From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751757AbaJTPom (ORCPT ); Mon, 20 Oct 2014 11:44:42 -0400 Received: from mx1.redhat.com ([209.132.183.28]:16419 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750716AbaJTPol (ORCPT ); Mon, 20 Oct 2014 11:44:41 -0400 Message-ID: <54452DD2.8090205@redhat.com> Date: Mon, 20 Oct 2014 11:44:18 -0400 From: Rik van Riel User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.7.0 MIME-Version: 1.0 To: Vlastimil Babka , Andrew Morton CC: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Minchan Kim , Mel Gorman , Joonsoo Kim , Michal Nazarewicz , Naoya Horiguchi , Christoph Lameter , David Rientjes Subject: Re: [PATCH 5/5] mm, compaction: more focused lru and pcplists draining References: <1412696019-21761-1-git-send-email-vbabka@suse.cz> <1412696019-21761-6-git-send-email-vbabka@suse.cz> In-Reply-To: <1412696019-21761-6-git-send-email-vbabka@suse.cz> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/07/2014 11:33 AM, Vlastimil Babka wrote: > The goal of memory compaction is to create high-order freepages through page > migration. Page migration however puts pages on the per-cpu lru_add cache, > which is later flushed to per-cpu pcplists, and only after pcplists are > drained the pages can actually merge. This can happen due to the per-cpu > caches becoming full through further freeing, or explicitly. > > During direct compaction, it is useful to do the draining explicitly so that > pages merge as soon as possible and compaction can detect success immediately > and keep the latency impact at minimum. However the current implementation is > far from ideal. Draining is done only in __alloc_pages_direct_compact(), > after all zones were already compacted, and the decisions to continue or stop > compaction in individual zones was done without the last batch of migrations > being merged. It is also missing the draining of lru_add cache before the > pcplists. > > This patch moves the draining for direct compaction into compact_zone(). It > adds the missing lru_cache draining and uses the newly introduced single zone > pcplists draining to reduce overhead and avoid impact on unrelated zones. > Draining is only performed when it can actually lead to merging of a page of > desired order (passed by cc->order). This means it is only done when migration > occurred in the previously scanned cc->order aligned block(s) and the > migration scanner is now pointing to the next cc->order aligned block. Acked-by: Rik van Riel