Ryan tried to enable the large folio for anonymous mapping [1]. Unlike large folio for page cache which doesn't trigger frequent page allocation/free, large folio for anonymous mapping is allocated/freeed more frequently. So large folio for anonymous mapping exposes some lock contention. Ryan mentioned the deferred queue lock in [1]. We also met other two lock contention: lru lock and zone lock. This series tries to mitigate the deferred queue lock and reduce lru lock in some level. The patch1 tries to reduce deferred queue lock by not acquiring queue lock when check whether the folio is in deferred list or not. Test page fault1 of will-it-scale showed 60% deferred queue lock contention reduction. The patch2 tries to reduce lru lock by allowing batched add large folio to lru list. Test page fault1 of will-it-scale showed 20% lru lock contention reduction. The zone lock contention happens on large folio free path and related with commit f26b3fa04611 "mm/page_alloc: limit number of high-order pages on PCP during bulk free" and will not be address by this series. [1] https://lore.kernel.org/linux-mm/20230414130303.2345383-1-ryan.roberts@xxxxxxx/ Yin Fengwei (2): THP: avoid lock when check whether THP is in deferred list lru: allow large batched add large folio to lru list include/linux/pagevec.h | 19 +++++++++++++++++-- mm/huge_memory.c | 19 ++++++++++++++++--- mm/swap.c | 3 +-- 3 files changed, 34 insertions(+), 7 deletions(-) -- 2.30.2
