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From: Mel Gorman <mgorman@suse.de>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Dave Hansen <dave.hansen@intel.com>,
	Rik van Riel <riel@redhat.com>, Michal Hocko <mhocko@suse.cz>,
	Linux-MM <linux-mm@kvack.org>,
	LKML <linux-kernel@vger.kernel.org>, Mel Gorman <mgorman@suse.de>
Subject: [PATCH 2/6] mm: page_alloc: Document why NR_ALLOC_BATCH is always updated
Date: Wed, 18 Dec 2013 19:41:59 +0000	[thread overview]
Message-ID: <1387395723-25391-3-git-send-email-mgorman@suse.de> (raw)
In-Reply-To: <1387395723-25391-1-git-send-email-mgorman@suse.de>

From: Johannes Weiner <hannes@cmpxchg.org>

Needs-signed-off
---
 mm/page_alloc.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index f861d02..61e9e8c 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1547,7 +1547,15 @@ again:
 					  get_pageblock_migratetype(page));
 	}
 
+	/*
+	 * All allocations eat into the round-robin batch, even
+	 * allocations that are not subject to round-robin placement
+	 * themselves.  This makes sure that allocations that ARE
+	 * subject to round-robin placement compensate for the
+	 * allocations that aren't, to have equal placement overall.
+	 */
 	__mod_zone_page_state(zone, NR_ALLOC_BATCH, -(1 << order));
+
 	__count_zone_vm_events(PGALLOC, zone, 1 << order);
 	zone_statistics(preferred_zone, zone, gfp_flags);
 	local_irq_restore(flags);
-- 
1.8.4

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  parent reply	other threads:[~2013-12-18 19:42 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-12-18 19:41 [RFC PATCH 0/6] Configurable fair allocation zone policy v4 Mel Gorman
2013-12-18 19:41 ` [PATCH 1/6] mm: page_alloc: exclude unreclaimable allocations from zone fairness policy Mel Gorman
2013-12-18 19:41 ` Mel Gorman [this message]
2013-12-18 19:42 ` [PATCH 3/6] mm: page_alloc: Break out zone page aging distribution into its own helper Mel Gorman
2013-12-18 19:42 ` [PATCH 4/6] mm: page_alloc: Use zone node IDs to approximate locality Mel Gorman
2013-12-18 19:42 ` [PATCH 5/6] mm: Annotate page cache allocations Mel Gorman
2013-12-18 19:42 ` [PATCH 6/6] mm: page_alloc: Make zone distribution page aging policy configurable Mel Gorman
2013-12-18 21:06 ` [RFC PATCH 0/6] Configurable fair allocation zone policy v4 Johannes Weiner
2013-12-19 13:12   ` Michal Hocko
2013-12-19 13:29   ` Mel Gorman

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