On Wed, Jan 27, 2021 at 02:59:22AM +0000, Matthew Wilcox wrote: > 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. Fair enough.
