linux-kernel - Re: [PATCH v2 06/10] vmscan: make isolate_lru

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Message-ID: <20110531134609.GB4594@cmpxchg.org>
Date:	Tue, 31 May 2011 15:46:09 +0200
From:	Johannes Weiner <hannes@...xchg.org>
To:	Minchan Kim <minchan.kim@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-mm <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>,
	Andrea Arcangeli <aarcange@...hat.com>
Subject: Re: [PATCH v2 06/10] vmscan: make isolate_lru_page with filter aware

On Mon, May 30, 2011 at 03:13:45AM +0900, Minchan Kim wrote:
> In __zone_reclaim case, we don't want to shrink mapped page.
> Nonetheless, we have isolated mapped page and re-add it into
> LRU's head. It's unnecessary CPU overhead and makes LRU churning.
> 
> Of course, when we isolate the page, the page might be mapped but
> when we try to migrate the page, the page would be not mapped.
> So it could be migrated. But race is rare and although it happens,
> it's no big deal.
> 
> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> Acked-by: Johannes Weiner <hannes@...xchg.org>
> Cc: Mel Gorman <mgorman@...e.de>
> Cc: Rik van Riel <riel@...hat.com>
> Cc: Andrea Arcangeli <aarcange@...hat.com>
> Signed-off-by: Minchan Kim <minchan.kim@...il.com>
> ---
>  mm/vmscan.c |   29 +++++++++++++++++++++--------
>  1 files changed, 21 insertions(+), 8 deletions(-)
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 9972356..39941c7 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1395,6 +1395,7 @@ shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone,
>  	unsigned long nr_taken;
>  	unsigned long nr_anon;
>  	unsigned long nr_file;
> +	enum ISOLATE_PAGE_MODE mode = ISOLATE_NONE;
>  
>  	while (unlikely(too_many_isolated(zone, file, sc))) {
>  		congestion_wait(BLK_RW_ASYNC, HZ/10);
> @@ -1406,13 +1407,20 @@ shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone,
>  
>  	set_reclaim_mode(priority, sc, false);
>  	lru_add_drain();
> +
> +	if (!sc->may_unmap)
> +		mode |= ISOLATE_UNMAPPED;
> +	if (!sc->may_writepage)
> +		mode |= ISOLATE_CLEAN;
> +	mode |= sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ?
> +				ISOLATE_BOTH : ISOLATE_INACTIVE;

Hmm, it would probably be cleaner to fully convert the isolation mode
into independent flags.  INACTIVE, ACTIVE, BOTH is currently a
tri-state among flags, which is a bit ugly.

	mode = ISOLATE_INACTIVE;
	if (!sc->may_unmap)
		mode |= ISOLATE_UNMAPPED;
	if (!sc->may_writepage)
		mode |= ISOLATE_CLEAN;
	if (sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM)
		mode |= ISOLATE_ACTIVE;

What do you think?
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