diff options
author | Dave Hansen <dave@linux.vnet.ibm.com> | 2011-03-22 16:32:56 -0700 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2011-03-22 17:44:04 -0700 |
commit | 033193275b3ffcfe7f3fde7b569f3d207f6cd6a0 (patch) | |
tree | fc65fa02248f855f0f63e087f35a507b6abb5617 | |
parent | 278df9f451dc71dcd002246be48358a473504ad0 (diff) | |
download | linux-stable-033193275b3ffcfe7f3fde7b569f3d207f6cd6a0.tar.gz linux-stable-033193275b3ffcfe7f3fde7b569f3d207f6cd6a0.tar.bz2 linux-stable-033193275b3ffcfe7f3fde7b569f3d207f6cd6a0.zip |
pagewalk: only split huge pages when necessary
Right now, if a mm_walk has either ->pte_entry or ->pmd_entry set, it will
unconditionally split any transparent huge pages it runs in to. In
practice, that means that anyone doing a
cat /proc/$pid/smaps
will unconditionally break down every huge page in the process and depend
on khugepaged to re-collapse it later. This is fairly suboptimal.
This patch changes that behavior. It teaches each ->pmd_entry handler
(there are five) that they must break down the THPs themselves. Also, the
_generic_ code will never break down a THP unless a ->pte_entry handler is
actually set.
This means that the ->pmd_entry handlers can now choose to deal with THPs
without breaking them down.
[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Dave Hansen <dave@linux.vnet.ibm.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Acked-by: David Rientjes <rientjes@google.com>
Reviewed-by: Eric B Munson <emunson@mgebm.net>
Tested-by: Eric B Munson <emunson@mgebm.net>
Cc: Michael J Wolf <mjwolf@us.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matt Mackall <mpm@selenic.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r-- | fs/proc/task_mmu.c | 6 | ||||
-rw-r--r-- | include/linux/mm.h | 3 | ||||
-rw-r--r-- | mm/memcontrol.c | 5 | ||||
-rw-r--r-- | mm/pagewalk.c | 24 |
4 files changed, 32 insertions, 6 deletions
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index 60b914860f81..78fd3621f565 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -343,6 +343,8 @@ static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, struct page *page; int mapcount; + split_huge_page_pmd(walk->mm, pmd); + pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); for (; addr != end; pte++, addr += PAGE_SIZE) { ptent = *pte; @@ -467,6 +469,8 @@ static int clear_refs_pte_range(pmd_t *pmd, unsigned long addr, spinlock_t *ptl; struct page *page; + split_huge_page_pmd(walk->mm, pmd); + pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); for (; addr != end; pte++, addr += PAGE_SIZE) { ptent = *pte; @@ -623,6 +627,8 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, pte_t *pte; int err = 0; + split_huge_page_pmd(walk->mm, pmd); + /* find the first VMA at or above 'addr' */ vma = find_vma(walk->mm, addr); for (; addr != end; addr += PAGE_SIZE) { diff --git a/include/linux/mm.h b/include/linux/mm.h index 901435e3a9a9..294104e0891d 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -914,6 +914,9 @@ unsigned long unmap_vmas(struct mmu_gather **tlb, * @pgd_entry: if set, called for each non-empty PGD (top-level) entry * @pud_entry: if set, called for each non-empty PUD (2nd-level) entry * @pmd_entry: if set, called for each non-empty PMD (3rd-level) entry + * this handler is required to be able to handle + * pmd_trans_huge() pmds. They may simply choose to + * split_huge_page() instead of handling it explicitly. * @pte_entry: if set, called for each non-empty PTE (4th-level) entry * @pte_hole: if set, called for each hole at all levels * @hugetlb_entry: if set, called for each hugetlb entry diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 9e0f05efd114..e1ee6ad9c971 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -4763,7 +4763,8 @@ static int mem_cgroup_count_precharge_pte_range(pmd_t *pmd, pte_t *pte; spinlock_t *ptl; - VM_BUG_ON(pmd_trans_huge(*pmd)); + split_huge_page_pmd(walk->mm, pmd); + pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); for (; addr != end; pte++, addr += PAGE_SIZE) if (is_target_pte_for_mc(vma, addr, *pte, NULL)) @@ -4925,8 +4926,8 @@ static int mem_cgroup_move_charge_pte_range(pmd_t *pmd, pte_t *pte; spinlock_t *ptl; + split_huge_page_pmd(walk->mm, pmd); retry: - VM_BUG_ON(pmd_trans_huge(*pmd)); pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); for (; addr != end; addr += PAGE_SIZE) { pte_t ptent = *(pte++); diff --git a/mm/pagewalk.c b/mm/pagewalk.c index 7cfa6ae02303..c3450d533611 100644 --- a/mm/pagewalk.c +++ b/mm/pagewalk.c @@ -33,19 +33,35 @@ static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end, pmd = pmd_offset(pud, addr); do { +again: next = pmd_addr_end(addr, end); - split_huge_page_pmd(walk->mm, pmd); - if (pmd_none_or_clear_bad(pmd)) { + if (pmd_none(*pmd)) { if (walk->pte_hole) err = walk->pte_hole(addr, next, walk); if (err) break; continue; } + /* + * This implies that each ->pmd_entry() handler + * needs to know about pmd_trans_huge() pmds + */ if (walk->pmd_entry) err = walk->pmd_entry(pmd, addr, next, walk); - if (!err && walk->pte_entry) - err = walk_pte_range(pmd, addr, next, walk); + if (err) + break; + + /* + * Check this here so we only break down trans_huge + * pages when we _need_ to + */ + if (!walk->pte_entry) + continue; + + split_huge_page_pmd(walk->mm, pmd); + if (pmd_none_or_clear_bad(pmd)) + goto again; + err = walk_pte_range(pmd, addr, next, walk); if (err) break; } while (pmd++, addr = next, addr != end); |