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authorHideo AOKI <haoki@redhat.com>2006-04-10 22:52:59 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-04-11 06:18:32 -0700
commitcb45b0e966cbe747b6189c15b108901cc7d6c97c (patch)
tree0402d4809ec175e80b083f7a713ec32c0109baad /mm/page_alloc.c
parente23ca00bf1b1c6c0f04702cb4d29e275ab8dc330 (diff)
[PATCH] overcommit: add calculate_totalreserve_pages()
These patches are an enhancement of OVERCOMMIT_GUESS algorithm in __vm_enough_memory(). - why the kernel needed patching When the kernel can't allocate anonymous pages in practice, currnet OVERCOMMIT_GUESS could return success. This implementation might be the cause of oom kill in memory pressure situation. If the Linux runs with page reservation features like /proc/sys/vm/lowmem_reserve_ratio and without swap region, I think the oom kill occurs easily. - the overall design approach in the patch When the OVERCOMMET_GUESS algorithm calculates number of free pages, the reserved free pages are regarded as non-free pages. This change helps to avoid the pitfall that the number of free pages become less than the number which the kernel tries to keep free. - testing results I tested the patches using my test kernel module. If the patches aren't applied to the kernel, __vm_enough_memory() returns success in the situation but autual page allocation is failed. On the other hand, if the patches are applied to the kernel, memory allocation failure is avoided since __vm_enough_memory() returns failure in the situation. I checked that on i386 SMP 16GB memory machine. I haven't tested on nommu environment currently. This patch adds totalreserve_pages for __vm_enough_memory(). Calculate_totalreserve_pages() checks maximum lowmem_reserve pages and pages_high in each zone. Finally, the function stores the sum of each zone to totalreserve_pages. The totalreserve_pages is calculated when the VM is initilized. And the variable is updated when /proc/sys/vm/lowmem_reserve_raito or /proc/sys/vm/min_free_kbytes are changed. Signed-off-by: Hideo Aoki <haoki@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'mm/page_alloc.c')
-rw-r--r--mm/page_alloc.c39
1 files changed, 39 insertions, 0 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index b8165e037dee..97d6827c7d66 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -51,6 +51,7 @@ nodemask_t node_possible_map __read_mostly = NODE_MASK_ALL;
EXPORT_SYMBOL(node_possible_map);
unsigned long totalram_pages __read_mostly;
unsigned long totalhigh_pages __read_mostly;
+unsigned long totalreserve_pages __read_mostly;
long nr_swap_pages;
int percpu_pagelist_fraction;
@@ -2477,6 +2478,38 @@ void __init page_alloc_init(void)
}
/*
+ * calculate_totalreserve_pages - called when sysctl_lower_zone_reserve_ratio
+ * or min_free_kbytes changes.
+ */
+static void calculate_totalreserve_pages(void)
+{
+ struct pglist_data *pgdat;
+ unsigned long reserve_pages = 0;
+ int i, j;
+
+ for_each_online_pgdat(pgdat) {
+ for (i = 0; i < MAX_NR_ZONES; i++) {
+ struct zone *zone = pgdat->node_zones + i;
+ unsigned long max = 0;
+
+ /* Find valid and maximum lowmem_reserve in the zone */
+ for (j = i; j < MAX_NR_ZONES; j++) {
+ if (zone->lowmem_reserve[j] > max)
+ max = zone->lowmem_reserve[j];
+ }
+
+ /* we treat pages_high as reserved pages. */
+ max += zone->pages_high;
+
+ if (max > zone->present_pages)
+ max = zone->present_pages;
+ reserve_pages += max;
+ }
+ }
+ totalreserve_pages = reserve_pages;
+}
+
+/*
* setup_per_zone_lowmem_reserve - called whenever
* sysctl_lower_zone_reserve_ratio changes. Ensures that each zone
* has a correct pages reserved value, so an adequate number of
@@ -2507,6 +2540,9 @@ static void setup_per_zone_lowmem_reserve(void)
}
}
}
+
+ /* update totalreserve_pages */
+ calculate_totalreserve_pages();
}
/*
@@ -2561,6 +2597,9 @@ void setup_per_zone_pages_min(void)
zone->pages_high = zone->pages_min + tmp / 2;
spin_unlock_irqrestore(&zone->lru_lock, flags);
}
+
+ /* update totalreserve_pages */
+ calculate_totalreserve_pages();
}
/*