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author | Hideo AOKI <haoki@redhat.com> | 2006-04-10 22:52:59 -0700 |
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committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-04-11 06:18:32 -0700 |
commit | cb45b0e966cbe747b6189c15b108901cc7d6c97c (patch) | |
tree | 0402d4809ec175e80b083f7a713ec32c0109baad /mm/page_alloc.c | |
parent | e23ca00bf1b1c6c0f04702cb4d29e275ab8dc330 (diff) | |
download | linux-stable-cb45b0e966cbe747b6189c15b108901cc7d6c97c.tar.gz linux-stable-cb45b0e966cbe747b6189c15b108901cc7d6c97c.tar.bz2 linux-stable-cb45b0e966cbe747b6189c15b108901cc7d6c97c.zip |
[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.c | 39 |
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(); } /* |