On Thu, Aug 24, 2017 at 11:41:58AM +0200, Vlastimil Babka wrote: > On 08/24/2017 07:45 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. > > > > 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> > > Looks like I did that almost year ago, so definitely had to refresh my > memory now :) > > Anyway now I looked more thoroughly and noticed that this change leaks > into the reported sysctl. On a 64bit system with ZONE_MOVABLE: > > before the patch: > vm.lowmem_reserve_ratio = 256 256 32 > > after the patch: > vm.lowmem_reserve_ratio = 256 256 32 2147483647 > > So if we indeed remove HIGHMEM from protection (c.f. Michal's mail), we > should do that differently than with the INT_MAX trick, IMHO. Hmm, this is already pointed by Minchan and I have answered that. lkml.kernel.org/r/<20170421013243.GA13966@js1304-desktop> If you have a better idea, please let me know. Thanks. -- 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>
