The patch titled Subject: mm,unmap: avoid flushing TLB in batch if PTE is inaccessible has been added to the -mm mm-unstable branch. Its filename is mmunmap-avoid-flushing-tlb-in-batch-if-pte-is-inaccessible.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mmunmap-avoid-flushing-tlb-in-batch-if-pte-is-inaccessible.patch This patch will later appear in the mm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Huang Ying <ying.huang@xxxxxxxxx> Subject: mm,unmap: avoid flushing TLB in batch if PTE is inaccessible Date: Mon, 10 Apr 2023 15:52:24 +0800 0Day/LKP reported a performance regression for commit 7e12beb8ca2a ("migrate_pages: batch flushing TLB"). In the commit, the TLB flushing during page migration is batched. So, in try_to_migrate_one(), ptep_clear_flush() is replaced with set_tlb_ubc_flush_pending(). In further investigation, it is found that the TLB flushing can be avoided in ptep_clear_flush() if the PTE is inaccessible. In fact, we can optimize in similar way for the batched TLB flushing too to improve the performance. So in this patch, we check pte_accessible() before set_tlb_ubc_flush_pending() in try_to_unmap/migrate_one(). Tests show that the benchmark score of the anon-cow-rand-mt test case of vm-scalability test suite can improve up to 2.1% with the patch on a Intel server machine. The TLB flushing IPI can reduce up to 44.3%. Link: https://lore.kernel.org/oe-lkp/202303192325.ecbaf968-yujie.liu@xxxxxxxxx Link: https://lore.kernel.org/oe-lkp/ab92aaddf1b52ede15e2c608696c36765a2602c1.camel@xxxxxxxxx/ Link: https://lkml.kernel.org/r/20230410075224.827740-1-ying.huang@xxxxxxxxx Fixes: 7e12beb8ca2a ("migrate_pages: batch flushing TLB") Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx> Reported-by: kernel test robot <yujie.liu@xxxxxxxxx> Reviewed-by: Nadav Amit <namit@xxxxxxxxxx> Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> Cc: David Hildenbrand <david@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/rmap.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/mm/rmap.c~mmunmap-avoid-flushing-tlb-in-batch-if-pte-is-inaccessible +++ a/mm/rmap.c @@ -1580,7 +1580,8 @@ static bool try_to_unmap_one(struct foli */ pteval = ptep_get_and_clear(mm, address, pvmw.pte); - set_tlb_ubc_flush_pending(mm, pte_dirty(pteval)); + if (pte_accessible(mm, pteval)) + set_tlb_ubc_flush_pending(mm, pte_dirty(pteval)); } else { pteval = ptep_clear_flush(vma, address, pvmw.pte); } @@ -1961,7 +1962,8 @@ static bool try_to_migrate_one(struct fo */ pteval = ptep_get_and_clear(mm, address, pvmw.pte); - set_tlb_ubc_flush_pending(mm, pte_dirty(pteval)); + if (pte_accessible(mm, pteval)) + set_tlb_ubc_flush_pending(mm, pte_dirty(pteval)); } else { pteval = ptep_clear_flush(vma, address, pvmw.pte); } _ Patches currently in -mm which might be from ying.huang@xxxxxxxxx are migrate_pages_batch-fix-statistics-for-longterm-pin-retry.patch mmunmap-avoid-flushing-tlb-in-batch-if-pte-is-inaccessible.patch