mm: free compound page with correct order
Compound page should be freed by put_page() or free_pages() with correct
order. Not doing so will cause tail pages leaked.
The compound order can be obtained by compound_order() or use
HPAGE_PMD_ORDER in our case. Some people would argue the latter is
faster but I prefer the former which is more general.
This bug was observed not just on our servers (the worst case we saw is
11G leaked on a 48G machine) but also on our workstations running Ubuntu
based distro.
$ cat /proc/vmstat | grep thp_zero_page_alloc
thp_zero_page_alloc 55
thp_zero_page_alloc_failed 0
This means there is (thp_zero_page_alloc - 1) * (2M - 4K) memory leaked.
Fixes: 97ae17497e
("thp: implement refcounting for huge zero page")
Signed-off-by: Yu Zhao <yuzhao@google.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: David Rientjes <rientjes@google.com>
Cc: Bob Liu <lliubbo@gmail.com>
Cc: <stable@vger.kernel.org> [3.8+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
parent
f601de2044
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@ -200,7 +200,7 @@ retry:
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preempt_disable();
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if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
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preempt_enable();
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__free_page(zero_page);
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__free_pages(zero_page, compound_order(zero_page));
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goto retry;
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}
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@ -232,7 +232,7 @@ static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
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if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
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struct page *zero_page = xchg(&huge_zero_page, NULL);
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BUG_ON(zero_page == NULL);
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__free_page(zero_page);
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__free_pages(zero_page, compound_order(zero_page));
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return HPAGE_PMD_NR;
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}
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