The patch titled
Subject: mm/vmalloc: use rb_tree instead of list for vread() lookups
has been added to the -mm tree. Its filename is
mm-vmalloc-use-rb_tree-instead-of-list-for-vread-lookups.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-vmalloc-use-rb_tree-instead-of-list-for-vread-lookups.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-vmalloc-use-rb_tree-instead-of-list-for-vread-lookups.patch
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------------------------------------------------------
From: Serapheim Dimitropoulos <serapheim.dimitro@xxxxxxxxxxx>
Subject: 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@xxxxxxxxxxx
Signed-off-by: Serapheim Dimitropoulos <serapheim@xxxxxxxxxxx>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/vmalloc.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
--- a/mm/vmalloc.c~mm-vmalloc-use-rb_tree-instead-of-list-for-vread-lookups
+++ a/mm/vmalloc.c
@@ -2894,7 +2894,10 @@ long vread(char *buf, char *addr, unsign
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;
_
Patches currently in -mm which might be from serapheim.dimitro@xxxxxxxxxxx are
mm-vmalloc-use-rb_tree-instead-of-list-for-vread-lookups.patch
