The patch titled
Subject: mm, swap: fix swap readahead marking
has been added to the -mm tree. Its filename is
mm-swap-fix-swap-readahead-marking.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-swap-fix-swap-readahead-marking.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-swap-fix-swap-readahead-marking.patch
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------------------------------------------------------
From: Huang Ying <ying.huang@xxxxxxxxx>
Subject: mm, swap: fix swap readahead marking
In the original implementation, it is possible that the existing pages in
the swap cache (not newly readahead) could be marked as the readahead
pages. This will cause the statistics of swap readahead be wrong and
influence the swap readahead algorithm too.
This is fixed via marking a page as the readahead page only if it is newly
allocated and read from the disk.
When testing with linpack, after the fixing the swap readahead hit rate
increased from ~66% to ~86%.
Link: http://lkml.kernel.org/r/20170807054038.1843-3-ying.huang@xxxxxxxxx
Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Shaohua Li <shli@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Fengguang Wu <fengguang.wu@xxxxxxxxx>
Cc: Tim Chen <tim.c.chen@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/swap_state.c | 18 +++++++++++-------
1 file changed, 11 insertions(+), 7 deletions(-)
diff -puN mm/swap_state.c~mm-swap-fix-swap-readahead-marking mm/swap_state.c
--- a/mm/swap_state.c~mm-swap-fix-swap-readahead-marking
+++ a/mm/swap_state.c
@@ -498,7 +498,7 @@ struct page *swapin_readahead(swp_entry_
unsigned long start_offset, end_offset;
unsigned long mask;
struct blk_plug plug;
- bool do_poll = true;
+ bool do_poll = true, page_allocated;
mask = swapin_nr_pages(offset) - 1;
if (!mask)
@@ -514,14 +514,18 @@ struct page *swapin_readahead(swp_entry_
blk_start_plug(&plug);
for (offset = start_offset; offset <= end_offset ; offset++) {
/* Ok, do the async read-ahead now */
- page = read_swap_cache_async(swp_entry(swp_type(entry), offset),
- gfp_mask, vma, addr, false);
+ page = __read_swap_cache_async(
+ swp_entry(swp_type(entry), offset),
+ gfp_mask, vma, addr, &page_allocated);
if (!page)
continue;
- if (offset != entry_offset &&
- likely(!PageTransCompound(page))) {
- SetPageReadahead(page);
- count_vm_event(SWAP_RA);
+ if (page_allocated) {
+ swap_readpage(page, false);
+ if (offset != entry_offset &&
+ likely(!PageTransCompound(page))) {
+ SetPageReadahead(page);
+ count_vm_event(SWAP_RA);
+ }
}
put_page(page);
}
_
Patches currently in -mm which might be from ying.huang@xxxxxxxxx are
mm-thp-swap-support-to-clear-swap-cache-flag-for-thp-swapped-out.patch
mm-thp-swap-support-to-reclaim-swap-space-for-thp-swapped-out.patch
mm-thp-swap-support-to-reclaim-swap-space-for-thp-swapped-out-fix.patch
mm-thp-swap-make-reuse_swap_page-works-for-thp-swapped-out.patch
mm-thp-swap-make-reuse_swap_page-works-for-thp-swapped-out-fix.patch
mm-thp-swap-dont-allocate-huge-cluster-for-file-backed-swap-device.patch
block-thp-make-block_device_operationsrw_page-support-thp.patch
test-code-to-write-thp-to-swap-device-as-a-whole.patch
mm-thp-swap-support-to-split-thp-for-thp-swapped-out.patch
memcg-thp-swap-support-move-mem-cgroup-charge-for-thp-swapped-out.patch
memcg-thp-swap-avoid-to-duplicated-charge-thp-in-swap-cache.patch
memcg-thp-swap-make-mem_cgroup_swapout-support-thp.patch
mm-thp-swap-delay-splitting-thp-after-swapped-out.patch
mm-thp-swap-add-thp-swapping-out-fallback-counting.patch
mm-swap-add-swap-readahead-hit-statistics.patch
mm-swap-fix-swap-readahead-marking.patch
mm-swap-vma-based-swap-readahead.patch
mm-swap-add-sysfs-interface-for-vma-based-swap-readahead.patch
mm-swap-dont-use-vma-based-swap-readahead-if-hdd-is-used-as-swap.patch
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