From: Ebru Akagunduz <ebru.akagunduz@xxxxxxxxx>
Subject: 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@xxxxxxxxxxxxxxx: trivial cleanup of exit path of the function]
[kirill.shutemov@xxxxxxxxxxxxxxx: __collapse_huge_page_swapin(): drop unused 'pte' parameter]
[kirill.shutemov@xxxxxxxxxxxxxxx: do not hold anon_vma lock during swap in]
Signed-off-by: Ebru Akagunduz <ebru.akagunduz@xxxxxxxxx>
Acked-by: Rik van Riel <riel@xxxxxxxxxx>
Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Xie XiuQi <xiexiuqi@xxxxxxxxxx>
Cc: Cyrill Gorcunov <gorcunov@xxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxx>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/trace/events/huge_memory.h | 24 +++++++++++++++
mm/huge_memory.c | 43 +++++++++++++++++++++++++--
mm/internal.h | 4 ++
mm/memory.c | 2 -
4 files changed, 69 insertions(+), 4 deletions(-)
diff -puN include/trace/events/huge_memory.h~mm-make-swapin-readahead-to-improve-thp-collapse-rate include/trace/events/huge_memory.h
--- a/include/trace/events/huge_memory.h~mm-make-swapin-readahead-to-improve-thp-collapse-rate
+++ a/include/trace/events/huge_memory.h
@@ -135,5 +135,29 @@ TRACE_EVENT(mm_collapse_huge_page_isolat
__print_symbolic(__entry->status, SCAN_STATUS))
);
+TRACE_EVENT(mm_collapse_huge_page_swapin,
+
+ TP_PROTO(struct mm_struct *mm, int swapped_in, int ret),
+
+ TP_ARGS(mm, swapped_in, ret),
+
+ TP_STRUCT__entry(
+ __field(struct mm_struct *, mm)
+ __field(int, swapped_in)
+ __field(int, ret)
+ ),
+
+ TP_fast_assign(
+ __entry->mm = mm;
+ __entry->swapped_in = swapped_in;
+ __entry->ret = ret;
+ ),
+
+ TP_printk("mm=%p, swapped_in=%d, ret=%d",
+ __entry->mm,
+ __entry->swapped_in,
+ __entry->ret)
+);
+
#endif /* __HUGE_MEMORY_H */
#include <trace/define_trace.h>
diff -puN mm/huge_memory.c~mm-make-swapin-readahead-to-improve-thp-collapse-rate mm/huge_memory.c
--- a/mm/huge_memory.c~mm-make-swapin-readahead-to-improve-thp-collapse-rate
+++ a/mm/huge_memory.c
@@ -2373,6 +2373,44 @@ static bool hugepage_vma_check(struct vm
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
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
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;
diff -puN mm/internal.h~mm-make-swapin-readahead-to-improve-thp-collapse-rate mm/internal.h
--- a/mm/internal.h~mm-make-swapin-readahead-to-improve-thp-collapse-rate
+++ a/mm/internal.h
@@ -36,6 +36,10 @@
/* Do not use these with a slab allocator */
#define GFP_SLAB_BUG_MASK (__GFP_DMA32|__GFP_HIGHMEM|~__GFP_BITS_MASK)
+extern int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
+ unsigned long address, pte_t *page_table, pmd_t *pmd,
+ unsigned int flags, pte_t orig_pte);
+
void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct *start_vma,
unsigned long floor, unsigned long ceiling);
diff -puN mm/memory.c~mm-make-swapin-readahead-to-improve-thp-collapse-rate mm/memory.c
--- a/mm/memory.c~mm-make-swapin-readahead-to-improve-thp-collapse-rate
+++ a/mm/memory.c
@@ -2522,7 +2522,7 @@ EXPORT_SYMBOL(unmap_mapping_range);
* We return with the mmap_sem locked or unlocked in the same cases
* as does filemap_fault().
*/
-static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
+int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long address, pte_t *page_table, pmd_t *pmd,
unsigned int flags, pte_t orig_pte)
{
_
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