From d3cda2337bbc9edd2a26b83cb00eaa8c048ff274 Mon Sep 17 00:00:00 2001 From: Joonsoo Kim Date: Tue, 10 Apr 2018 16:30:11 -0700 Subject: mm/page_alloc: don't reserve ZONE_HIGHMEM for ZONE_MOVABLE request Freepage on ZONE_HIGHMEM doesn't work for kernel memory so it's not that important to reserve. When ZONE_MOVABLE is used, this problem would theorectically cause to decrease usable memory for GFP_HIGHUSER_MOVABLE allocation request which is mainly used for page cache and anon page allocation. So, fix it by setting 0 to sysctl_lowmem_reserve_ratio[ZONE_HIGHMEM]. And, defining sysctl_lowmem_reserve_ratio array by MAX_NR_ZONES - 1 size makes code complex. For example, if there is highmem system, following reserve ratio is activated for *NORMAL ZONE* which would be easyily misleading people. #ifdef CONFIG_HIGHMEM 32 #endif This patch also fixes this situation by defining sysctl_lowmem_reserve_ratio array by MAX_NR_ZONES and place "#ifdef" to right place. Link: http://lkml.kernel.org/r/1504672525-17915-1-git-send-email-iamjoonsoo.kim@lge.com Signed-off-by: Joonsoo Kim Reviewed-by: Aneesh Kumar K.V Acked-by: Vlastimil Babka Tested-by: Tony Lindgren Cc: Michal Hocko Cc: Vlastimil Babka Cc: Mel Gorman Cc: Johannes Weiner Cc: "Aneesh Kumar K . V" Cc: Minchan Kim Cc: Rik van Riel Cc: Laura Abbott Cc: Marek Szyprowski Cc: Michal Nazarewicz Cc: Russell King Cc: Will Deacon Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/sysctl/vm.txt | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) (limited to 'Documentation') diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt index ff234d2..17256f2 100644 --- a/Documentation/sysctl/vm.txt +++ b/Documentation/sysctl/vm.txt @@ -312,8 +312,6 @@ The lowmem_reserve_ratio is an array. You can see them by reading this file. % cat /proc/sys/vm/lowmem_reserve_ratio 256 256 32 - -Note: # of this elements is one fewer than number of zones. Because the highest - zone's value is not necessary for following calculation. But, these values are not used directly. The kernel calculates # of protection pages for each zones from them. These are shown as array of protection pages @@ -364,7 +362,8 @@ As above expression, they are reciprocal number of ratio. pages of higher zones on the node. If you would like to protect more pages, smaller values are effective. -The minimum value is 1 (1/1 -> 100%). +The minimum value is 1 (1/1 -> 100%). The value less than 1 completely +disables protection of the pages. ============================================================== -- cgit v1.1