Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755311AbdGKLHC (ORCPT ); Tue, 11 Jul 2017 07:07:02 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:36159 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754141AbdGKLHA (ORCPT ); Tue, 11 Jul 2017 07:07:00 -0400 Subject: Re: [RFC] mm/mremap: Remove redundant checks inside vma_expandable() To: Michal Hocko , Vlastimil Babka References: <20170710111059.30795-1-khandual@linux.vnet.ibm.com> <20170710134917.GB19645@dhcp22.suse.cz> <20170711060354.GA24852@dhcp22.suse.cz> <4c182da0-6c84-df67-b173-6960fac0544a@suse.cz> <20170711065030.GE24852@dhcp22.suse.cz> Cc: Anshuman Khandual , linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, mike.kravetz@oracle.com From: Anshuman Khandual Date: Tue, 11 Jul 2017 16:36:40 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.5.1 MIME-Version: 1.0 In-Reply-To: <20170711065030.GE24852@dhcp22.suse.cz> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable x-cbid: 17071111-0008-0000-0000-0000014F9B58 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17071111-0009-0000-0000-000009800D5C Message-Id: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-07-11_05:,, 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=8.0.1-1703280000 definitions=main-1707110175 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 977 Lines: 29 On 07/11/2017 12:20 PM, Michal Hocko wrote: > On Tue 11-07-17 08:26:40, Vlastimil Babka wrote: >> On 07/11/2017 08:03 AM, Michal Hocko wrote: >>> On Tue 11-07-17 09:58:42, Anshuman Khandual wrote: >>>>> here. This is hardly something that would save many cycles in a >>>>> relatively cold path. >>>> Though I have not done any detailed instruction level measurement, >>>> there is a reduction in real and system amount of time to execute >>>> the test with and without the patch. >>>> >>>> Without the patch >>>> >>>> real 0m2.100s >>>> user 0m0.162s >>>> sys 0m1.937s >>>> >>>> With this patch >>>> >>>> real 0m0.928s >>>> user 0m0.161s >>>> sys 0m0.756s >>> Are you telling me that two if conditions cause more than a second >>> difference? That sounds suspicious. >> It's removing also a call to get_unmapped_area(), AFAICS. That means a >> vma search? > Ohh, right. I have somehow missed that. Is this removal intentional? The > changelog is silent about it. Yeah it was.