From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f45.google.com (mail-pa0-f45.google.com [209.85.220.45]) by kanga.kvack.org (Postfix) with ESMTP id 36F436B0037 for ; Thu, 16 Jan 2014 11:27:02 -0500 (EST) Received: by mail-pa0-f45.google.com with SMTP id lf10so610369pab.18 for ; Thu, 16 Jan 2014 08:27:01 -0800 (PST) Received: from e23smtp06.au.ibm.com (e23smtp06.au.ibm.com. [202.81.31.148]) by mx.google.com with ESMTPS id xa2si7487309pab.345.2014.01.16.08.26.58 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Thu, 16 Jan 2014 08:27:00 -0800 (PST) Received: from /spool/local by e23smtp06.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 16 Jan 2014 21:16:08 +1000 Received: from d23relay03.au.ibm.com (d23relay03.au.ibm.com [9.190.235.21]) by d23dlp01.au.ibm.com (Postfix) with ESMTP id A34BF2CE8040 for ; Thu, 16 Jan 2014 22:16:04 +1100 (EST) Received: from d23av02.au.ibm.com (d23av02.au.ibm.com [9.190.235.138]) by d23relay03.au.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id s0GBFoi87012716 for ; Thu, 16 Jan 2014 22:15:51 +1100 Received: from d23av02.au.ibm.com (localhost [127.0.0.1]) by d23av02.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id s0GBG393022101 for ; Thu, 16 Jan 2014 22:16:03 +1100 Message-ID: <52D7C130.3010306@linux.vnet.ibm.com> Date: Thu, 16 Jan 2014 16:53:28 +0530 From: Raghavendra K T MIME-Version: 1.0 Subject: Re: [RFC PATCH V4] mm readahead: Fix readahead fail for no local memory and limit readahead pages References: <1389295490-28707-1-git-send-email-raghavendra.kt@linux.vnet.ibm.com> <20140110083656.GC26378@quack.suse.cz> <20140110095222.GE26378@quack.suse.cz> In-Reply-To: <20140110095222.GE26378@quack.suse.cz> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton , Linus Cc: Jan Kara , Fengguang Wu , David Cohen , Al Viro , Damien Ramonda , linux-mm@kvack.org, linux-kernel@vger.kernel.org On 01/10/2014 03:22 PM, Jan Kara wrote: > On Fri 10-01-14 09:36:56, Jan Kara wrote: >> On Fri 10-01-14 00:54:50, Raghavendra K T wrote: >>> We limit the number of readahead pages to 4k. >>> >>> max_sane_readahead returns zero on the cpu having no local memory >>> node. Fix that by returning a sanitized number of pages viz., >>> minimum of (requested pages, 4k, number of local free pages) >>> >>> Result: >>> fadvise experiment with FADV_WILLNEED on a x240 machine with 1GB testfile >>> 32GB* 4G RAM numa machine ( 12 iterations) yielded >>> >>> kernel Avg Stddev >>> base 7.264 0.56% >>> patched 7.285 1.14% >> OK, looks good to me. You can add: >> Reviewed-by: Jan Kara > Hum, while doing some other work I've realized there may be still a > problem hiding with the 16 MB limitation. E.g. the dynamic linker is > doing MADV_WILLNEED on the shared libraries. If the library (or executable) > is larger than 16 MB, then it may cause performance problems since access > is random in nature and we don't really know which part of the file do we > need first. > > I'm not sure what others think about this but I'm now more inclined to a > bit more careful and introduce the 16 MB limit only for the NUMA case. I.e. > something like: > Hi Linus, Andrew, Could you please let us know your suggestion or comment? -- 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