From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1163462AbWLGVxC (ORCPT ); Thu, 7 Dec 2006 16:53:02 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1163463AbWLGVxB (ORCPT ); Thu, 7 Dec 2006 16:53:01 -0500 Received: from mga03.intel.com ([143.182.124.21]:19667 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1163465AbWLGVxB (ORCPT ); Thu, 7 Dec 2006 16:53:01 -0500 X-ExtLoop1: 1 X-IronPort-AV: i="4.09,511,1157353200"; d="scan'208"; a="155331496:sNHT19499802" From: "Chen, Kenneth W" To: "'Nate Diller'" Cc: "Jens Axboe" , "linux-kernel" Subject: RE: [patch] speed up single bio_vec allocation Date: Thu, 7 Dec 2006 13:52:59 -0800 Message-ID: <000201c71a4a$0fa32280$ff0da8c0@amr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit X-Mailer: Microsoft Office Outlook 11 Thread-Index: AccaSSI4eoPBtsi+SuqmPbLUZsy62gAABi1g In-Reply-To: <5c49b0ed0612071346g5bccedd5q709e5ba66808c7fc@mail.gmail.com> X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Nate Diller wrote on Thursday, December 07, 2006 1:46 PM > the current code is straightforward and obviously correct. you want > to make the alloc/dealloc paths more complex, by special-casing for an > arbitrary limit of "small" I/O, AFAICT. of *course* you can expect > less overhead when you're doing one large I/O vs. two small ones, > that's the whole reason we have all this code to try to coalesce > contiguous I/O, do readahead, swap page clustering, etc. we *want* > more complexity if it will get us bigger I/Os. I don't see why we > want more complexity to reduce the *inherent* penalty of doing smaller > ones. You should check out the latest proposal from Jens Axboe which treats all biovec size the same and stuff it along with struct bio. I think it is a better approach than my first cut of special casing 1 segment biovec. His patch will speed up all sized I/O. - Ken