From: =?utf-8?B?SsO2cm4=?= Engel Subject: Re: Is TRIM/DISCARD going to be a performance problem? Date: Mon, 11 May 2009 12:06:24 +0200 Message-ID: <20090511100624.GB6585@logfs.org> References: <20090510165259.GA31850@logfs.org> <20090511083754.GA29082@mit.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Matthew Wilcox , Jens Axboe , Ric Wheeler , linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org To: Theodore Tso Return-path: Received: from lazybastard.de ([212.112.238.170]:33598 "EHLO longford.logfs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755632AbZEKKGn convert rfc822-to-8bit (ORCPT ); Mon, 11 May 2009 06:06:43 -0400 Content-Disposition: inline In-Reply-To: <20090511083754.GA29082@mit.edu> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Mon, 11 May 2009 04:37:54 -0400, Theodore Tso wrote: >=20 > Well, no one has actually implemented the low-level TRIM support yet; Iirc dwmw2 did so for some of the FTL drivers. More a curiosity than a useful device, though. > Well, no, Matthew's changes didn't do any of that, I suspect because > most SSD's, including X25-M, are expected to have a granularity size > of 1 block. It's the crazy people in the SCSI standards world who've > been pushing for granlarity sizes in the 1-4 megabyte range; as I > understand things, the granularity issue was not going to be a proble= m > for the ATA TRIM command. I am not sure about this part. So far Intel has been the only party to release any information about their dark-grey box. All other boxes are still solid black. And until I'm told otherwise I'd consider them to b= e stupid devices that use erase block size as trim granularity. Given the total lack of information, your guess is as good as mine, though. > As far as thinking that the proposal is ludicrous --- what precisely > did you find ludicrous about it? Mainly the idea that discard requests should act as barriers and instea= d of fixing that, you propose a lot of complexity to work around it. > The only problem with SSD's is the people who designed the ATA TRIM > command requires us to completely drian the I/O queue before issuing > it. Because of this incompetence, we need to be a bit more careful > about how we issue them. And this bit that I wasn't aware of. Such a requirement in the standar= d is a trainwreck indeed. J=C3=B6rn --=20 Victory in war is not repetitious. -- Sun Tzu -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html