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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 /include/linux/swap.h
parente23ca00bf1b1c6c0f04702cb4d29e275ab8dc330 (diff)
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[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 'include/linux/swap.h')
-rw-r--r--include/linux/swap.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/swap.h b/include/linux/swap.h
index 54eac8a..5b1fdf1 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -155,6 +155,7 @@ extern void swapin_readahead(swp_entry_t, unsigned long, struct vm_area_struct *
/* linux/mm/page_alloc.c */
extern unsigned long totalram_pages;
extern unsigned long totalhigh_pages;
+extern unsigned long totalreserve_pages;
extern long nr_swap_pages;
extern unsigned int nr_free_pages(void);
extern unsigned int nr_free_pages_pgdat(pg_data_t *pgdat);
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