Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752442Ab0KSDmc (ORCPT ); Thu, 18 Nov 2010 22:42:32 -0500 Received: from ironport2-out.teksavvy.com ([206.248.154.183]:35819 "EHLO ironport2-out.pppoe.ca" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751209Ab0KSDmb (ORCPT ); Thu, 18 Nov 2010 22:42:31 -0500 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: ApIBACOA5UxLd/sX/2dsb2JhbAAHgz3MYJECgSKDNnMEhFqLEA X-IronPort-AV: E=Sophos;i="4.59,221,1288584000"; d="scan'208";a="82945886" Message-ID: <4CE5F21F.7010806@teksavvy.com> Date: Thu, 18 Nov 2010 22:42:23 -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: "Martin K. Petersen" CC: Greg Freemyer , James Bottomley , 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> <4CE5C616.7070706@teksavvy.com> In-Reply-To: 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: 1627 Lines: 36 On 10-11-18 08:49 PM, Martin K. Petersen wrote: > So assuming we walk the filesystem to reclaim space on ATA SSDs on a > weekly basis (since that's the only sane approach): > > What is the performance impact of not coalescing discontiguous > block ranges when cron scrubs your /home at 4am Sunday morning? In the case of FITRIM, you're right: the performance impact probably doesn't matter much for a 4am cronjob. But a lot of people currently (at least) prefer to run it manually, and they don't want it to take forever. Though that's still not the primary worry: each TRIM seems to trigger a flash erase cycle (or cycles) on the most common SSDs on the market, including anything Indilinx-based and as far as I can tell also for anything SandForce based. That's probably 70% of the SSDs out there today. And I'm very concerned about premature wear -- MLC is only for 10000 cycles (avg). Also, the current one-range-at-a-time interface is just not correct for the majority of devices out there: they are SATA, not some obscure enterprise-only one-range-at-a-time thing. We need an implementation that reflects real-life for uses other than data centres. If nobody else does it, I'll probably implement it correctly this winter. But it would really be better for a real filesystem/DM person to do it. Thanks for hanging in there this far, though! 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/