From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f175.google.com (mail-wi0-f175.google.com [209.85.212.175]) by kanga.kvack.org (Postfix) with ESMTP id 3CEA56B0031 for ; Tue, 18 Feb 2014 07:04:36 -0500 (EST) Received: by mail-wi0-f175.google.com with SMTP id hm4so3399558wib.2 for ; Tue, 18 Feb 2014 04:04:35 -0800 (PST) Received: from mx2.suse.de (cantor2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id k1si14298951wjz.126.2014.02.18.04.04.34 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Tue, 18 Feb 2014 04:04:34 -0800 (PST) Date: Tue, 18 Feb 2014 13:04:30 +0100 From: Jan Kara Subject: Re: [PATCH V6 ] mm readahead: Fix readahead fail for memoryless cpu and limit readahead pages Message-ID: <20140218120430.GC29660@quack.suse.cz> References: <1392708338-19685-1-git-send-email-raghavendra.kt@linux.vnet.ibm.com> <20140218094920.GB29660@quack.suse.cz> <53034C66.90707@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <53034C66.90707@linux.vnet.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: 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 On Tue 18-02-14 17:34:54, Raghavendra K T wrote: > 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. Good. You can add my: Acked-by: Jan Kara > ( some time it is even faster.. may be because we do not do free > page calculation?. ) Hardly, that calculation is just a tiny amount of CPU time in the startup of the application. If there is really a significant difference, it might be because we don't preload stuff which isn't used in the end. Honza -- Jan Kara SUSE Labs, CR -- 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