On Mon, Sep 11, 2023 at 03:41:43PM -0400, Johannes Weiner wrote: > The buddy allocator coalesces compatible blocks during freeing, but it > doesn't update the types of the subblocks to match. When an allocation > later breaks the chunk down again, its pieces will be put on freelists > of the wrong type. This encourages incompatible page mixing (ask for > one type, get another), and thus long-term fragmentation. > > Update the subblocks when merging a larger chunk, such that a later > expand() will maintain freelist type hygiene. > > v2: > - remove spurious change_pageblock_range() move (Zi Yan) > > Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx> I'm not 100% convinced on the amount of harm this causes but given that it's a relatively rare condition, I didn't think about the consequences too deeply. The patch certainly has merit so; Acked-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> -- Mel Gorman SUSE Labs
