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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 /fs/proc/task_mmu.c
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 'fs/proc/task_mmu.c')
-rw-r--r--fs/proc/task_mmu.c42
1 files changed, 13 insertions, 29 deletions
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 5830b2e129ed..8a03759bda38 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -488,42 +488,16 @@ static void smaps_account(struct mem_size_stats *mss, struct page *page,
}
#ifdef CONFIG_SHMEM
-static unsigned long smaps_shmem_swap(struct vm_area_struct *vma,
- unsigned long addr)
-{
- struct page *page;
-
- page = find_get_entry(vma->vm_file->f_mapping,
- linear_page_index(vma, addr));
- if (!page)
- return 0;
-
- if (radix_tree_exceptional_entry(page))
- return PAGE_SIZE;
-
- page_cache_release(page);
- return 0;
-
-}
-
static int smaps_pte_hole(unsigned long addr, unsigned long end,
struct mm_walk *walk)
{
struct mem_size_stats *mss = walk->private;
- while (addr < end) {
- mss->swap += smaps_shmem_swap(walk->vma, addr);
- addr += PAGE_SIZE;
- }
+ mss->swap += shmem_partial_swap_usage(
+ walk->vma->vm_file->f_mapping, addr, end);
return 0;
}
-#else
-static unsigned long smaps_shmem_swap(struct vm_area_struct *vma,
- unsigned long addr)
-{
- return 0;
-}
#endif
static void smaps_pte_entry(pte_t *pte, unsigned long addr,
@@ -555,7 +529,17 @@ static void smaps_pte_entry(pte_t *pte, unsigned long addr,
page = migration_entry_to_page(swpent);
} else if (unlikely(IS_ENABLED(CONFIG_SHMEM) && mss->check_shmem_swap
&& pte_none(*pte))) {
- mss->swap += smaps_shmem_swap(vma, addr);
+ page = find_get_entry(vma->vm_file->f_mapping,
+ linear_page_index(vma, addr));
+ if (!page)
+ return;
+
+ if (radix_tree_exceptional_entry(page))
+ mss->swap += PAGE_SIZE;
+ else
+ page_cache_release(page);
+
+ return;
}
if (!page)