From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932298AbaCQCIG (ORCPT ); Sun, 16 Mar 2014 22:08:06 -0400 Received: from mx1.redhat.com ([209.132.183.28]:42910 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932129AbaCQCHr (ORCPT ); Sun, 16 Mar 2014 22:07:47 -0400 References: <1392708338-19685-1-git-send-email-raghavendra.kt@linux.vnet.ibm.com> <20140218094920.GB29660@quack.suse.cz> <53034C66.90707@linux.vnet.ibm.com> User-agent: mu4e 0.9.9.6pre2; emacs 24.3.1 From: Madper Xie To: Raghavendra K T Cc: Jan Kara , Andrew Morton , Fengguang Wu , David Cohen , Al Viro , Damien Ramonda , rientjes@google.com, Linus , nacc@linux.vnet.ibm.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH V6 ] mm readahead: Fix readahead fail for memoryless cpu and limit readahead pages In-reply-to: <53034C66.90707@linux.vnet.ibm.com> Date: Mon, 17 Mar 2014 10:07:23 +0800 Message-ID: <871ty1zig4.fsf@redhat.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Raghavendra K T writes: > On 02/18/2014 03:19 PM, Jan Kara wrote: >> On Tue 18-02-14 12:55:38, Raghavendra K T wrote: >>> Currently max_sane_readahead() returns zero on the cpu having no local memory node >>> which leads to readahead failure. Fix the readahead failure by returning >>> minimum of (requested pages, 512). Users running application on a memory-less cpu >>> which needs readahead such as streaming application see considerable boost in the >>> performance. >>> >>> Result: >>> fadvise experiment with FADV_WILLNEED on a PPC machine having memoryless CPU >>> with 1GB testfile ( 12 iterations) yielded around 46.66% improvement. >>> >>> fadvise experiment with FADV_WILLNEED on a x240 machine with 1GB testfile >>> 32GB* 4G RAM numa machine ( 12 iterations) showed no impact on the normal >>> NUMA cases w/ patch. >> Can you try one more thing please? Compare startup time of some big >> executable (Firefox or LibreOffice come to my mind) for the patched and >> normal kernel on a machine which wasn't hit by this NUMA issue. And don't >> forget to do "echo 3 >/proc/sys/vm/drop_caches" before each test to flush >> the caches. If this doesn't show significant differences, I'm OK with the >> patch. >> > > Thanks Honza, I checked with firefox (starting to particular point).. > I do not see any difference. Both the case took around 14sec. > > ( some time it is even faster.. may be because we do not do free page > calculation?. ) Hi. Just a concern. Will the performance reduce on some special storage backend? E.g. tape. The existent applications may using readahead for userspace I/O schedule to decrease seeking time. -- Thanks, Madper