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| author | Dan Williams <dan.j.williams@intel.com> | 2019-05-15 00:41:35 +0200 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-05-15 04:52:48 +0200 |
| commit | 97500a4a54876d3d6d2d1b8419223eb4e69b32d8 (patch) | |
| tree | 2b9362cd0411e7ef29e6dd45d4189cc6fa0f58fb /mm/shuffle.h | |
| parent | mm: move buddy list manipulations into helpers (diff) | |
| download | linux-97500a4a54876d3d6d2d1b8419223eb4e69b32d8.tar.xz linux-97500a4a54876d3d6d2d1b8419223eb4e69b32d8.zip | |
mm: maintain randomization of page free lists
When freeing a page with an order >= shuffle_page_order randomly select
the front or back of the list for insertion.
While the mm tries to defragment physical pages into huge pages this can
tend to make the page allocator more predictable over time. Inject the
front-back randomness to preserve the initial randomness established by
shuffle_free_memory() when the kernel was booted.
The overhead of this manipulation is constrained by only being applied
for MAX_ORDER sized pages by default.
[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/154899812788.3165233.9066631950746578517.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Keith Busch <keith.busch@intel.com>
Cc: Robert Elliott <elliott@hpe.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/shuffle.h')
| -rw-r--r-- | mm/shuffle.h | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/mm/shuffle.h b/mm/shuffle.h index 644c8ee97b9e..777a257a0d2f 100644 --- a/mm/shuffle.h +++ b/mm/shuffle.h @@ -36,6 +36,13 @@ static inline void shuffle_zone(struct zone *z) return; __shuffle_zone(z); } + +static inline bool is_shuffle_order(int order) +{ + if (!static_branch_unlikely(&page_alloc_shuffle_key)) + return false; + return order >= SHUFFLE_ORDER; +} #else static inline void shuffle_free_memory(pg_data_t *pgdat) { @@ -48,5 +55,10 @@ static inline void shuffle_zone(struct zone *z) static inline void page_alloc_shuffle(enum mm_shuffle_ctl ctl) { } + +static inline bool is_shuffle_order(int order) +{ + return false; +} #endif #endif /* _MM_SHUFFLE_H */ |