Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934771AbZDIPPr (ORCPT ); Thu, 9 Apr 2009 11:15:47 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S933910AbZDIPPQ (ORCPT ); Thu, 9 Apr 2009 11:15:16 -0400 Received: from one.firstfloor.org ([213.235.205.2]:34430 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934144AbZDIPPP (ORCPT ); Thu, 9 Apr 2009 11:15:15 -0400 To: Frederic Weisbecker Cc: LKML , Jeff Mahoney , Peter Zijlstra , ReiserFS Development List , Bron Gondwana , Andrew Morton , Linus Torvalds , Ingo Molnar , Alexander Viro Subject: Re: [PATCH] reiserfs: kill-the-BKL From: Andi Kleen References: <1239070789-13354-1-git-send-email-fweisbec@gmail.com> Date: Thu, 09 Apr 2009 17:15:09 +0200 In-Reply-To: <1239070789-13354-1-git-send-email-fweisbec@gmail.com> (Frederic Weisbecker's message of "Tue, 7 Apr 2009 04:19:49 +0200") Message-ID: <87tz4x97uq.fsf@basil.nowhere.org> User-Agent: Gnus/5.1008 (Gnus v5.10.8) Emacs/22.3 (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 Content-Length: 1142 Lines: 28 Frederic Weisbecker writes: > > So the new lock that replaces the bkl here is a per superblock mutex You have to be very careful with this. Mutexes can be slower than spinlocks (and the new BKL is a spinlock) in some situations, they typically schedule much more etc., which can be costly. So this might have actually made it slower if you're unlucky. There were some experimental changes recently to make mutexes more behave like spinlocks, but I don't think they're fully performance equivalent. Better would be to use spinlocks if possible. I guess you just would need to find all sleep points and wrap them with lock dropping? > After this patch, reiserfs suffers from a slight performance regression (for now). That might be related to the scheduling behaviour. Watch the reschedule counters in vmstat 1 -Andi -- ak@linux.intel.com -- Speaking for myself only. -- 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/