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mm: Only flush TLBs if a transhuge PMD is modified for NUMA pte scanning

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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>
This commit is contained in:
Mel Gorman 2013-10-07 11:28:49 +01:00 committed by Ingo Molnar
parent e920e14ca2
commit f123d74abf
2 changed files with 26 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

19
mm/huge_memory.c
View File

@ -1458,6 +1458,12 @@ int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma,
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;

14
mm/mprotect.c
View File

@ -144,10 +144,16 @@ static inline unsigned long change_pmd_range(struct vm_area_struct *vma,
if (pmd_trans_huge(*pmd)) {
if (next - addr != HPAGE_PMD_SIZE)
split_huge_page_pmd(vma, addr, pmd);
else if (change_huge_pmd(vma, pmd, addr, newprot,
prot_numa)) {
pages++;
continue;
else {
int nr_ptes = change_huge_pmd(vma, pmd, addr,
newprot, prot_numa);
if (nr_ptes) {
if (nr_ptes == HPAGE_PMD_NR)
pages++;
continue;
}
}
/* fall through */
}