Commit 0f9a921c authored by Rik van Riel's avatar Rik van Riel Committed by Mel Gorman

x86: mm: only do a local tlb flush in ptep_set_access_flags()

The function ptep_set_access_flags() is only ever invoked to set access
flags or add write permission on a PTE.  The write bit is only ever set
together with the dirty bit.

Because we only ever upgrade a PTE, it is safe to skip flushing entries on
remote TLBs. The worst that can happen is a spurious page fault on other
CPUs, which would flush that TLB entry.

Lazily letting another CPU incur a spurious page fault occasionally is
(much!) cheaper than aggressively flushing everybody else's TLB.
Signed-off-by: default avatarRik van Riel <riel@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Michel Lespinasse <walken@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
parent f4a75d2e
......@@ -301,6 +301,13 @@ void pgd_free(struct mm_struct *mm, pgd_t *pgd)
free_page((unsigned long)pgd);
}
/*
* Used to set accessed or dirty bits in the page table entries
* on other architectures. On x86, the accessed and dirty bits
* are tracked by hardware. However, do_wp_page calls this function
* to also make the pte writeable at the same time the dirty bit is
* set. In that case we do actually need to write the PTE.
*/
int ptep_set_access_flags(struct vm_area_struct *vma,
unsigned long address, pte_t *ptep,
pte_t entry, int dirty)
......@@ -310,7 +317,7 @@ int ptep_set_access_flags(struct vm_area_struct *vma,
if (changed && dirty) {
*ptep = entry;
pte_update_defer(vma->vm_mm, address, ptep);
flush_tlb_page(vma, address);
__flush_tlb_one(address);
}
return changed;
......
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