Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933102Ab1CWP0t (ORCPT ); Wed, 23 Mar 2011 11:26:49 -0400 Received: from mx1.fusionio.com ([64.244.102.30]:32938 "EHLO mx1.fusionio.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932773Ab1CWP0s (ORCPT ); Wed, 23 Mar 2011 11:26:48 -0400 X-ASG-Debug-ID: 1300894006-03d6a54f60c3bd0001-xx1T2L X-Barracuda-Envelope-From: JAxboe@fusionio.com Message-ID: <4D8A1133.20502@fusionio.com> Date: Wed, 23 Mar 2011 16:26:43 +0100 From: Jens Axboe MIME-Version: 1.0 To: Christoph Hellwig CC: "linux-kernel@vger.kernel.org" Subject: Re: merging discard request in the block layer References: <20110322194755.GA20122@infradead.org> <4D88FE5E.1010204@fusionio.com> <4D890EBD.1090103@fusionio.com> <20110323130137.GA10455@infradead.org> X-ASG-Orig-Subj: Re: merging discard request in the block layer In-Reply-To: <20110323130137.GA10455@infradead.org> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit X-Barracuda-Connect: mail1.int.fusionio.com[10.101.1.21] X-Barracuda-Start-Time: 1300894006 X-Barracuda-URL: http://10.101.1.180:8000/cgi-mod/mark.cgi X-Barracuda-Spam-Score: 0.00 X-Barracuda-Spam-Status: No, SCORE=0.00 using per-user scores of TAG_LEVEL=1000.0 QUARANTINE_LEVEL=1000.0 KILL_LEVEL=9.0 tests= X-Barracuda-Spam-Report: Code version 3.2, rules version 3.2.2.58745 Rule breakdown below pts rule name description ---- ---------------------- -------------------------------------------------- Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 923 Lines: 27 On 2011-03-23 14:01, Christoph Hellwig wrote: > On Tue, Mar 22, 2011 at 10:03:57PM +0100, Jens Axboe wrote: >>> That would seem to indicate a bug in the merging logic instead. >> >> What kind of max discard size does you device have? If the max discard >> size is smaller than the regular request size, this could help. > > It's a SCSI device, so the max discard size is a lot larger: > > # cat /sys/block/sda/queue/max_sectors_kb > 512 > # cat /sys/block/sda/queue/max_hw_sectors_kb > 32767 > # cat /sys/block/sda/queue/discard_max_bytes > 4294966784 I'll try and throw a synthetic test at it that produces a slew of discard merging and see what happens. -- Jens Axboe -- 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/