On Thu, Nov 05, 2020 at 04:55:37PM +0800, Alex Shi wrote: > From: Hugh Dickins <hughd@xxxxxxxxxx> > > It is necessary for page_idle_get_page() to recheck PageLRU() after > get_page_unless_zero(), but holding lru_lock around that serves no > useful purpose, and adds to lru_lock contention: delete it. > > See https://lore.kernel.org/lkml/20150504031722.GA2768@blaptop for the > discussion that led to lru_lock there; but __page_set_anon_rmap() now > uses WRITE_ONCE(), and I see no other risk in page_idle_clear_pte_refs() > using rmap_walk() (beyond the risk of racing PageAnon->PageKsm, mostly > but not entirely prevented by page_count() check in ksm.c's > write_protect_page(): that risk being shared with page_referenced() and > not helped by lru_lock). > > Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx> > Signed-off-by: Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx> > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx> > Cc: Vlastimil Babka <vbabka@xxxxxxx> > Cc: Minchan Kim <minchan@xxxxxxxxxx> > Cc: Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx> > Cc: linux-mm@xxxxxxxxx > Cc: linux-kernel@xxxxxxxxxxxxxxx Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
