Hello, Michal. Sorry for a really long delay. 2017-09-14 22:24 GMT+09:00 Michal Hocko <mhocko@xxxxxxxxxx>: > [Sorry for a later reply] > > On Wed 06-09-17 13:35:25, Joonsoo Kim 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. > > I am still not convinced this is a good idea. I do agree that reserving > memory in both HIGHMEM and MOVABLE is just wasting memory but removing > the reserve from the highmem as well will result that an oom victim will > allocate from lower zones and that might have unexpected side effects. Looks like you are confused. This patch only affects the situation that ZONE_HIGHMEM and ZONE_MOVABLE is used at the same time. In that case, before this patch, ZONE_HIGHMEM has reserve for GFP_HIGHMEM | GFP_MOVABLE request, but, with this patch, no reserve in ZONE_HIGHMEM for GFP_HIGHMEM | GFP_MOVABLE request. This perfectly matchs with your hope. :) > Can we simply leave HIGHMEM reserve and only remove it from the movable > zone if both are present? There is no higher zone than ZONE_MOVABLE so ZONE_MOVABLE has no reserve with/without this patch. To save memory, we need to remove the reserve in ZONE_HIGHMEM. Thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
