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[PATCH 11/13] Bias the placement of kernel pages at lower pfns

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From: Mel Gorman <mel@...>
To: <akpm@...>
Cc: Mel Gorman <mel@...>, <linux-kernel@...>, <linux-mm@...>
Subject: [PATCH 11/13] Bias the placement of kernel pages at lower pfns
Date: Monday, September 10, 2007 - 7:23 am

Subject: Bias the placement of kernel pages at lower pfns

This patch chooses blocks with lower PFNs when placing kernel allocations.
This is particularly important during fallback in low memory situations to
stop unmovable pages being placed throughout the entire address space.

Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/page_alloc.c |   20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff -rup -X /usr/src/patchset-0.6/bin//dontdiff linux-2.6.23-rc5-010-bias-the-location-of-pages-freed-for-min_free_kbytes-in-the-same-max_order_nr_pages-blocks/mm/page_alloc.c linux-2.6.23-rc5-011-bias-the-placement-of-kernel-pages-at-lower-pfns/mm/page_alloc.c
--- linux-2.6.23-rc5-010-bias-the-location-of-pages-freed-for-min_free_kbytes-in-the-same-max_order_nr_pages-blocks/mm/page_alloc.c	2007-09-02 16:22:04.000000000 +0100
+++ linux-2.6.23-rc5-011-bias-the-placement-of-kernel-pages-at-lower-pfns/mm/page_alloc.c	2007-09-02 16:22:27.000000000 +0100
@@ -768,6 +768,23 @@ int move_freepages_block(struct zone *zo
 	return move_freepages(zone, start_page, end_page, migratetype);
 }
 
+/* Return the page with the lowest PFN in the list */
+static struct page *min_page(struct list_head *list)
+{
+	unsigned long min_pfn = -1UL;
+	struct page *min_page = NULL, *page;;
+
+	list_for_each_entry(page, list, lru) {
+		unsigned long pfn = page_to_pfn(page);
+		if (pfn < min_pfn) {
+			min_pfn = pfn;
+			min_page = page;
+		}
+	}
+
+	return min_page;
+}
+
 /* Remove an element from the buddy allocator from the fallback list */
 static struct page *__rmqueue_fallback(struct zone *zone, int order,
 						int start_migratetype)
@@ -791,8 +808,11 @@ static struct page *__rmqueue_fallback(s
 			if (list_empty(&area->free_list[migratetype]))
 				continue;
 
+			/* Bias kernel allocations towards low pfns */
 			page = list_entry(area->free_list[migratetype].next,
 					struct page, lru);
+			if (unlikely(start_migratetype != MIGRATE_MOVABLE))
+				page = min_page(&area->free_list[migratetype]);
 			area->nr_free--;
 
 			/*
-
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Messages in current thread:
[PATCH 0/13] Reduce external fragmentation by grouping pages..., Mel Gorman, (Mon Sep 10, 7:20 am)
Re: [PATCH 0/13] Reduce external fragmentation by grouping p..., Andrew Morton, (Thu Sep 13, 9:01 pm)
Re: [PATCH 0/13] Reduce external fragmentation by grouping p..., Mel Gorman, (Fri Sep 14, 10:33 am)
Re: [PATCH 0/13] Reduce external fragmentation by grouping p..., Andrew Morton, (Sun Sep 16, 6:34 am)
[PATCH 13/13] Print out statistics in relation to fragmentat..., Mel Gorman, (Mon Sep 10, 7:24 am)
[PATCH 12/13] Be more agressive about stealing when MIGRATE_..., Mel Gorman, (Mon Sep 10, 7:24 am)
[PATCH 11/13] Bias the placement of kernel pages at lower pfns, Mel Gorman, (Mon Sep 10, 7:23 am)
[PATCH 10/13] Bias the location of pages freed for min_free_..., Mel Gorman, (Mon Sep 10, 7:23 am)
[PATCH 9/13] Do not group pages by mobility type on low memo..., Mel Gorman, (Mon Sep 10, 7:23 am)
[PATCH 8/13] Move free pages between lists on steal, Mel Gorman, (Mon Sep 10, 7:22 am)
[PATCH 7/13] Drain per-cpu lists when high-order allocations..., Mel Gorman, (Mon Sep 10, 7:22 am)
Re: [PATCH 7/13] Drain per-cpu lists when high-order allocat..., Nick Piggin, (Mon Sep 10, 11:05 am)
Re: [PATCH 7/13] Drain per-cpu lists when high-order allocat..., Mel Gorman, (Tue Sep 11, 5:34 am)
[PATCH 6/13] Group short-lived and reclaimable kernel alloca..., Mel Gorman, (Mon Sep 10, 7:22 am)
Re: Group short-lived and reclaimable kernel allocations, Paul Jackson, (Mon Sep 10, 3:44 pm)
Re: Group short-lived and reclaimable kernel allocations, Mel Gorman, (Mon Sep 10, 5:15 pm)
[PATCH 5/13] Choose pages from the per cpu list-based on mig..., Mel Gorman, (Mon Sep 10, 7:21 am)
[PATCH 4/13] Split the free lists for movable and unmovable ..., Mel Gorman, (Mon Sep 10, 7:21 am)
[PATCH 3/13] Fix corruption of memmap on ia64-sparsemem when..., Mel Gorman, (Mon Sep 10, 7:21 am)
[PATCH 2/13] Add a bitmap that is used to track flags affect..., Mel Gorman, (Mon Sep 10, 7:20 am)
[PATCH 1/13] ia64: parse kernel parameter hugepagesz= in ear..., Mel Gorman, (Mon Sep 10, 7:20 am)