[LTP] [PATCH] move_pages12: compacting memory before each test loop

[Li Wang]

These simple steps are added to prepare the system's memory state
for the test, aiming to increase the test's reliability and
consistency by starting from a clean and defragmented memory state.

To reduce accidental failures on small (1.5G) RAM system:

  7 tst_test.c:1558: TINFO: Timeout per run is 0h 21m 00s
  8 move_pages12.c:273: TINFO: Free RAM 1542656 kB
  9 move_pages12.c:289: TINFO: Increasing 16384kB hugepages pool on node 0 to 4
  10 move_pages12.c:299: TINFO: Increasing 16384kB hugepages pool on node 1 to 4
  11 move_pages12.c:216: TINFO: Allocating and freeing 4 hugepages on node 0
  12 move_pages12.c:216: TINFO: Allocating and freeing 4 hugepages on node 1
  13 move_pages12.c:207: TPASS: Bug not reproduced
  14 move_pages12.c:106: TFAIL: madvise failed: ENOMEM (12)
  ...<repeats 741 times>...
  756 move_pages12.c:207: TPASS: Bug not reproduced

Note:
  This is a single hugetlb test without invoking the hugetlb-lib of LTP,
  so we add the compacting memory/cache steps additionally.

Signed-off-by: Li Wang <liwang@redhat.com>
---
 testcases/kernel/syscalls/move_pages/move_pages12.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/testcases/kernel/syscalls/move_pages/move_pages12.c b/testcases/kernel/syscalls/move_pages/move_pages12.c
index fd7017d79..c387a326f 100644
--- a/testcases/kernel/syscalls/move_pages/move_pages12.c
+++ b/testcases/kernel/syscalls/move_pages/move_pages12.c
@@ -154,6 +154,9 @@ static void do_test(unsigned int n)
 	pid_t cpid = -1;
 	int status;
 
+	SAFE_FILE_PRINTF("/proc/sys/vm/drop_caches", "3");
+	SAFE_FILE_PRINTF("/proc/sys/vm/compact_memory", "1");
+
 	addr = SAFE_MMAP(NULL, tcases[n].tpages * hpsz, PROT_READ | PROT_WRITE,
 		MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB, -1, 0);
 
-- 
2.40.1