From: Jeff Moyer Subject: Re: [PATCH 1/2] fs: Do not dispatch FITRIM through separate super_operation Date: Thu, 18 Nov 2010 12:22:46 -0500 Message-ID: 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> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: 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 To: James Bottomley Return-path: Received: from mx1.redhat.com ([209.132.183.28]:31259 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932549Ab0KRR1T (ORCPT ); Thu, 18 Nov 2010 12:27:19 -0500 In-Reply-To: <1290100750.3041.72.camel@mulgrave.site> (James Bottomley's message of "Thu, 18 Nov 2010 11:19:10 -0600") Sender: linux-ext4-owner@vger.kernel.org List-ID: James Bottomley writes: > Not stepping into the debate: I'm happy to see punch go to the mapping > data and FITRIM pick it up later. > > However, I think it's time to question whether we actually still want to > allow online discard at all. Most of the benchmarks show it to be a net Define online discard, please. > lose to almost everything (either SSD or Thinly Provisioned arrays), so > it's become an "enable this to degrade performance" option with no > upside. Some SSDs very much require TRIMming to perform well as they age. If you're suggesting that we move from doing discards in journal commits to a batched discard, like the one Lukas implemented, then I think that's fine. If we need to reintroduce the finer-grained discards due to some hardware changes in the future, we can always do that. Cheers, Jeff