path: root/arch/x86/mm
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authorMel Gorman <mgorman@suse.de>2014-01-21 22:33:19 (GMT)
committerIngo Molnar <mingo@kernel.org>2014-01-25 08:10:43 (GMT)
commit71b54f8263860a37dd9f50f81880a9d681fd9c10 (patch)
treea300b589402aedecee5835170de898932be8d176 /arch/x86/mm
parent15aa368255f249df0b2af630c9487bb5471bd7da (diff)
x86/mm: Eliminate redundant page table walk during TLB range flushing
When choosing between doing an address space or ranged flush, the x86 implementation of flush_tlb_mm_range takes into account whether there are any large pages in the range. A per-page flush typically requires fewer entries than would covered by a single large page and the check is redundant. There is one potential exception. THP migration flushes single THP entries and it conceivably would benefit from flushing a single entry instead of the mm. However, this flush is after a THP allocation, copy and page table update potentially with any other threads serialised behind it. In comparison to that, the flush is noise. It makes more sense to optimise balancing to require fewer flushes than to optimise the flush itself. This patch deletes the redundant huge page check. Signed-off-by: Mel Gorman <mgorman@suse.de> Tested-by: Davidlohr Bueso <davidlohr@hp.com> Reviewed-by: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Cc: Alex Shi <alex.shi@linaro.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/n/tip-sgei1drpOcburujPsfh6ovmo@git.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/mm')
1 files changed, 1 insertions, 27 deletions
diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 5176526..dd8dda1 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -158,32 +158,6 @@ void flush_tlb_current_task(void)
- * It can find out the THP large page, or
- * HUGETLB page in tlb_flush when THP disabled
- */
-static inline unsigned long has_large_page(struct mm_struct *mm,
- unsigned long start, unsigned long end)
- pgd_t *pgd;
- pud_t *pud;
- pmd_t *pmd;
- unsigned long addr = ALIGN(start, HPAGE_SIZE);
- for (; addr < end; addr += HPAGE_SIZE) {
- pgd = pgd_offset(mm, addr);
- if (likely(!pgd_none(*pgd))) {
- pud = pud_offset(pgd, addr);
- if (likely(!pud_none(*pud))) {
- pmd = pmd_offset(pud, addr);
- if (likely(!pmd_none(*pmd)))
- if (pmd_large(*pmd))
- return addr;
- }
- }
- }
- return 0;
void flush_tlb_mm_range(struct mm_struct *mm, unsigned long start,
unsigned long end, unsigned long vmflag)
@@ -218,7 +192,7 @@ void flush_tlb_mm_range(struct mm_struct *mm, unsigned long start,
nr_base_pages = (end - start) >> PAGE_SHIFT;
/* tlb_flushall_shift is on balance point, details in commit log */
- if (nr_base_pages > act_entries || has_large_page(mm, start, end)) {
+ if (nr_base_pages > act_entries) {
} else {

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