linux-kernel - [PATCH 3/4] mm: vmscan: Evaluate the watermarks against the correct classzone

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Message-Id: <1308922998-15529-4-git-send-email-mgorman@suse.de>
Date:	Fri, 24 Jun 2011 14:43:17 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Pádraig Brady <P@...igBrady.com>,
	James Bottomley <James.Bottomley@...senPartnership.com>,
	Colin King <colin.king@...onical.com>,
	Minchan Kim <minchan.kim@...il.com>,
	Andrew Lutomirski <luto@....edu>,
	Rik van Riel <riel@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	linux-mm <linux-mm@...ck.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Mel Gorman <mgorman@...e.de>
Subject: [PATCH 3/4] mm: vmscan: Evaluate the watermarks against the correct classzone

When deciding if kswapd is sleeping prematurely, the classzone is
taken into account but this is different to what balance_pgdat() and
the allocator are doing. Specifically, the DMA zone will be checked
based on the classzone used when waking kswapd which could be for a
GFP_KERNEL or GFP_HIGHMEM request. The lowmem reserve limit kicks in,
the watermark is not met and kswapd thinks its sleeping prematurely
keeping kswapd awake in error.

Reported-and-tested-by: Pádraig Brady <P@...igBrady.com>
Signed-off-by: Mel Gorman <mgorman@...e.de>
---
 mm/vmscan.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 38665ec..d859111 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2341,7 +2341,7 @@ static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining,
 		}
 
 		if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone),
-							classzone_idx, 0))
+							i, 0))
 			all_zones_ok = false;
 		else
 			balanced += zone->present_pages;
-- 
1.7.3.4

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