On Tue, Jan 26, 2021 at 02:59:17PM -0800, Minchan Kim wrote: > The release buffer_head in LRU is great improvement for migration > point of view. > > A question: > > Can't we invalidate(e.g., invalidate_bh_lrus) bh_lru in migrate_prep or > elsewhere when migration found the failure and is about to retry? > > Migration has done such a way for other per-cpu stuffs for a long time, > which would be more consistent with others and might be faster sometimes > with reducing IPI calls for page. Should lru_add_drain_all() also handle draining the buffer lru for all callers? A quick survey ... invalidate_bdev() already calls invalidate_bh_lrus() compact_nodes() would probably benefit from the BH LRU being invalidated POSIX_FADV_DONTNEED would benefit if the underlying filesystem uses BHs check_and_migrate_cma_pages() would benefit khugepaged_do_scan() doesn't need it today scan_get_next_rmap_item() looks like it only works on anon pages (?) so doesn't need it mem_cgroup_force_empty() probably needs it mem_cgroup_move_charge() ditto memfd_wait_for_pins() doesn't need it shake_page() might benefit offline_pages() would benefit alloc_contig_range() would benefit Seems like most would benefit and a few won't care. I think I'd lean towards having lru_add_drain_all() call invalidate_bh_lrus(), just to simplify things.
