Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752885AbaGNG4j (ORCPT ); Mon, 14 Jul 2014 02:56:39 -0400 Received: from lgeamrelo04.lge.com ([156.147.1.127]:55057 "EHLO lgeamrelo04.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751311AbaGNG4b (ORCPT ); Mon, 14 Jul 2014 02:56:31 -0400 X-Original-SENDERIP: 10.177.220.145 X-Original-MAILFROM: iamjoonsoo.kim@lge.com Date: Mon, 14 Jul 2014 16:02:25 +0900 From: Joonsoo Kim To: Michal Nazarewicz Cc: Andrew Morton , Gioh Kim , Laura Abbott , Marek Szyprowski , Alexander Viro , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, =?utf-8?B?7J206rG07Zi4?= , Gi-Oh Kim Subject: Re: [PATCH] [RFC] CMA: clear buffer-head lru before page migration Message-ID: <20140714070225.GE11317@js1304-P5Q-DELUXE> References: <53B664E5.5060102@lge.com> <20140707155252.15e81dff6683393ba3590478@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: 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 Tue, Jul 08, 2014 at 06:46:31PM +0200, Michal Nazarewicz wrote: > On Mon, Jul 07 2014, Andrew Morton wrote: > > What I proposed is that CMA call invalidate_bh_lrus() right at the > > outset. Something along the lines of > > > > --- a/mm/page_alloc.c~a > > +++ a/mm/page_alloc.c > > @@ -6329,6 +6329,14 @@ int alloc_contig_range(unsigned long sta > > }; > > INIT_LIST_HEAD(&cc.migratepages); > > > > +#ifdef CONFIG_CMA > > + /* > > + * Comment goes here > > + */ > > + if (migratetype == MIGRATE_CMA) > > + invalidate_bh_lrus(); > > +#endif > > + > > This seems reasonable, except I think it should go after > start_isolate_page_range call because otherwise there's no guarantee > that someone won't grab those pages back. > > Also to avoid the #ifdef perhaps we want this as well: I think that we just want to remove ifdef CONFIG_CMA on above code snippet, because invalidate_bh_lrus() would also help user of alloc_contig_range() with MIGRATE_MOVABLE. > > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h > index 6cbd1b6..2640a55 100644 > --- a/include/linux/mmzone.h > +++ b/include/linux/mmzone.h > @@ -64,10 +64,11 @@ enum { > }; > > #ifdef CONFIG_CMA > -# define is_migrate_cma(migratetype) unlikely((migratetype) == MIGRATE_CMA) > +# define __is_migrate_cma(migratetype) ((migratetype) == MIGRATE_CMA) > #else > -# define is_migrate_cma(migratetype) false > +# define __is_migrate_cma(migratetype) false > #endif > +#define is_migrate_cma(migratetype) unlikely(__is_migrate_cma(migratetype)) > > #define for_each_migratetype_order(order, type) \ > for (order = 0; order < MAX_ORDER; order++) \ > > and then use “if (__is_migrate_cma(migratetype))”. > > > /* > > * What we do here is we mark all pageblocks in range as > > * MIGRATE_ISOLATE. Because pageblock and max order pages may > > > > > > - I'd have thought that it would make sense to do this for huge pages > > as well (MIGRATE_MOVABLE) but nobody really seems to know. > > > > - There's a patch floating around ("Allow increasing the buffer-head > > per-CPU LRU size") which will double the size of the bh lrus, so this > > all becomes more important. > > > > - alloc_contig_range() does lru_add_drain_all() and drain_all_pages() > > *after* performing the allocation. I can't work out why this is the > > case and of course it is undocumented. If this is indeed not a bug > > then probably the invalidate_bh_lrus() should happen in the same > > place. > > The purpose is to get free non-buddy pages (so pages on PCP lists for > instance) back onto the buddy list. It's safe to move those calls above > the call to __alloc_contig_migrate_range, but I don't think it will > change anything (except of course the fact that if migration fails, > we'll do the draining for nothing). At a glance, we don't need that drain_all_pages(), because drain_all_pages() is also called by set_migratetype_isolate() after changing migratetype. And, it is better to move up lru_add_drain_all() to ahead of __alloc_contig_migrate_range(), because some pages could be skipped to migrate due to this lru page caching mechanism. Thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/