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| author | Vlastimil Babka <vbabka@suse.cz> | 2016-01-15 02:19:23 +0300 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2016-01-15 03:00:49 +0300 |
| commit | 48131e03ca4ed71d73fbe55c311a258c6fa2a090 (patch) | |
| tree | 2957b6c97152f31bd97e0943f36ab03ea49b6a19 /include | |
| parent | 6a15a37097c7e02390bb08d83dac433c9f10144f (diff) | |
| download | linux-48131e03ca4ed71d73fbe55c311a258c6fa2a090.tar.xz | |
mm, proc: reduce cost of /proc/pid/smaps for unpopulated shmem mappings
Following the previous patch, further reduction of /proc/pid/smaps cost
is possible for private writable shmem mappings with unpopulated areas
where the page walk invokes the .pte_hole function. We can use radix
tree iterator for each such area instead of calling find_get_entry() in
a loop. This is possible at the extra maintenance cost of introducing
another shmem function shmem_partial_swap_usage().
To demonstrate the diference, I have measured this on a process that
creates a private writable 2GB mapping of a partially swapped out
/dev/shm/file (which cannot employ the optimizations from the prvious
patch) and doesn't populate it at all. I time how long does it take to
cat /proc/pid/smaps of this process 100 times.
Before this patch:
real 0m3.831s
user 0m0.180s
sys 0m3.212s
After this patch:
real 0m1.176s
user 0m0.180s
sys 0m0.684s
The time is similar to the case where a radix tree iterator is employed
on the whole mapping.
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jerome Marchand <jmarchan@redhat.com>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/shmem_fs.h | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h index bd58be5e7a2a..a43f41cb3c43 100644 --- a/include/linux/shmem_fs.h +++ b/include/linux/shmem_fs.h @@ -61,6 +61,8 @@ extern void shmem_truncate_range(struct inode *inode, loff_t start, loff_t end); extern int shmem_unuse(swp_entry_t entry, struct page *page); extern unsigned long shmem_swap_usage(struct vm_area_struct *vma); +extern unsigned long shmem_partial_swap_usage(struct address_space *mapping, + pgoff_t start, pgoff_t end); static inline struct page *shmem_read_mapping_page( struct address_space *mapping, pgoff_t index) |