From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f180.google.com (mail-pd0-f180.google.com [209.85.192.180]) by kanga.kvack.org (Postfix) with ESMTP id 78F366B003A for ; Wed, 7 May 2014 17:15:37 -0400 (EDT) Received: by mail-pd0-f180.google.com with SMTP id y10so1523726pdj.39 for ; Wed, 07 May 2014 14:15:37 -0700 (PDT) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTP id ke1si14448130pad.91.2014.05.07.14.15.36 for ; Wed, 07 May 2014 14:15:36 -0700 (PDT) Date: Wed, 7 May 2014 14:15:34 -0700 From: Andrew Morton Subject: Re: [patch v3 2/6] mm, compaction: return failed migration target pages back to freelist Message-Id: <20140507141534.d4def933b3a9999e7826df5c@linux-foundation.org> In-Reply-To: References: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: David Rientjes Cc: Mel Gorman , Rik van Riel , Vlastimil Babka , Joonsoo Kim , Greg Thelen , Hugh Dickins , linux-kernel@vger.kernel.org, linux-mm@kvack.org On Tue, 6 May 2014 19:22:43 -0700 (PDT) David Rientjes wrote: > Memory compaction works by having a "freeing scanner" scan from one end of a > zone which isolates pages as migration targets while another "migrating scanner" > scans from the other end of the same zone which isolates pages for migration. > > When page migration fails for an isolated page, the target page is returned to > the system rather than the freelist built by the freeing scanner. This may > require the freeing scanner to continue scanning memory after suitable migration > targets have already been returned to the system needlessly. > > This patch returns destination pages to the freeing scanner freelist when page > migration fails. This prevents unnecessary work done by the freeing scanner but > also encourages memory to be as compacted as possible at the end of the zone. > > Reported-by: Greg Thelen What did Greg actually report? IOW, what if any observable problem is being fixed here? -- 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