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 ESMTP id 76DA1600309 for ; Mon, 30 Nov 2009 13:59:16 -0500 (EST) Subject: Re: [PATCH] mm: don't discard unused swap slots by default From: "Martin K. Petersen" References: <20091030065102.GA2896@lst.de> <20091118171232.GB25541@lst.de> <20091130172243.GA30779@lst.de> Date: Mon, 30 Nov 2009 13:58:39 -0500 In-Reply-To: (Hugh Dickins's message of "Mon, 30 Nov 2009 18:28:41 +0000 (GMT)") Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-linux-mm@kvack.org To: Hugh Dickins Cc: Christoph Hellwig , Jens Axboe , Matthew Wilcox , linux-mm@kvack.org, linux-scsi@vger.kernel.org List-ID: >>>>> "Hugh" == Hugh Dickins writes: Hugh> You mentioned an "-o discard" mount option before: so I think what Hugh> we ought to be doing is an option to swapon. But you can imagine Hugh> that I'd prefer to avoid that too, if we can work this out without Hugh> it. The main problem we have is that the devices currently supporting TRIM are doing a piss poor job at it. We have pretty good vendor guarantees that discards are going to be essentially free on SCSI-class hardware. But in the ATA space things are currently being driven by early adopters / tweakers that care more about benchmarketing and feature checklists. Whether things actually work as intended is mostly irrelevant. I think we'll need to give things a little bit of time for decent ATA TRIM implementations to materialize. And then we can switch to an "assume it works, blacklist bad eggs" approach. Until then I think we need to make discard an explicit opt-in feature. -- Martin K. Petersen Oracle Linux Engineering -- 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