From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751621AbWDYVjE (ORCPT ); Tue, 25 Apr 2006 17:39:04 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751628AbWDYVjE (ORCPT ); Tue, 25 Apr 2006 17:39:04 -0400 Received: from pproxy.gmail.com ([64.233.166.176]:11699 "EHLO pproxy.gmail.com") by vger.kernel.org with ESMTP id S1751621AbWDYVjB (ORCPT ); Tue, 25 Apr 2006 17:39:01 -0400 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=beta; d=gmail.com; h=received:from:to:cc:subject:date:message-id:mime-version:content-type:content-transfer-encoding:x-mailer:in-reply-to:thread-index:x-mimeole; b=ijZ6SMO2T/mwaXTI2wt6OfcVIYVXL2Cz7QHF9Au2LXJYvQAPHjrLOxytuxpARKhvbKYyMJAxJI/lNN4Cttdpz1yDOyLL2m5MVEg18Ke8VSz8BuZATFhTeurt6LNT2OHnjG/pi5AHD6ZH7Ykvav9SwsC2INlYyOaJDFsntjHV3zo= From: "Hua Zhong" To: "'Jens Axboe'" Cc: , Subject: RE: [PATCH] likely cleanup: revert unlikely in ll_back_merge_fn Date: Tue, 25 Apr 2006 14:38:58 -0700 Message-ID: <004d01c668b0$a9c79540$853d010a@nuitysystems.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Mailer: Microsoft Office Outlook 11 In-Reply-To: <20060425183026.GR4102@suse.de> Thread-Index: AcZoljkoV+BecDHHQHWxqMKfjRq2iAAGb7ng X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2869 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org It seems that new BIOs do not have BIO_SEG_VALID set. So when you do sequential IO, the IO being back-merged should always have not had valid segments. I ran bonnie++ and it shows the same thing. > 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 >