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authorEbru Akagunduz <ebru.akagunduz@gmail.com>2016-07-26 15:25:03 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2016-07-26 16:19:19 -0700
commit8a966ed746d63c8103d496da85973eeeec01d77f (patch)
treea96bcdb72409c34910440549c2e4fa248a468c4e /mm/huge_memory.c
parent70652f6ec0566ae6b4147d88c6d043c68484227f (diff)
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mm: make swapin readahead to improve thp collapse rate
This patch makes swapin readahead to improve thp collapse rate. When khugepaged scanned pages, there can be a few of the pages in swap area. With the patch THP can collapse 4kB pages into a THP when there are up to max_ptes_swap swap ptes in a 2MB range. The patch was tested with a test program that allocates 400B of memory, writes to it, and then sleeps. I force the system to swap out all. Afterwards, the test program touches the area by writing, it skips a page in each 20 pages of the area. Without the patch, system did not swap in readahead. THP rate was %65 of the program of the memory, it did not change over time. With this patch, after 10 minutes of waiting khugepaged had collapsed %99 of the program's memory. [kirill.shutemov@linux.intel.com: trivial cleanup of exit path of the function] [kirill.shutemov@linux.intel.com: __collapse_huge_page_swapin(): drop unused 'pte' parameter] [kirill.shutemov@linux.intel.com: do not hold anon_vma lock during swap in] Signed-off-by: Ebru Akagunduz <ebru.akagunduz@gmail.com> Acked-by: Rik van Riel <riel@redhat.com> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Xie XiuQi <xiexiuqi@huawei.com> Cc: Cyrill Gorcunov <gorcunov@openvz.org> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: David Rientjes <rientjes@google.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@suse.cz> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/huge_memory.c')
-rw-r--r--mm/huge_memory.c43
1 files changed, 40 insertions, 3 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index ed474483a620..b11351579e7a 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2373,6 +2373,44 @@ static bool hugepage_vma_check(struct vm_area_struct *vma)
return !(vma->vm_flags & VM_NO_THP);
}
+/*
+ * Bring missing pages in from swap, to complete THP collapse.
+ * Only done if khugepaged_scan_pmd believes it is worthwhile.
+ *
+ * Called and returns without pte mapped or spinlocks held,
+ * but with mmap_sem held to protect against vma changes.
+ */
+
+static void __collapse_huge_page_swapin(struct mm_struct *mm,
+ struct vm_area_struct *vma,
+ unsigned long address, pmd_t *pmd)
+{
+ unsigned long _address;
+ pte_t *pte, pteval;
+ int swapped_in = 0, ret = 0;
+
+ pte = pte_offset_map(pmd, address);
+ for (_address = address; _address < address + HPAGE_PMD_NR*PAGE_SIZE;
+ pte++, _address += PAGE_SIZE) {
+ pteval = *pte;
+ if (!is_swap_pte(pteval))
+ continue;
+ swapped_in++;
+ ret = do_swap_page(mm, vma, _address, pte, pmd,
+ FAULT_FLAG_ALLOW_RETRY|FAULT_FLAG_RETRY_NOWAIT,
+ pteval);
+ if (ret & VM_FAULT_ERROR) {
+ trace_mm_collapse_huge_page_swapin(mm, swapped_in, 0);
+ return;
+ }
+ /* pte is unmapped now, we need to map it */
+ pte = pte_offset_map(pmd, _address);
+ }
+ pte--;
+ pte_unmap(pte);
+ trace_mm_collapse_huge_page_swapin(mm, swapped_in, 1);
+}
+
static void collapse_huge_page(struct mm_struct *mm,
unsigned long address,
struct page **hpage,
@@ -2440,6 +2478,8 @@ static void collapse_huge_page(struct mm_struct *mm,
goto out;
}
+ __collapse_huge_page_swapin(mm, vma, address, pmd);
+
anon_vma_lock_write(vma->anon_vma);
pte = pte_offset_map(pmd, address);
@@ -2516,9 +2556,6 @@ static void collapse_huge_page(struct mm_struct *mm,
result = SCAN_SUCCEED;
out_up_write:
up_write(&mm->mmap_sem);
- trace_mm_collapse_huge_page(mm, isolated, result);
- return;
-
out_nolock:
trace_mm_collapse_huge_page(mm, isolated, result);
return;