Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760746Ab0KRWHH (ORCPT ); Thu, 18 Nov 2010 17:07:07 -0500 Received: from ironport2-out.teksavvy.com ([206.248.154.181]:38304 "EHLO ironport2-out.pppoe.ca" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754952Ab0KRWHE (ORCPT ); Thu, 18 Nov 2010 17:07:04 -0500 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: ApIBAJ4x5UxLd/sX/2dsb2JhbAAHgz3ONpBygSKDNnMEhFqLEA X-IronPort-AV: E=Sophos;i="4.59,219,1288584000"; d="scan'208";a="82910916" Message-ID: <4CE5A386.7000105@teksavvy.com> Date: Thu, 18 Nov 2010 17:07:02 -0500 From: Mark Lord User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-GB; rv:1.9.2.12) Gecko/20101027 Thunderbird/3.1.6 MIME-Version: 1.0 To: James Bottomley CC: Greg Freemyer , Jeff Moyer , Christoph Hellwig , Matthew Wilcox , Josef Bacik , Lukas Czerner , tytso@mit.edu, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, sandeen@redhat.com Subject: Re: [PATCH 1/2] fs: Do not dispatch FITRIM through separate super_operation References: <1290065809-3976-1-git-send-email-lczerner@redhat.com> <20101118130630.GJ6178@parisc-linux.org> <20101118134804.GN5618@dhcp231-156.rdu.redhat.com> <20101118141957.GK6178@parisc-linux.org> <20101118142918.GA18510@infradead.org> <1290100750.3041.72.camel@mulgrave.site> <1290102098.3041.77.camel@mulgrave.site> <4CE59E57.2090009@teksavvy.com> <1290117009.11007.42.camel@mulgrave.site> In-Reply-To: <1290117009.11007.42.camel@mulgrave.site> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 960 Lines: 23 On 10-11-18 04:50 PM, James Bottomley wrote: > > Before we go gung ho on this, there's no evidence that N discontiguous > ranges in one command are any better than the ranges sent N times ... > the same amount of erase overhead gets sent on SSDs. No, we do have evidence: execution time of the TRIM commands on the SSD. The one-range-at-a-time is incredibly slow compared to multiple ranges at a time. That slowness comes from somewhere, with about 99.9% certainty that it is due to the drive performing slow flash erase cycles. I think perhaps we should do the batching as much as possible, and then split them into single ranges for LLDs that cannot handle multi-ranges. Way more efficient that way. Cheers -- 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/