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authorVlastimil Babka <vbabka@suse.cz>2016-01-15 02:19:23 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2016-01-15 03:00:49 +0300
commit48131e03ca4ed71d73fbe55c311a258c6fa2a090 (patch)
tree2957b6c97152f31bd97e0943f36ab03ea49b6a19 /include/linux/shmem_fs.h
parent6a15a37097c7e02390bb08d83dac433c9f10144f (diff)
downloadlinux-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/linux/shmem_fs.h')
-rw-r--r--include/linux/shmem_fs.h2
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)