path: root/mm/swap_state.c
diff options
authorHuang Ying <ying.huang@intel.com>2017-09-06 16:24:33 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2017-09-06 17:27:29 -0700
commitc4fa63092f216737b60c789968371d9960a598e5 (patch)
treec68329a01a3925a41522ab8ea6b3ae437d97185c /mm/swap_state.c
parentmm, swap: add swap readahead hit statistics (diff)
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@intel.com Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Rik van Riel <riel@redhat.com> Cc: Shaohua Li <shli@kernel.org> Cc: Hugh Dickins <hughd@google.com> Cc: Fengguang Wu <fengguang.wu@intel.com> Cc: Tim Chen <tim.c.chen@intel.com> Cc: Dave Hansen <dave.hansen@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/swap_state.c')
1 files changed, 11 insertions, 7 deletions
diff --git a/mm/swap_state.c b/mm/swap_state.c
index d1bdb31cab13..a901afe9da61 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -498,7 +498,7 @@ struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask,
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_t entry, gfp_t gfp_mask,
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)
- 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);
+ }