Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756686Ab2JZHDY (ORCPT ); Fri, 26 Oct 2012 03:03:24 -0400 Received: from mail-ob0-f174.google.com ([209.85.214.174]:58031 "EHLO mail-ob0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755522Ab2JZHDW (ORCPT ); Fri, 26 Oct 2012 03:03:22 -0400 Message-ID: <508A35B0.30106@gmail.com> Date: Fri, 26 Oct 2012 15:03:12 +0800 From: Ni zhan Chen User-Agent: Mozilla/5.0 (X11; Linux i686; rv:16.0) Gecko/20121011 Thunderbird/16.0.1 MIME-Version: 1.0 To: Fengguang Wu CC: Dave Chinner , YingHang Zhu , akpm@linux-foundation.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH] mm: readahead: remove redundant ra_pages in file_ra_state References: <20121024201921.GX4291@dastard> <20121025015014.GC29378@dastard> <50889FF1.9030107@gmail.com> <20121025025826.GB23462@localhost> <20121026002544.GI29378@dastard> <20121026012758.GA6282@localhost> <5089F5AD.5040708@gmail.com> <20121026065855.GA9179@localhost> In-Reply-To: <20121026065855.GA9179@localhost> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1211 Lines: 39 On 10/26/2012 02:58 PM, Fengguang Wu wrote: >> static void shrink_readahead_size_eio(struct file *filp, >> struct file_ra_state *ra) >> { >> - ra->ra_pages /= 4; >> + spin_lock(&filp->f_lock); >> + filp->f_mode |= FMODE_RANDOM; >> + spin_unlock(&filp->f_lock); >> >> As the example in comment above this function, the read maybe still >> sequential, and it will waste IO bandwith if modify to FMODE_RANDOM >> directly. > Yes immediately disabling readahead may hurt IO performance, the > original '/ 4' may perform better when there are only 1-3 IO errors > encountered. Hi Fengguang, Why the number should be 1-3? Regards, Chen > > Thanks, > Fengguang > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@kvack.org. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: email@kvack.org > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/