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authorHuang Ying <ying.huang@intel.com>2016-10-07 17:00:21 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2016-10-07 18:46:28 -0700
commitf6ab1f7f6b2d8e48c5fc47746a67363b20d79a1d (patch)
tree4a4891c1882f4cffb2b78ddcb0069ea069e5c439 /mm/swap_state.c
parentmm: fix cache mode tracking in vm_insert_mixed() (diff)
downloadlinux-dev-f6ab1f7f6b2d8e48c5fc47746a67363b20d79a1d.tar.xz
linux-dev-f6ab1f7f6b2d8e48c5fc47746a67363b20d79a1d.zip
mm, swap: use offset of swap entry as key of swap cache
This patch is to improve the performance of swap cache operations when the type of the swap device is not 0. Originally, the whole swap entry value is used as the key of the swap cache, even though there is one radix tree for each swap device. If the type of the swap device is not 0, the height of the radix tree of the swap cache will be increased unnecessary, especially on 64bit architecture. For example, for a 1GB swap device on the x86_64 architecture, the height of the radix tree of the swap cache is 11. But if the offset of the swap entry is used as the key of the swap cache, the height of the radix tree of the swap cache is 4. The increased height causes unnecessary radix tree descending and increased cache footprint. This patch reduces the height of the radix tree of the swap cache via using the offset of the swap entry instead of the whole swap entry value as the key of the swap cache. In 32 processes sequential swap out test case on a Xeon E5 v3 system with RAM disk as swap, the lock contention for the spinlock of the swap cache is reduced from 20.15% to 12.19%, when the type of the swap device is 1. Use the whole swap entry as key, perf-profile.calltrace.cycles-pp._raw_spin_lock_irq.__add_to_swap_cache.add_to_swap_cache.add_to_swap.shrink_page_list: 10.37, perf-profile.calltrace.cycles-pp._raw_spin_lock_irqsave.__remove_mapping.shrink_page_list.shrink_inactive_list.shrink_node_memcg: 9.78, Use the swap offset as key, perf-profile.calltrace.cycles-pp._raw_spin_lock_irq.__add_to_swap_cache.add_to_swap_cache.add_to_swap.shrink_page_list: 6.25, perf-profile.calltrace.cycles-pp._raw_spin_lock_irqsave.__remove_mapping.shrink_page_list.shrink_inactive_list.shrink_node_memcg: 5.94, Link: http://lkml.kernel.org/r/1473270649-27229-1-git-send-email-ying.huang@intel.com Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@kernel.org> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Hugh Dickins <hughd@google.com> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Minchan Kim <minchan@kernel.org> Cc: Aaron Lu <aaron.lu@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')
-rw-r--r--mm/swap_state.c8
1 files changed, 4 insertions, 4 deletions
diff --git a/mm/swap_state.c b/mm/swap_state.c
index 8679c997eab6..35d7e0ee1c77 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -94,7 +94,7 @@ int __add_to_swap_cache(struct page *page, swp_entry_t entry)
address_space = swap_address_space(entry);
spin_lock_irq(&address_space->tree_lock);
error = radix_tree_insert(&address_space->page_tree,
- entry.val, page);
+ swp_offset(entry), page);
if (likely(!error)) {
address_space->nrpages++;
__inc_node_page_state(page, NR_FILE_PAGES);
@@ -145,7 +145,7 @@ void __delete_from_swap_cache(struct page *page)
entry.val = page_private(page);
address_space = swap_address_space(entry);
- radix_tree_delete(&address_space->page_tree, page_private(page));
+ radix_tree_delete(&address_space->page_tree, swp_offset(entry));
set_page_private(page, 0);
ClearPageSwapCache(page);
address_space->nrpages--;
@@ -283,7 +283,7 @@ struct page * lookup_swap_cache(swp_entry_t entry)
{
struct page *page;
- page = find_get_page(swap_address_space(entry), entry.val);
+ page = find_get_page(swap_address_space(entry), swp_offset(entry));
if (page) {
INC_CACHE_INFO(find_success);
@@ -310,7 +310,7 @@ struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
* called after lookup_swap_cache() failed, re-calling
* that would confuse statistics.
*/
- found_page = find_get_page(swapper_space, entry.val);
+ found_page = find_get_page(swapper_space, swp_offset(entry));
if (found_page)
break;