From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757414AbcH3Gsl (ORCPT ); Tue, 30 Aug 2016 02:48:41 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:49291 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752175AbcH3Gsj (ORCPT ); Tue, 30 Aug 2016 02:48:39 -0400 X-IBM-Helo: d23dlp03.au.ibm.com X-IBM-MailFrom: khandual@linux.vnet.ibm.com X-IBM-RcptTo: linux-kernel@vger.kernel.org Date: Tue, 30 Aug 2016 12:17:07 +0530 From: Anshuman Khandual User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 To: Aaron Lu , Anshuman Khandual , Andrew Morton CC: Linux Memory Management List , "'Kirill A. Shutemov'" , Dave Hansen , Tim Chen , Huang Ying , Vlastimil Babka , Jerome Marchand , Andrea Arcangeli , Mel Gorman , Ebru Akagunduz , linux-kernel@vger.kernel.org Subject: Re: [PATCH] thp: reduce usage of huge zero page's atomic counter References: <20160829155021.2a85910c3d6b16a7f75ffccd@linux-foundation.org> <36b76a95-5025-ac64-0862-b98b2ebdeaf7@intel.com> <20160829203916.6a2b45845e8fb0c356cac17d@linux-foundation.org> <57C50F29.4070309@linux.vnet.ibm.com> <0342377a-26b8-16b9-5817-1964fac0e12d@intel.com> In-Reply-To: <0342377a-26b8-16b9-5817-1964fac0e12d@intel.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16083006-1617-0000-0000-000001509B1A X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 16083006-1618-0000-0000-0000469A3D66 Message-Id: <57C52BEB.8020104@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2016-08-30_03:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1604210000 definitions=main-1608300065 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/30/2016 11:24 AM, Aaron Lu wrote: > On 08/30/2016 12:44 PM, Anshuman Khandual wrote: >> > On 08/30/2016 09:09 AM, Andrew Morton wrote: >>> >> On Tue, 30 Aug 2016 11:09:15 +0800 Aaron Lu wrote: >>> >> >>>>>> >>>>> Case used for test on Haswell EP: >>>>>> >>>>> usemem -n 72 --readonly -j 0x200000 100G >>>>>> >>>>> Which spawns 72 processes and each will mmap 100G anonymous space and >>>>>> >>>>> then do read only access to that space sequentially with a step of 2MB. >>>>>> >>>>> >>>>>> >>>>> perf report for base commit: >>>>>> >>>>> 54.03% usemem [kernel.kallsyms] [k] get_huge_zero_page >>>>>> >>>>> perf report for this commit: >>>>>> >>>>> 0.11% usemem [kernel.kallsyms] [k] mm_get_huge_zero_page >>>>> >>>> >>>>> >>>> Does this mean that overall usemem runtime halved? >>>> >>> >>>> >>> Sorry for the confusion, the above line is extracted from perf report. >>>> >>> It shows the percent of CPU cycles executed in a specific function. >>>> >>> >>>> >>> The above two perf lines are used to show get_huge_zero_page doesn't >>>> >>> consume that much CPU cycles after applying the patch. >>>> >>> >>>>> >>>> >>>>> >>>> Do we have any numbers for something which is more real-wordly? >>>> >>> >>>> >>> Unfortunately, no real world numbers. >>>> >>> >>>> >>> We think the global atomic counter could be an issue for performance >>>> >>> so I'm trying to solve the problem. >>> >> >>> >> So, umm, we don't actually know if the patch is useful to anyone? >> > >> > On a POWER system it improves the CPU consumption of the above mentioned >> > function a little bit. Dont think its going to improve actual throughput >> > of the workload substantially. >> > >> > 0.07% usemem [kernel.vmlinux] [k] mm_get_huge_zero_page > I guess this is the base commit? But there shouldn't be the new > mm_get_huge_zero_page symbol before this patch. A typo perhaps? Yeah, sorry about that.