From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755268AbaHUVoS (ORCPT ); Thu, 21 Aug 2014 17:44:18 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:54624 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755172AbaHUVoO (ORCPT ); Thu, 21 Aug 2014 17:44:14 -0400 Date: Thu, 21 Aug 2014 14:44:12 -0700 From: Andrew Morton To: Akinobu Mita Cc: LKML , Jens Axboe , Alexander Viro , Jeff Moyer , linux-fsdevel@vger.kernel.org Subject: Re: [PATCH 0/3] implement readpages() for block device to optimize sequential read Message-Id: <20140821144412.2a97f2a7400590097f3926de@linux-foundation.org> In-Reply-To: References: <1407249514-20465-1-git-send-email-akinobu.mita@gmail.com> <20140814150425.dfbb6c7eb7ab250e985dac28@linux-foundation.org> X-Mailer: Sylpheed 3.2.0beta5 (GTK+ 2.24.10; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 16 Aug 2014 02:09:44 +0900 Akinobu Mita wrote: > 2014-08-15 7:04 GMT+09:00 Andrew Morton : > > On Tue, 5 Aug 2014 23:38:31 +0900 Akinobu Mita wrote: > > > >> This patchset implements readpages() operation for block device by > >> using mpage_readpages() which can create multipage BIOs instead of > >> BIOs for each page and reduce system CPU time consumption. > > > > Patchset is simple and straightforward enough. But who the > > heck cares about the performance of buffered reads from /dev/XXX? > > I tend to consider the block device as a baseline when I measure the > performance of the storage device. So I was a bit surprised when I saw > the performance of buffered reads from filesystem is better than the one > from block device. That is the reason about this patch for me. OK. The lack of readpages for blockdevs has been an outstanding oddity for a decade or longer - I think it's just that nobody was motivated to do it because the workload isn't important. But the implementation looks pretty simple so why not clean it up. I grabbed the patches.