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 <iamjoonsoo.kim@lge.com>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Tested-by: Tony Lindgren <tony@atomide.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Aneesh Kumar K . V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Laura Abbott <lauraa@codeaurora.org>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Will Deacon <will.deacon@arm.com>
Cc: <linux-api@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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 @@
% 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 @@
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.
==============================================================
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index a0c9e45..32699b2 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -885,7 +885,7 @@ int min_free_kbytes_sysctl_handler(struct ctl_table *, int,
void __user *, size_t *, loff_t *);
int watermark_scale_factor_sysctl_handler(struct ctl_table *, int,
void __user *, size_t *, loff_t *);
-extern int sysctl_lowmem_reserve_ratio[MAX_NR_ZONES-1];
+extern int sysctl_lowmem_reserve_ratio[MAX_NR_ZONES];
int lowmem_reserve_ratio_sysctl_handler(struct ctl_table *, int,
void __user *, size_t *, loff_t *);
int percpu_pagelist_fraction_sysctl_handler(struct ctl_table *, int,
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index b046678..34a4c12 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -205,17 +205,18 @@ static void __free_pages_ok(struct page *page, unsigned int order);
* TBD: should special case ZONE_DMA32 machines here - in those we normally
* don't need any ZONE_NORMAL reservation
*/
-int sysctl_lowmem_reserve_ratio[MAX_NR_ZONES-1] = {
+int sysctl_lowmem_reserve_ratio[MAX_NR_ZONES] = {
#ifdef CONFIG_ZONE_DMA
- 256,
+ [ZONE_DMA] = 256,
#endif
#ifdef CONFIG_ZONE_DMA32
- 256,
+ [ZONE_DMA32] = 256,
#endif
+ [ZONE_NORMAL] = 32,
#ifdef CONFIG_HIGHMEM
- 32,
+ [ZONE_HIGHMEM] = 0,
#endif
- 32,
+ [ZONE_MOVABLE] = 0,
};
EXPORT_SYMBOL(totalram_pages);
@@ -7132,13 +7133,15 @@ static void setup_per_zone_lowmem_reserve(void)
struct zone *lower_zone;
idx--;
-
- if (sysctl_lowmem_reserve_ratio[idx] < 1)
- sysctl_lowmem_reserve_ratio[idx] = 1;
-
lower_zone = pgdat->node_zones + idx;
- lower_zone->lowmem_reserve[j] = managed_pages /
- sysctl_lowmem_reserve_ratio[idx];
+
+ if (sysctl_lowmem_reserve_ratio[idx] < 1) {
+ sysctl_lowmem_reserve_ratio[idx] = 0;
+ lower_zone->lowmem_reserve[j] = 0;
+ } else {
+ lower_zone->lowmem_reserve[j] =
+ managed_pages / sysctl_lowmem_reserve_ratio[idx];
+ }
managed_pages += lower_zone->managed_pages;
}
}
