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| author | Johannes Weiner <hannes@cmpxchg.org> | 2012-01-12 17:18:40 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2012-01-12 20:13:06 -0800 |
| commit | 00c54c0bac24bb02d2460c516da76651a7451286 (patch) | |
| tree | d88356ab217fa4c119a6c11dd7f614413adc020a /mm | |
| parent | cfa449461e67b60df986170eecb089831fa9e49a (diff) | |
| download | linux-00c54c0bac24bb02d2460c516da76651a7451286.tar.gz linux-00c54c0bac24bb02d2460c516da76651a7451286.tar.bz2 linux-00c54c0bac24bb02d2460c516da76651a7451286.zip | |
mm: page_cgroup: check page_cgroup arrays in lookup_page_cgroup() only when necessary
lookup_page_cgroup() is usually used only against pages that are used in
userspace.
The exception is the CONFIG_DEBUG_VM-only memcg check from the page
allocator: it can run on pages without page_cgroup descriptors allocated
when the pages are fed into the page allocator for the first time during
boot or memory hotplug.
Include the array check only when CONFIG_DEBUG_VM is set and save the
unnecessary check in production kernels.
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/page_cgroup.c | 18 |
1 files changed, 16 insertions, 2 deletions
diff --git a/mm/page_cgroup.c b/mm/page_cgroup.c index f0559e049e00..e910524e5a08 100644 --- a/mm/page_cgroup.c +++ b/mm/page_cgroup.c @@ -28,9 +28,16 @@ struct page_cgroup *lookup_page_cgroup(struct page *page) struct page_cgroup *base; base = NODE_DATA(page_to_nid(page))->node_page_cgroup; +#ifdef CONFIG_DEBUG_VM + /* + * The sanity checks the page allocator does upon freeing a + * page can reach here before the page_cgroup arrays are + * allocated when feeding a range of pages to the allocator + * for the first time during bootup or memory hotplug. + */ if (unlikely(!base)) return NULL; - +#endif offset = pfn - NODE_DATA(page_to_nid(page))->node_start_pfn; return base + offset; } @@ -85,9 +92,16 @@ struct page_cgroup *lookup_page_cgroup(struct page *page) { unsigned long pfn = page_to_pfn(page); struct mem_section *section = __pfn_to_section(pfn); - +#ifdef CONFIG_DEBUG_VM + /* + * The sanity checks the page allocator does upon freeing a + * page can reach here before the page_cgroup arrays are + * allocated when feeding a range of pages to the allocator + * for the first time during bootup or memory hotplug. + */ if (!section->page_cgroup) return NULL; +#endif return section->page_cgroup + pfn; } |