Hi Joonsoo, On Tue, Apr 11, 2017 at 12:17:14PM +0900, js1...@gmail.com wrote: > From: Joonsoo Kim <iamjoonsoo....@lge.com> > > 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. > > 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.ku...@linux.vnet.ibm.com> > Acked-by: Vlastimil Babka <vba...@suse.cz> > Signed-off-by: Joonsoo Kim <iamjoonsoo....@lge.com> > --- > include/linux/mmzone.h | 2 +- > mm/page_alloc.c | 11 ++++++----- > 2 files changed, 7 insertions(+), 6 deletions(-) > > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h > index ebaccd4..96194bf 100644 > --- a/include/linux/mmzone.h > +++ b/include/linux/mmzone.h > @@ -869,7 +869,7 @@ 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 32b31d6..60ffa4e 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] = INT_MAX, > #endif > - 32, > + [ZONE_MOVABLE] = INT_MAX, > };
We need to update lowmem_reserve_ratio in Documentation/sysctl/vm.txt. And to me, INT_MAX is rather awkward. # cat /proc/sys/vm/lowmem_reserve_ratio 256 256 32 2147483647 2147483647 What do you think about to use 0 or -1 as special meaning instead 2147483647? Anyway, it could be separate patch regardless of zone_cma so I hope Andrew to merge this patch regardless of other patches in this patchset. Thanks.