speed difference between mke2fs and running wiper.sh on that same filesystem immediately after formatting, then their is likely a bug worth chasing. Are you seeing an actual speed difference, or just assuming there is one? If mke2fs is slower than wiper.sh, what kernel are you testing with? Greg -- Greg Freemyer Head of EDD Tape Extraction and Processing team Litigation Triage Solutions Specialist http://www.linkedin.com/in/gregfreemyer CNN/TruTV Aired Forensic Imaging Demo - ?? http://insession.blogs.cnn.com/2010/03/23/how-computer-evidence-gets-retrieved/ The Norcross Group The Intersection of Evidence & Technology http://www.norcrossgroup.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/