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authorMel Gorman <mgorman@suse.de>2013-10-07 11:28:49 +0100
committerIngo Molnar <mingo@kernel.org>2013-10-09 12:39:49 +0200
commitf123d74abf91574837d14e5ea58f6a779a387bf5 (patch)
tree4347ff38dea6a74a53d811e63c21e805a5d25cfd /mm/huge_memory.c
parente920e14ca29b0b2a981cfc90e4e20edd6f078d19 (diff)
mm: Only flush TLBs if a transhuge PMD is modified for NUMA pte scanning
NUMA PTE scanning is expensive both in terms of the scanning itself and the TLB flush if there are any updates. The TLB flush is avoided if no PTEs are updated but there is a bug where transhuge PMDs are considered to be updated even if they were already pmd_numa. This patch addresses the problem and TLB flushes should be reduced. Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Reviewed-by: Rik van Riel <riel@redhat.com> Signed-off-by: Mel Gorman <mgorman@suse.de> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1381141781-10992-12-git-send-email-mgorman@suse.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'mm/huge_memory.c')
-rw-r--r--mm/huge_memory.c19
1 files changed, 16 insertions, 3 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index d4928769680f..de8d5cfc2bf2 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1458,6 +1458,12 @@ out:
return ret;
}
+/*
+ * Returns
+ * - 0 if PMD could not be locked
+ * - 1 if PMD was locked but protections unchange and TLB flush unnecessary
+ * - HPAGE_PMD_NR is protections changed and TLB flush necessary
+ */
int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
unsigned long addr, pgprot_t newprot, int prot_numa)
{
@@ -1466,9 +1472,11 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
if (__pmd_trans_huge_lock(pmd, vma) == 1) {
pmd_t entry;
- entry = pmdp_get_and_clear(mm, addr, pmd);
+ ret = 1;
if (!prot_numa) {
+ entry = pmdp_get_and_clear(mm, addr, pmd);
entry = pmd_modify(entry, newprot);
+ ret = HPAGE_PMD_NR;
BUG_ON(pmd_write(entry));
} else {
struct page *page = pmd_page(*pmd);
@@ -1476,12 +1484,17 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
/* only check non-shared pages */
if (page_mapcount(page) == 1 &&
!pmd_numa(*pmd)) {
+ entry = pmdp_get_and_clear(mm, addr, pmd);
entry = pmd_mknuma(entry);
+ ret = HPAGE_PMD_NR;
}
}
- set_pmd_at(mm, addr, pmd, entry);
+
+ /* Set PMD if cleared earlier */
+ if (ret == HPAGE_PMD_NR)
+ set_pmd_at(mm, addr, pmd, entry);
+
spin_unlock(&vma->vm_mm->page_table_lock);
- ret = 1;
}
return ret;