+CC linux-api On 09/06/2017 06:35 AM, js1304@xxxxxxxxx wrote: > From: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> > > 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 fix this situation by defining sysctl_lowmem_reserve_ratio > array by MAX_NR_ZONES and place "#ifdef" to right place. > > Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx> > Acked-by: Vlastimil Babka <vbabka@xxxxxxx> > Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> > --- > Documentation/sysctl/vm.txt | 5 ++--- > include/linux/mmzone.h | 2 +- > mm/page_alloc.c | 25 ++++++++++++++----------- > 3 files changed, 17 insertions(+), 15 deletions(-) > > diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt > index 9baf66a..e9059d3 100644 > --- a/Documentation/sysctl/vm.txt > +++ b/Documentation/sysctl/vm.txt > @@ -336,8 +336,6 @@ 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 > @@ -388,7 +386,8 @@ 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. > > ============================================================== > > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h > index 356a814..d549c4e 100644 > --- a/include/linux/mmzone.h > +++ b/include/linux/mmzone.h > @@ -890,7 +890,7 @@ 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 0f34356..2a7f7e9 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -203,17 +203,18 @@ 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); > @@ -6921,13 +6922,15 @@ 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; > } > } > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>