Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755199AbdGKG0n (ORCPT ); Tue, 11 Jul 2017 02:26:43 -0400 Received: from mx2.suse.de ([195.135.220.15]:57563 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751213AbdGKG0m (ORCPT ); Tue, 11 Jul 2017 02:26:42 -0400 Subject: Re: [RFC] mm/mremap: Remove redundant checks inside vma_expandable() To: Michal Hocko , Anshuman Khandual Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, mike.kravetz@oracle.com References: <20170710111059.30795-1-khandual@linux.vnet.ibm.com> <20170710134917.GB19645@dhcp22.suse.cz> <20170711060354.GA24852@dhcp22.suse.cz> From: Vlastimil Babka Message-ID: <4c182da0-6c84-df67-b173-6960fac0544a@suse.cz> Date: Tue, 11 Jul 2017 08:26:40 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0 MIME-Version: 1.0 In-Reply-To: <20170711060354.GA24852@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 719 Lines: 26 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?