From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932281AbWDYS3v (ORCPT ); Tue, 25 Apr 2006 14:29:51 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932286AbWDYS3v (ORCPT ); Tue, 25 Apr 2006 14:29:51 -0400 Received: from ns.virtualhost.dk ([195.184.98.160]:15708 "EHLO virtualhost.dk") by vger.kernel.org with ESMTP id S932281AbWDYS3u (ORCPT ); Tue, 25 Apr 2006 14:29:50 -0400 Date: Tue, 25 Apr 2006 20:30:26 +0200 From: Jens Axboe To: Hua Zhong Cc: linux-kernel@vger.kernel.org, akpm@osdl.org Subject: Re: [PATCH] likely cleanup: revert unlikely in ll_back_merge_fn Message-ID: <20060425183026.GR4102@suse.de> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 25 2006, Hua Zhong wrote: > With likely/unlikely profiling (see the recent patch dwalker@mvista.com > sent), on my not-so-busy-typical-development system it shows more than > 80K misses and no hits. So I guess it makes sense to revert. > > I don't know BIO code very well, but I hope this data is useful for the > experts. Well you'd want to optimize for the busy case, right, no point in optimizing for a more idle system. I'm not at all uninterested in this, I'd just like to see a more intelligent/controlled work load that actually stresses the io subsystem being profiled. If you have a not-so-busy system, you like don't do enough IO to trigger a lot of merges. Or maybe you do, and we just have a bug somewhere so that we unfortunately repeatedly recount segments. Care to run a simple io benchmark and profile that? -- Jens Axboe