From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f72.google.com (mail-pg0-f72.google.com [74.125.83.72]) by kanga.kvack.org (Postfix) with ESMTP id 6A3A76B04E5 for ; Tue, 11 Jul 2017 07:09:10 -0400 (EDT) Received: by mail-pg0-f72.google.com with SMTP id p15so145727753pgs.7 for ; Tue, 11 Jul 2017 04:09:10 -0700 (PDT) Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com. [148.163.156.1]) by mx.google.com with ESMTPS id q85si4705039pfa.458.2017.07.11.04.09.09 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 11 Jul 2017 04:09:09 -0700 (PDT) Received: from pps.filterd (m0098409.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.21/8.16.0.21) with SMTP id v6BB95JR107094 for ; Tue, 11 Jul 2017 07:09:08 -0400 Received: from e23smtp04.au.ibm.com (e23smtp04.au.ibm.com [202.81.31.146]) by mx0a-001b2d01.pphosted.com with ESMTP id 2bmb3f5ray-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Tue, 11 Jul 2017 07:09:08 -0400 Received: from localhost by e23smtp04.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 11 Jul 2017 21:08:51 +1000 Received: from d23av01.au.ibm.com (d23av01.au.ibm.com [9.190.234.96]) by d23relay08.au.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id v6BB8ne523658580 for ; Tue, 11 Jul 2017 21:08:49 +1000 Received: from d23av01.au.ibm.com (localhost [127.0.0.1]) by d23av01.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id v6BB8mc6009889 for ; Tue, 11 Jul 2017 21:08:48 +1000 Subject: Re: [RFC] mm/mremap: Remove redundant checks inside vma_expandable() 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> <337a8a4c-1f27-7371-409d-6a9f181b3871@suse.cz> From: Anshuman Khandual Date: Tue, 11 Jul 2017 16:38:46 +0530 MIME-Version: 1.0 In-Reply-To: <337a8a4c-1f27-7371-409d-6a9f181b3871@suse.cz> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Message-Id: <8bcc5908-7f0d-ba5c-a484-e0763f9b7664@linux.vnet.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: Vlastimil Babka , Michal Hocko Cc: Anshuman Khandual , linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, mike.kravetz@oracle.com On 07/11/2017 12:26 PM, Vlastimil Babka wrote: > On 07/11/2017 08:50 AM, Michal Hocko wrote: >> On Tue 11-07-17 08:26:40, Vlastimil Babka wrote: >>> On 07/11/2017 08:03 AM, Michal Hocko wrote: >>>> >>>> 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? > > I think it is: "Checking for availability of virtual address range at > the end of the VMA for the incremental size is also reduntant at this > point." > >> The >> changelog is silent about it. > > It doesn't explain why it's redundant, indeed. Unfortunately, the commit > f106af4e90ea ("fix checks for expand-in-place mremap") which added this, > also doesn't explain why it's needed. Its redundant because there are calls to get_unmapped_area() down the line in the function whose failure will anyway fail the expansion of the VMA. -- 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