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authorSerapheim Dimitropoulos <serapheim.dimitro@delphix.com>2021-04-29 22:58:07 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2021-04-30 11:20:39 -0700
commitf608788cd2d6cae27d1a3d2253544ca76b353764 (patch)
tree645f0c8c6063d2e7fa4b2c545c1a41e37d65ff59 /mm
parent0f71d7e14c2129c5b99aec6961a55b331f9dbaf1 (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')
-rw-r--r--mm/vmalloc.c5
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;