From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933495Ab3BLRNN (ORCPT ); Tue, 12 Feb 2013 12:13:13 -0500 Received: from mail-da0-f51.google.com ([209.85.210.51]:43751 "EHLO mail-da0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933372Ab3BLRNM (ORCPT ); Tue, 12 Feb 2013 12:13:12 -0500 Date: Tue, 12 Feb 2013 09:13:05 -0800 From: Tejun Heo To: Imre Deak Cc: Andrew Morton , linux-kernel@vger.kernel.org, Maxim Levitsky , Daniel Vetter , linaro-mm-sig@lists.linaro.org Subject: Re: [PATCH v2] lib/scatterlist: add simple page iterator Message-ID: <20130212171305.GB7348@htj.dyndns.org> References: <1353590706-1366-5-git-send-email-imre.deak@intel.com> <1360608604-3520-1-git-send-email-imre.deak@intel.com> <20130211125422.978c1e99.akpm@linux-foundation.org> <1360688840.5578.75.camel@localhost> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1360688840.5578.75.camel@localhost> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On Tue, Feb 12, 2013 at 07:07:20PM +0200, Imre Deak wrote: > It's the one implemented by sg_miter_{start,stop} in scatterlist.c. It > also iterates through a scatterlist a page at a time, but it also kmaps > these pages. Since in our use case we don't need to map the pages we > needed a solution without this overhead. I'm not against having non-mapping iterator but please consider that kmaps are no-ops on many configurations. It matters only for archs w/ high memory. > where each entry on the sglist contained 16 consecutive pages. This > takes ~10% more time for the uninlined version to run. This is a rather > artificial test and I couldn't come up with something more real-life > using only the i915 driver's ioctl interface that would show a > significant change in speed. > > So at least for now I'm ok with just uninlining all the helpers. Can we reimplement mapping iters using the new ones? Thanks. -- tejun