From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757189Ab2DIONx (ORCPT ); Mon, 9 Apr 2012 10:13:53 -0400 Received: from mx1.redhat.com ([209.132.183.28]:29203 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757044Ab2DIONV (ORCPT ); Mon, 9 Apr 2012 10:13:21 -0400 From: Jeff Moyer To: Jens Axboe Cc: Shaohua Li , "linux-kernel\@vger.kernel.org" Subject: Re: [PATCH]block: make auto block plug flush threshold per-disk based References: <4F7F2765.3090003@kernel.org> <4F7F2A3D.3010700@kernel.dk> X-PGP-KeyID: 1F78E1B4 X-PGP-CertKey: F6FE 280D 8293 F72C 65FD 5A58 1FF8 A7CA 1F78 E1B4 X-PCLoadLetter: What the f**k does that mean? Date: Mon, 09 Apr 2012 10:13:12 -0400 In-Reply-To: <4F7F2A3D.3010700@kernel.dk> (Jens Axboe's message of "Fri, 06 Apr 2012 11:39:09 -0600") Message-ID: User-Agent: Gnus/5.110011 (No Gnus v0.11) Emacs/23.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Jens Axboe writes: > On 2012-04-06 11:27, Shaohua Li wrote: >> We do auto block plug flush to reduce latency, the threshold is 16 >> requests. This works well if the task is accessing one or two drives. >> The problem is if the task is accessing a raid 0 device and the raid >> disk number is big, say 8 or 16, 16/8 = 2 or 16/16=1, we will have >> heavy lock contention. >> >> This patch makes the threshold per-disk based. The latency should be >> still ok accessing one or two drives. The setup with application >> accessing a lot of drives in the meantime uaually is big machine, >> avoiding lock contention is more important, because any contention >> will actually increase latency. > > Thanks, applied. It should have been per-queue all along, so this > makes a lot of sense. Yeah, I had noticed this before when looking over the code. Makes sense. Acked-by: Jeff Moyer