From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754696AbaHFHaA (ORCPT ); Wed, 6 Aug 2014 03:30:00 -0400 Received: from LGEMRELSE6Q.lge.com ([156.147.1.121]:44077 "EHLO lgemrelse6q.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751323AbaHFH37 (ORCPT ); Wed, 6 Aug 2014 03:29:59 -0400 X-Original-SENDERIP: 10.177.220.145 X-Original-MAILFROM: iamjoonsoo.kim@lge.com Date: Wed, 6 Aug 2014 16:37:19 +0900 From: Joonsoo Kim To: Gioh Kim Cc: Andrew Morton , Marek Szyprowski , Minchan Kim , Laura Abbott , Michal Nazarewicz , Alexander Viro , Johannes Weiner , linux-kernel@vger.kernel.org, linux-mm@kvack.org, ????????? , "'Chanho Min'" Subject: Re: [PATCHv2] CMA/HOTPLUG: clear buffer-head lru before page migration Message-ID: <20140806073719.GA3590@js1304-P5Q-DELUXE> References: <53D9A86B.20208@lge.com> <20140731155703.a8bc3b77af913c8b3a63090a@linux-foundation.org> <53DADB56.3050103@lge.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <53DADB56.3050103@lge.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 01, 2014 at 09:12:06AM +0900, Gioh Kim wrote: > > > 2014-08-01 오전 7:57, Andrew Morton 쓴 글: > >On Thu, 31 Jul 2014 11:22:35 +0900 Gioh Kim wrote: > > > >>The previous PATCH inserts invalidate_bh_lrus() only into CMA code. > >>HOTPLUG needs also dropping bh of lru. > >>So v2 inserts invalidate_bh_lrus() into both of CMA and HOTPLUG. > >> > >> > >>---------------------------- 8< ---------------------------- > >>The bh must be free to migrate a page at which bh is mapped. > >>The reference count of bh is increased when it is installed > >>into lru so that the bh of lru must be freed before migrating the page. > >> > >>This frees every bh of lru. We could free only bh of migrating page. > >>But searching lru sometimes costs more than invalidating entire lru. > >> > >>Signed-off-by: Gioh Kim > >>Acked-by: Michal Nazarewicz > >>--- > >> mm/memory_hotplug.c | 1 + > >> mm/page_alloc.c | 2 ++ > >> 2 files changed, 3 insertions(+) > >> > >>diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > >>index a3797d3..1c5454f 100644 > >>--- a/mm/memory_hotplug.c > >>+++ b/mm/memory_hotplug.c > >>@@ -1672,6 +1672,7 @@ repeat: > >> lru_add_drain_all(); > >> cond_resched(); > >> drain_all_pages(); > >>+ invalidate_bh_lrus(); > > > >Both of these calls should have a comment explaining why > >invalidate_bh_lrus() is being called. > > > >> } > >> > >> pfn = scan_movable_pages(start_pfn, end_pfn); > >>diff --git a/mm/page_alloc.c b/mm/page_alloc.c > >>index b99643d4..c00dedf 100644 > >>--- a/mm/page_alloc.c > >>+++ b/mm/page_alloc.c > >>@@ -6369,6 +6369,8 @@ int alloc_contig_range(unsigned long start, unsigned long end, > >> if (ret) > >> return ret; > >> > >>+ invalidate_bh_lrus(); > >>+ > >> ret = __alloc_contig_migrate_range(&cc, start, end); > >> if (ret) > >> goto done; > > > >I do feel that this change is likely to be beneficial, but I don't want > >to apply such a patch until I know what its effects are upon all > >alloc_contig_range() callers. Especially hugetlb. > > I'm very sorry to hear that. > How can I check the effects? > Hello, Gioh. As you know, I generally agree this patch, but, I want to know that this patch really fixes your problem. There is some time difference between invalidate_bh_lrus() and migrate_page() so that the bh of the migrating page could be re-installed on bh lru again. Any remarkable success rate changes? If this time gap is critical, we should put this invalidation logic on other place. Thanks.