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From: Minchan Kim <minchan@kernel.org>
To: Mel Gorman <mgorman@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
	Marek Szyprowski <m.szyprowski@samsung.com>,
	Michal Nazarewicz <mina86@mina86.com>,
	Rik van Riel <riel@redhat.com>
Subject: Re: [PATCH 2/2] mm: support MIGRATE_DISCARD
Date: Thu, 6 Sep 2012 14:31:12 +0900	[thread overview]
Message-ID: <20120906053112.GA16231@bbox> (raw)
In-Reply-To: <20120905105611.GI11266@suse.de>

Hi Mel,

On Wed, Sep 05, 2012 at 11:56:11AM +0100, Mel Gorman wrote:
> On Wed, Sep 05, 2012 at 05:11:13PM +0900, Minchan Kim wrote:
> > This patch introudes MIGRATE_DISCARD mode in migration.
> > It drops *clean cache pages* instead of migration so that
> > migration latency could be reduced by avoiding (memcpy + page remapping).
> > It's useful for CMA because latency of migration is very important rather
> > than eviction of background processes's workingset. In addition, it needs
> > less free pages for migration targets so it could avoid memory reclaiming
> > to get free pages, which is another factor increase latency.
> > 
> 
> Bah, this was released while I was reviewing the older version. I did
> not read this one as closely but I see the enum problems have gone away
> at least. I'd still prefer if CMA had an additional helper to discard
> some pages with shrink_page_list() and migrate the remaining pages with
> migrate_pages(). That would remove the need to add a MIGRATE_DISCARD
> migrate mode at all.

I am not convinced with your point. What's the benefit on separating
reclaim and migration? For just removing MIGRATE_DISCARD mode?
I don't think it's not bad because my implementation is very simple(maybe
it's much simpler than separating reclaim and migration) and
could be used by others like memory-hotplug in future.
If you're not strong against with me, I would like to insist on my implementation.

> 
> -- 
> Mel Gorman
> SUSE Labs
> 
> --
> 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/ .
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-- 
Kind regards,
Minchan Kim

  reply	other threads:[~2012-09-06  5:29 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-09-05  8:11 [PATCH 1/2] mm: change enum migrate_mode with bitwise type Minchan Kim
2012-09-05  8:11 ` [PATCH 2/2] mm: support MIGRATE_DISCARD Minchan Kim
2012-09-05 10:56   ` Mel Gorman
2012-09-06  5:31     ` Minchan Kim [this message]
2012-09-06  8:29       ` Mel Gorman
2012-09-06  9:03         ` Mel Gorman
2012-09-07  0:57           ` Kyungmin Park
2012-09-07  2:26             ` Minchan Kim
2012-09-07  8:10               ` Mel Gorman
2012-09-07  2:24           ` Minchan Kim
2012-09-07  5:57             ` Kyungmin Park
2012-09-07  7:31               ` Kyungmin Park
2012-09-07  8:17                 ` Minchan Kim
2012-09-07  8:57                   ` Kyungmin Park
2012-09-07  8:21             ` Mel Gorman
2012-09-07  9:32               ` Mel Gorman
2012-09-08  0:16                 ` Minchan Kim
2012-09-05 12:43   ` Michal Nazarewicz
2012-12-21 13:04   ` lihanhui
2012-09-05 12:41 ` [PATCH 1/2] mm: change enum migrate_mode with bitwise type Michal Nazarewicz

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