[LTP] [PATCH] memcontrol03: Account for process size in cgroup allocation

[Martin Doucha]

The first trunk_G allocation has 2MB safety margin to avoid triggering
OOM killer. However, on systems with 64K pagesize, this may not be enough.
Account for process size as reported by cgroup memory stats before
allocating memory in child processes.

Signed-off-by: Martin Doucha <mdoucha@suse.cz>
---
 .../kernel/controllers/memcg/memcontrol03.c   | 20 +++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/testcases/kernel/controllers/memcg/memcontrol03.c b/testcases/kernel/controllers/memcg/memcontrol03.c
index b5bbb9954..d2e489ad6 100644
--- a/testcases/kernel/controllers/memcg/memcontrol03.c
+++ b/testcases/kernel/controllers/memcg/memcontrol03.c
@@ -94,17 +94,23 @@ static void cleanup_sub_groups(void)
 }
 
 static void alloc_anon_in_child(const struct tst_cg_group *const cg,
-				const size_t size, const int expect_oom)
+	size_t size, const int expect_oom)
 {
 	int status;
 	const pid_t pid = SAFE_FORK();
+	size_t cgmem;
 
 	if (!pid) {
 		SAFE_CG_PRINTF(cg, "cgroup.procs", "%d", getpid());
+		SAFE_CG_SCANF(cg, "memory.current", "%zu", &cgmem);
+		size = size > cgmem ? size - cgmem : 0;
 
 		tst_res(TINFO, "Child %d in %s: Allocating anon: %"PRIdPTR,
 		getpid(), tst_cg_group_name(cg), size);
-		alloc_anon(size);
+
+		if (size)
+			alloc_anon(size);
+
 		exit(0);
 	}
 
@@ -128,9 +134,10 @@ static void alloc_anon_in_child(const struct tst_cg_group *const cg,
 }
 
 static void alloc_pagecache_in_child(const struct tst_cg_group *const cg,
-				     const size_t size)
+	size_t size)
 {
 	const pid_t pid = SAFE_FORK();
+	size_t cgmem;
 
 	if (pid) {
 		TST_CHECKPOINT_WAIT(CHILD_IDLE);
@@ -138,10 +145,15 @@ static void alloc_pagecache_in_child(const struct tst_cg_group *const cg,
 	}
 
 	SAFE_CG_PRINTF(cg, "cgroup.procs", "%d", getpid());
+	SAFE_CG_SCANF(cg, "memory.current", "%zu", &cgmem);
+	size = size > cgmem ? size - cgmem : 0;
 
 	tst_res(TINFO, "Child %d in %s: Allocating pagecache: %"PRIdPTR,
 		getpid(), tst_cg_group_name(cg), size);
-	alloc_pagecache(fd, size);
+
+	if (size)
+		alloc_pagecache(fd, size);
+
 	SAFE_FSYNC(fd);
 
 	TST_CHECKPOINT_WAKE(CHILD_IDLE);
-- 
2.49.0