From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx171.postini.com [74.125.245.171]) by kanga.kvack.org (Postfix) with SMTP id D37686B0031 for ; Thu, 25 Jul 2013 02:51:15 -0400 (EDT) Received: by mail-pb0-f53.google.com with SMTP id xb12so375721pbc.26 for ; Wed, 24 Jul 2013 23:51:15 -0700 (PDT) Message-ID: <51F0CACE.7040609@gmail.com> Date: Thu, 25 Jul 2013 14:50:54 +0800 From: Paul Bolle MIME-Version: 1.0 Subject: Re: [patch 3/3] mm: page_alloc: fair zone allocator policy References: <1374267325-22865-1-git-send-email-hannes@cmpxchg.org> <1374267325-22865-4-git-send-email-hannes@cmpxchg.org> <51ED9433.60707@redhat.com> In-Reply-To: <51ED9433.60707@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Rik van Riel Cc: Johannes Weiner , Andrew Morton , Mel Gorman , Andrea Arcangeli , linux-mm@kvack.org, linux-kernel@vger.kernel.org On 07/23/2013 04:21 AM, Rik van Riel wrote: > On 07/19/2013 04:55 PM, Johannes Weiner wrote: > >> @@ -1984,7 +1992,8 @@ this_zone_full: >> goto zonelist_scan; >> } >> >> - if (page) >> + if (page) { >> + atomic_sub(1U << order, &zone->alloc_batch); >> /* >> * page->pfmemalloc is set when ALLOC_NO_WATERMARKS was >> * necessary to allocate the page. The expectation is > > Could this be moved into the slow path in buffered_rmqueue and > rmqueue_bulk, or would the effect of ignoring the pcp buffers be > too detrimental to keeping the balance between zones? > > It would be kind of nice to not have this atomic operation on every > page allocation... atomic operation will lock cache line or memory bus? And cmpxchg will lock cache line or memory bus? ;-) > > As a side benefit, higher-order buffered_rmqueue and rmqueue_bulk > both happen under the zone->lock, so moving this accounting down > to that layer might allow you to get rid of the atomics alltogether. > > I like the overall approach though. This is something Linux has needed > for a long time, and could be extremely useful to automatic NUMA > balancing as well... > -- 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