linux-kernel - Re: [PATCH] vmscan: Do reclaim stall in case of mlocked page.

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Message-ID: <20110831173031.GA21571@redhat.com>
Date:	Wed, 31 Aug 2011 19:30:31 +0200
From:	Johannes Weiner <jweiner@...hat.com>
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>,
	Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Subject: Re: [PATCH] vmscan: Do reclaim stall in case of mlocked page.

On Tue, Nov 15, 2011 at 12:37:23AM +0900, Minchan Kim wrote:
> [1] made avoid unnecessary reclaim stall when second shrink_page_list(ie, synchronous
> shrink_page_list) try to reclaim page_list which has not-dirty pages.
> But it seems rather awkawrd on unevictable page.
> The unevictable page in shrink_page_list would be moved into unevictable lru from page_list.
> So it would be not on page_list when shrink_page_list returns.
> Nevertheless it skips reclaim stall.
>
> This patch fixes it so that it can do reclaim stall in case of mixing mlocked pages
> and writeback pages on page_list.
> 
> [1] 7d3579e,vmscan: narrow the scenarios in whcih lumpy reclaim uses synchrounous reclaim

Lumpy isolates physically contiguous in the hope to free a bunch of
pages that can be merged to a bigger page.  If an unevictable page is
encountered, the chance of that is gone.  Why invest the allocation
latency when we know it won't pay off anymore?
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