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| author | Huang Ying <ying.huang@intel.com> | 2023-04-24 14:54:08 +0800 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2023-04-27 13:42:16 -0700 |
| commit | 4d4b6d66db63ceed399f1fb1a4b24081d2590eb1 (patch) | |
| tree | a92cbb17d4be5951c437e3bbc6b7544d63cdee5b | |
| parent | 01106e140835ff94fdef79d66f166b87b0c89824 (diff) | |
| download | lwn-4d4b6d66db63ceed399f1fb1a4b24081d2590eb1.tar.gz lwn-4d4b6d66db63ceed399f1fb1a4b24081d2590eb1.zip | |
mm,unmap: avoid flushing TLB in batch if PTE is inaccessible
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@intel.com
Link: https://lore.kernel.org/oe-lkp/ab92aaddf1b52ede15e2c608696c36765a2602c1.camel@intel.com/
Link: https://lkml.kernel.org/r/20230424065408.188498-1-ying.huang@intel.com
Fixes: 7e12beb8ca2a ("migrate_pages: batch flushing TLB")
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Reported-by: kernel test robot <yujie.liu@intel.com>
Reviewed-by: Nadav Amit <namit@vmware.com>
Reviewed-by: Xin Hao <xhao@linux.alibaba.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
| -rw-r--r-- | mm/rmap.c | 12 |
1 files changed, 8 insertions, 4 deletions
diff --git a/mm/rmap.c b/mm/rmap.c index ba901c416785..19392e090bec 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -642,10 +642,14 @@ void try_to_unmap_flush_dirty(void) #define TLB_FLUSH_BATCH_PENDING_LARGE \ (TLB_FLUSH_BATCH_PENDING_MASK / 2) -static void set_tlb_ubc_flush_pending(struct mm_struct *mm, bool writable) +static void set_tlb_ubc_flush_pending(struct mm_struct *mm, pte_t pteval) { struct tlbflush_unmap_batch *tlb_ubc = ¤t->tlb_ubc; int batch; + bool writable = pte_dirty(pteval); + + if (!pte_accessible(mm, pteval)) + return; arch_tlbbatch_add_mm(&tlb_ubc->arch, mm); tlb_ubc->flush_required = true; @@ -729,7 +733,7 @@ void flush_tlb_batched_pending(struct mm_struct *mm) } } #else -static void set_tlb_ubc_flush_pending(struct mm_struct *mm, bool writable) +static void set_tlb_ubc_flush_pending(struct mm_struct *mm, pte_t pteval) { } @@ -1580,7 +1584,7 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, */ pteval = ptep_get_and_clear(mm, address, pvmw.pte); - set_tlb_ubc_flush_pending(mm, pte_dirty(pteval)); + set_tlb_ubc_flush_pending(mm, pteval); } else { pteval = ptep_clear_flush(vma, address, pvmw.pte); } @@ -1961,7 +1965,7 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma, */ pteval = ptep_get_and_clear(mm, address, pvmw.pte); - set_tlb_ubc_flush_pending(mm, pte_dirty(pteval)); + set_tlb_ubc_flush_pending(mm, pteval); } else { pteval = ptep_clear_flush(vma, address, pvmw.pte); } |