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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 /Documentation/isdn | |
parent | e23ca00bf1b1c6c0f04702cb4d29e275ab8dc330 (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 'Documentation/isdn')
0 files changed, 0 insertions, 0 deletions