From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758951Ab2C2Agm (ORCPT ); Wed, 28 Mar 2012 20:36:42 -0400 Received: from oproxy4-pub.bluehost.com ([69.89.21.11]:44033 "HELO oproxy4-pub.bluehost.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1757930Ab2C2Agj (ORCPT ); Wed, 28 Mar 2012 20:36:39 -0400 Message-ID: <4F73AE95.1060402@tao.ma> Date: Thu, 29 Mar 2012 08:36:37 +0800 From: Tao Ma User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.28) Gecko/20120313 Thunderbird/3.1.20 MIME-Version: 1.0 To: Greg KH CC: linux-kernel@vger.kernel.org, Jens Axboe Subject: Re: [PATCH] block: Make cfq_target_latency tunable through sysfs. References: <1332836213-5266-1-git-send-email-tm@tao.ma> <20120329003228.GA18424@kroah.com> In-Reply-To: <20120329003228.GA18424@kroah.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Identified-User: {1390:box585.bluehost.com:colyli:tao.ma} {sentby:smtp auth 69.198.183.141 authed with tm@tao.ma} Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/29/2012 08:32 AM, Greg KH wrote: > On Tue, Mar 27, 2012 at 04:16:53PM +0800, Tao Ma wrote: >> From: Tao Ma >> >> In cfq, when we calculate a time slice for a process(or a cfqq to >> be precise), we have to consider the cfq_target_latency so that all the >> sync request have an estimated latency(300ms) and it is controlled by >> cfq_target_latency. But in some hadoop test, we have found that if >> there are many processes doing sequential read(24 for example), the >> throughput is bad because every process can only work for about 25ms >> and the cfqq is switched. That leads to a higher disk seek. We can >> achive the good throughput by setting low_latency=0, but then some >> read's latency is too much for the application. >> >> So this patch makes cfq_target_latency tunable through sysfs so that >> we can tune it and find some magic number which is not bad for both >> the throughput and the read latency. > > If you add/modify sysfs files, you HAVE to also have a matching change > to Documentation/ABI. OK, I will add it in the next round. Great thanks. Tao > > Please do so. > > thanks, > > greg k-h > -- > 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/