+ mm-vmalloc-use-rb_tree-instead-of-list-for-vread-lookups.patch added to -mm tree

+ mm-vmalloc-use-rb_tree-instead-of-list-for-vread-lookups.patch added to -mm tree

[akpm]

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@delphix.com>
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@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>
---

 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@delphix.com are

mm-vmalloc-use-rb_tree-instead-of-list-for-vread-lookups.patch