linux-kernel - Re: [PATCH v4 4/7] Reclaim invalidated page ASAP

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Message-ID: <AANLkTikG1EAMm8yPvBVUXjFz1Bu9m+vfwH3TRPDzS9mq@mail.gmail.com>
Date:	Wed, 8 Dec 2010 17:16:01 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>,
	linux-mm <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Nick Piggin <npiggin@...nel.dk>
Subject: Re: [PATCH v4 4/7] Reclaim invalidated page ASAP

On Wed, Dec 8, 2010 at 5:04 PM, KOSAKI Motohiro
<kosaki.motohiro@...fujitsu.com> wrote:
>> invalidate_mapping_pages is very big hint to reclaimer.
>> It means user doesn't want to use the page any more.
>> So in order to prevent working set page eviction, this patch
>> move the page into tail of inactive list by PG_reclaim.
>>
>> Please, remember that pages in inactive list are working set
>> as well as active list. If we don't move pages into inactive list's
>> tail, pages near by tail of inactive list can be evicted although
>> we have a big clue about useless pages. It's totally bad.
>>
>> Now PG_readahead/PG_reclaim is shared.
>> fe3cba17 added ClearPageReclaim into clear_page_dirty_for_io for
>> preventing fast reclaiming readahead marker page.
>>
>> In this series, PG_reclaim is used by invalidated page, too.
>> If VM find the page is invalidated and it's dirty, it sets PG_reclaim
>> to reclaim asap. Then, when the dirty page will be writeback,
>> clear_page_dirty_for_io will clear PG_reclaim unconditionally.
>> It disturbs this serie's goal.
>>
>> I think it's okay to clear PG_readahead when the page is dirty, not
>> writeback time. So this patch moves ClearPageReadahead.
>>
>> Signed-off-by: Minchan Kim <minchan.kim@...il.com>
>> Acked-by: Rik van Riel <riel@...hat.com>
>> Acked-by: Mel Gorman <mel@....ul.ie>
>> Cc: Wu Fengguang <fengguang.wu@...el.com>
>> Cc: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
>> Cc: Johannes Weiner <hannes@...xchg.org>
>> Cc: Nick Piggin <npiggin@...nel.dk>
>
> Until anyone should data, I will not ack this. This patch increase
> VM state, but benefit is doubious.

Make sense to me. If Ben is busy, I will measure it and send the result.
Thanks!

-- 
Kind regards,
Minchan Kim
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