On Wed 15-01-20 13:07:17, Mike Kravetz wrote: [...] > Summary > ======= > It 'looks' like the statement "MPOL_MF_STRICT is ignored on huge page > mappings." is left over from the original mbind implementation. When > the huge page migration support was added, I can not be sure if ignoring > MPOL_MF_STRICT for huge pages during the verify/isolation phase was > intentional. It seems like it was as the return value from > isolate_huge_page() is ignored. THanks for the tedious work of studying the mess^Whistory. > > What should we do? > ================== > 1) Nothing more than optimizations by Li Xinhai. Behavior that could be > seen as conflicting with man page has existed since v3.12 and I am > not aware of any complaints. > 2) In addition to optimizations by Li Xinhai, modify code to truly ignore > MPOL_MF_STRICT for huge page mappings. This would be fairly easy to do > after a failure of migrate_pages(). We could simply traverse the list > of pages that were not migrated looking for any non-hugetlb page. > 3) Remove the statement "MPOL_MF_STRICT is ignored on huge page mappings." > and modify code accordingly. > > My suggestion would be for 1 or 2. Thoughts? And why do we exactly need to do anything at all? There is an inconsistency that has been there for years without anybody noticing. NUMA API is a mess on its own and unfixable at this stage, there will always be some corner cases. If there is no real workload hitting this incosistency and suffering, I would rather not touch this at all. Unless the change would clean up the code or make it more maintainable. -- Michal Hocko SUSE Labs
