On Tue, Apr 13, 2021 at 02:24:12PM -0700, Yang Shi wrote: > When the THP NUMA fault support was added THP migration was not supported yet. > So the ad hoc THP migration was implemented in NUMA fault handling. Since v4.14 > THP migration has been supported so it doesn't make too much sense to still keep > another THP migration implementation rather than using the generic migration > code. > > This patch reworked the NUMA fault handling to use generic migration implementation > to migrate misplaced page. There is no functional change. > > After the refactor the flow of NUMA fault handling looks just like its > PTE counterpart: > Acquire ptl > Prepare for migration (elevate page refcount) > Release ptl > Isolate page from lru and elevate page refcount > Migrate the misplaced THP > > If migration is failed just restore the old normal PMD. > > In the old code anon_vma lock was needed to serialize THP migration > against THP split, but since then the THP code has been reworked a lot, > it seems anon_vma lock is not required anymore to avoid the race. > > The page refcount elevation when holding ptl should prevent from THP > split. > > Use migrate_misplaced_page() for both base page and THP NUMA hinting > fault and remove all the dead and duplicate code. > > Signed-off-by: Yang Shi <shy828301@xxxxxxxxx> I did not spot any big problems and FWIW, the series overall passed a series of tests that exercise NUMA balancing migrations so... Acked-by: Mel Gorman <mgorman@xxxxxxx> -- Mel Gorman SUSE Labs
