The patch titled
Subject: tools/vm/page-types.c: avoid memset() in walk_pfn() when count == 1
has been added to the -mm tree. Its filename is
tools-vm-page-typesc-avoid-memset-in-walk_pfn-when-count-==-1.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/tools-vm-page-typesc-avoid-memset-in-walk_pfn-when-count-%3D%3D-1.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/tools-vm-page-typesc-avoid-memset-in-walk_pfn-when-count-%3D%3D-1.patch
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------------------------------------------------------
From: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Subject: tools/vm/page-types.c: avoid memset() in walk_pfn() when count == 1
I found that page-types is very slow and my testing shows many timeout
errors. Here's an example with a simple program allocating 1000 thps.
$ time ./page-types -p $(pgrep -f test_alloc)
...
real 0m17.201s
user 0m16.889s
sys 0m0.312s
Most of time is spent in memset(). Currently memset() clears over whole
buffer for every walk_pfn() call, which is inefficient when walk_pfn() is
called from walk_vma(), because in that case walk_pfn() is called for each
pfn. So this patch limits the zero initialization only for the first
element.
$ time ./page-types.patched -p $(pgrep -f test_alloc)
...
real 0m0.182s
user 0m0.046s
sys 0m0.135s
Fixes: 954e95584579 ("tools/vm/page-types.c: add memory cgroup dumping and filtering")
Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Suggested-by: Konstantin Khlebnikov <koct9i@xxxxxxxxx>
Cc: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
tools/vm/page-types.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff -puN tools/vm/page-types.c~tools-vm-page-typesc-avoid-memset-in-walk_pfn-when-count-==-1 tools/vm/page-types.c
--- a/tools/vm/page-types.c~tools-vm-page-typesc-avoid-memset-in-walk_pfn-when-count-==-1
+++ a/tools/vm/page-types.c
@@ -633,7 +633,15 @@ static void walk_pfn(unsigned long voffs
unsigned long pages;
unsigned long i;
- memset(cgi, 0, sizeof cgi);
+ /*
+ * kpagecgroup_read() reads only if kpagecgroup were opened, but
+ * /proc/kpagecgroup might even not exist, so it's better to fill
+ * them with zeros here.
+ */
+ if (count == 1)
+ cgi[0] = 0;
+ else
+ memset(cgi, 0, sizeof cgi);
while (count) {
batch = min_t(unsigned long, count, KPAGEFLAGS_BATCH);
_
Patches currently in -mm which might be from n-horiguchi@xxxxxxxxxxxxx are
mm-madvise-pass-return-code-of-memory_failure-to-userspace.patch
mm-madvise-update-comment-on-sys_madvise.patch
proc-kpageflags-return-kpf_buddy-for-tail-buddy-pages.patch
proc-kpageflags-return-kpf_slab-for-slab-tail-pages.patch
tools-vm-page-typesc-support-swap-entry.patch
tools-vm-page-typesc-avoid-memset-in-walk_pfn-when-count-==-1.patch
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