From cb45b0e966cbe747b6189c15b108901cc7d6c97c Mon Sep 17 00:00:00 2001 From: Hideo AOKI Date: Mon, 10 Apr 2006 22:52:59 -0700 Subject: [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 Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/swap.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/swap.h') diff --git a/include/linux/swap.h b/include/linux/swap.h index 54eac8a39a4c..5b1fdf1cff4f 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); -- cgit v1.2.3