On Wed 08-07-20 16:19:17, Joonsoo Kim wrote: > On Tue, Jul 07, 2020 at 01:40:19PM +0200, Michal Hocko wrote: [...] > Subject: [PATCH] mm/migrate: clear __GFP_RECLAIM for THP allocation for > migration > > In migration target allocation functions, THP allocations uses different > gfp_mask, especially, in regard to the reclaim gfp_mask. There is no > reason to use different reclaim gfp_mask for each cases and it is > an obstacle to make a common function in order to clean-up migration > target allocation functions. This patch fixes this situation by using > common reclaim gfp_mask for THP allocation. I would find the following more understandable, feel free to reuse parts that you like: " new_page_nodemask is a migration callback and it tries to use a common gfp flags for the target page allocation whether it is a base page or a THP. The later only adds GFP_TRANSHUGE to the given mask. This results in the allocation being slightly more aggressive than necessary because the resulting gfp mask will contain also __GFP_RECLAIM_KSWAPD. THP allocations usually exclude this flag to reduce over eager background reclaim during a high THP allocation load which has been seen during large mmaps initialization. There is no indication that this is a problem for migration as well but theoretically the same might happen when migrating large mappings to a different node. Make the migration callback consistent with regular THP allocations. " -- Michal Hocko SUSE Labs
