diff options
| author | Serapheim Dimitropoulos <serapheim.dimitro@delphix.com> | 2021-04-29 22:58:07 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2021-04-30 11:20:39 -0700 |
| commit | f608788cd2d6cae27d1a3d2253544ca76b353764 (patch) | |
| tree | 645f0c8c6063d2e7fa4b2c545c1a41e37d65ff59 /mm/vmalloc.c | |
| parent | 0f71d7e14c2129c5b99aec6961a55b331f9dbaf1 (diff) | |
mm/vmalloc: use rb_tree instead of list for vread() lookups
vread() has been linearly searching vmap_area_list for looking up vmalloc
areas to read from. These same areas are also tracked by a rb_tree
(vmap_area_root) which offers logarithmic lookup.
This patch modifies vread() to use the rb_tree structure instead of the
list and the speedup for heavy /proc/kcore readers can be pretty
significant. Below are the wall clock measurements of a Python
application that leverages the drgn debugging library to read and
interpret data read from /proc/kcore.
Before the patch:
-----
$ time sudo sdb -e 'dbuf | head 3000 | wc'
(unsigned long)3000
real 0m22.446s
user 0m2.321s
sys 0m20.690s
-----
With the patch:
-----
$ time sudo sdb -e 'dbuf | head 3000 | wc'
(unsigned long)3000
real 0m2.104s
user 0m2.043s
sys 0m0.921s
-----
Link: https://lkml.kernel.org/r/20210209190253.108763-1-serapheim@delphix.com
Signed-off-by: Serapheim Dimitropoulos <serapheim@delphix.com>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/vmalloc.c')
| -rw-r--r-- | mm/vmalloc.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 735b501ac412..8c20670e246d 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -2894,7 +2894,10 @@ long vread(char *buf, char *addr, unsigned long count) count = -(unsigned long) addr; spin_lock(&vmap_area_lock); - list_for_each_entry(va, &vmap_area_list, list) { + va = __find_vmap_area((unsigned long)addr); + if (!va) + goto finished; + list_for_each_entry_from(va, &vmap_area_list, list) { if (!count) break; |