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Subject[PATCH 1/1] selftests/vm: 8x compaction_test speedup
Date
This patch reduces the running time for compaction_test from about 27
sec, to 3.3 sec, which is about an 8x speedup.

These numbers are for an Intel x86_64 system with 32 GB of DRAM.

The compaction_test.c program was spending most of its time doing
mmap(), 1 MB at a time, on about 25 GB of memory.

Instead, do the mmaps 100 MB at a time. (Going past 100 MB doesn't make
things go much faster, because other parts of the program are using the
remaining time.)

Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
tools/testing/selftests/vm/compaction_test.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/vm/compaction_test.c b/tools/testing/selftests/vm/compaction_test.c
index bcec71250873..9b420140ba2b 100644
--- a/tools/testing/selftests/vm/compaction_test.c
+++ b/tools/testing/selftests/vm/compaction_test.c
@@ -18,7 +18,8 @@

#include "../kselftest.h"

-#define MAP_SIZE 1048576
+#define MAP_SIZE_MB 100
+#define MAP_SIZE (MAP_SIZE_MB * 1024 * 1024)

struct map_list {
void *map;
@@ -165,7 +166,7 @@ int main(int argc, char **argv)
void *map = NULL;
unsigned long mem_free = 0;
unsigned long hugepage_size = 0;
- unsigned long mem_fragmentable = 0;
+ long mem_fragmentable_MB = 0;

if (prereq() != 0) {
printf("Either the sysctl compact_unevictable_allowed is not\n"
@@ -190,9 +191,9 @@ int main(int argc, char **argv)
return -1;
}

- mem_fragmentable = mem_free * 0.8 / 1024;
+ mem_fragmentable_MB = mem_free * 0.8 / 1024;

- while (mem_fragmentable > 0) {
+ while (mem_fragmentable_MB > 0) {
map = mmap(NULL, MAP_SIZE, PROT_READ | PROT_WRITE,
MAP_ANONYMOUS | MAP_PRIVATE | MAP_LOCKED, -1, 0);
if (map == MAP_FAILED)
@@ -213,7 +214,7 @@ int main(int argc, char **argv)
for (i = 0; i < MAP_SIZE; i += page_size)
*(unsigned long *)(map + i) = (unsigned long)map + i;

- mem_fragmentable--;
+ mem_fragmentable_MB -= MAP_SIZE_MB;
}

for (entry = list; entry != NULL; entry = entry->next) {
--
2.28.0
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