From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx161.postini.com [74.125.245.161]) by kanga.kvack.org (Postfix) with SMTP id 3E86B6B004D for ; Tue, 24 Jan 2012 20:45:36 -0500 (EST) Message-ID: <4F1F5EB8.3000407@fb.com> Date: Tue, 24 Jan 2012 17:45:28 -0800 From: Arun Sharma MIME-Version: 1.0 Subject: Re: [PATCH] mm: Enable MAP_UNINITIALIZED for archs with mmu References: <1326912662-18805-1-git-send-email-asharma@fb.com> <20120119114206.653b88bd.kamezawa.hiroyu@jp.fujitsu.com> <4F1E013E.9060009@fb.com> <20120124120704.3f09b206.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20120124120704.3f09b206.kamezawa.hiroyu@jp.fujitsu.com> Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: KAMEZAWA Hiroyuki Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Balbir Singh , akpm@linux-foundation.org On 1/23/12 7:07 PM, KAMEZAWA Hiroyuki wrote: > You can see reduction of clear_page() cost by removing GFP_ZERO but > what's your application's total performance ? Is it good enough considering > many risks ? I see 90k calls/sec to clear_page_c when running our application. I don't have data on the impact of GFP_ZERO alone, but an earlier experiment when we tuned malloc to not call madvise(MADV_DONTNEED) aggressively saved us 3% CPU. So I'm expecting this to be a 1-2% win. But not calling madvise() increases our RSS and increases the risk of OOM. Agree with your analysis that removing the cache misses at clear_page() is not always a win, since it moves the misses to the code where the app first touches the data. -Arun -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755529Ab2AYBpl (ORCPT ); Tue, 24 Jan 2012 20:45:41 -0500 Received: from mx0a-00082601.pphosted.com ([67.231.145.42]:58352 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754694Ab2AYBpk (ORCPT ); Tue, 24 Jan 2012 20:45:40 -0500 Message-ID: <4F1F5EB8.3000407@fb.com> Date: Tue, 24 Jan 2012 17:45:28 -0800 From: Arun Sharma User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.7; rv:8.0) Gecko/20111105 Thunderbird/8.0 MIME-Version: 1.0 To: KAMEZAWA Hiroyuki CC: , , Balbir Singh , Subject: Re: [PATCH] mm: Enable MAP_UNINITIALIZED for archs with mmu References: <1326912662-18805-1-git-send-email-asharma@fb.com> <20120119114206.653b88bd.kamezawa.hiroyu@jp.fujitsu.com> <4F1E013E.9060009@fb.com> <20120124120704.3f09b206.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20120124120704.3f09b206.kamezawa.hiroyu@jp.fujitsu.com> Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [192.168.18.252] X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:5.6.7361,1.0.211,0.0.0000 definitions=2012-01-25_01:2012-01-24,2012-01-25,1970-01-01 signatures=0 X-Proofpoint-Spam-Reason: safe Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 1/23/12 7:07 PM, KAMEZAWA Hiroyuki wrote: > You can see reduction of clear_page() cost by removing GFP_ZERO but > what's your application's total performance ? Is it good enough considering > many risks ? I see 90k calls/sec to clear_page_c when running our application. I don't have data on the impact of GFP_ZERO alone, but an earlier experiment when we tuned malloc to not call madvise(MADV_DONTNEED) aggressively saved us 3% CPU. So I'm expecting this to be a 1-2% win. But not calling madvise() increases our RSS and increases the risk of OOM. Agree with your analysis that removing the cache misses at clear_page() is not always a win, since it moves the misses to the code where the app first touches the data. -Arun