From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wj0-f198.google.com (mail-wj0-f198.google.com [209.85.210.198]) by kanga.kvack.org (Postfix) with ESMTP id AB6D46B0033 for ; Wed, 18 Jan 2017 04:50:28 -0500 (EST) Received: by mail-wj0-f198.google.com with SMTP id an2so1476013wjc.3 for ; Wed, 18 Jan 2017 01:50:28 -0800 (PST) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id n107si28470800wrb.302.2017.01.18.01.50.27 for (version=TLS1 cipher=AES128-SHA bits=128/128); Wed, 18 Jan 2017 01:50:27 -0800 (PST) Subject: Re: [RFC 3/4] mm, page_alloc: move cpuset seqcount checking to slowpath References: <20170117221610.22505-1-vbabka@suse.cz> <20170117221610.22505-4-vbabka@suse.cz> <20170118094054.GJ7015@dhcp22.suse.cz> From: Vlastimil Babka Message-ID: <7b984dde-78c5-2efc-daef-bcdcc51fc9cb@suse.cz> Date: Wed, 18 Jan 2017 10:48:55 +0100 MIME-Version: 1.0 In-Reply-To: <20170118094054.GJ7015@dhcp22.suse.cz> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Mel Gorman , Ganapatrao Kulkarni , linux-kernel@vger.kernel.org, linux-mm@kvack.org On 01/18/2017 10:40 AM, Michal Hocko wrote: > On Tue 17-01-17 23:16:09, Vlastimil Babka wrote: >> This is a preparation for the following patch to make review simpler. While >> the primary motivation is a bug fix, this could also save some cycles in the >> fast path. > > I cannot say I would be happy about this patch :/ The code is still very > confusing and subtle. I really think we should get rid of > synchronization with the concurrent cpuset/mempolicy updates instead. > Have you considered that instead? Not so thoroughly yet, but I already suspect it would be intrusive for stable. We could make copies of nodemask and mems_allowed and protect just the copying with seqcount, but that would mean overhead and stack space. Also we might try revert 682a3385e773 ("mm, page_alloc: inline the fast path of the zonelist iterator") ... -- 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