Re: [PATCH 4/4] selftests: memcg: Remove protection from top level memcg

On Fri, 13 May 2022 11:59:56 -0700 Roman Gushchin [off-list ref] wrote:

On Fri, May 13, 2022 at 07:18:11PM +0200, Michal Koutny wrote:

quoted

The reclaim is triggered by memory limit in a subtree, therefore the
testcase does not need configured protection against external reclaim.

Also, correct/deduplicate respective comments

Signed-off-by: Michal Koutný <mkoutny-IBi9RG/b67k@public.gmane.org>
---
 tools/testing/selftests/cgroup/test_memcontrol.c | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/tools/testing/selftests/cgroup/test_memcontrol.c b/tools/testing/selftests/cgroup/test_memcontrol.c
index 9ffacf024bbd..9d370aafd799 100644
--- a/tools/testing/selftests/cgroup/test_memcontrol.c
+++ b/tools/testing/selftests/cgroup/test_memcontrol.c

@@ -247,7 +247,7 @@ static int cg_test_proc_killed(const char *cgroup)
 
 /*
  * First, this test creates the following hierarchy:
- * A       memory.min = 50M,  memory.max = 200M
+ * A       memory.min = 0,    memory.max = 200M
  * A/B     memory.min = 50M,  memory.current = 50M
  * A/B/C   memory.min = 75M,  memory.current = 50M
  * A/B/D   memory.min = 25M,  memory.current = 50M

@@ -257,7 +257,7 @@ static int cg_test_proc_killed(const char *cgroup)
  * Usages are pagecache, but the test keeps a running
  * process in every leaf cgroup.
  * Then it creates A/G and creates a significant
- * memory pressure in it.
+ * memory pressure in A.
  *
  * A/B    memory.current ~= 50M
  * A/B/C  memory.current ~= 29M

@@ -335,8 +335,6 @@ static int test_memcg_min(const char *root)
 			      (void *)(long)fd);
 	}
 
-	if (cg_write(parent[0], "memory.min", "50M"))
-		goto cleanup;
 	if (cg_write(parent[1], "memory.min", "50M"))
 		goto cleanup;
 	if (cg_write(children[0], "memory.min", "75M"))

@@ -404,8 +402,8 @@ static int test_memcg_min(const char *root)
 
 /*
  * First, this test creates the following hierarchy:
- * A       memory.low = 50M,  memory.max = 200M
- * A/B     memory.low = 50M,  memory.current = 50M
+ * A       memory.low = 0,    memory.max = 200M
+ * A/B     memory.low = 50M,  memory.current = ...

Can you, please, just remove "memory.current = ...", it's not
because obvious what "..." means here.

You mean this?

--- a/tools/testing/selftests/cgroup/test_memcontrol.c~selftests-memcg-remove-protection-from-top-level-memcg-fix
+++ a/tools/testing/selftests/cgroup/test_memcontrol.c

@@ -403,15 +403,14 @@ cleanup:
 /*
  * First, this test creates the following hierarchy:
  * A       memory.low = 0,    memory.max = 200M
- * A/B     memory.low = 50M,  memory.current = ...
+ * A/B     memory.low = 50M
  * A/B/C   memory.low = 75M,  memory.current = 50M
  * A/B/D   memory.low = 25M,  memory.current = 50M
  * A/B/E   memory.low = 0,    memory.current = 50M
  * A/B/F   memory.low = 500M, memory.current = 0
  *
  * Usages are pagecache.
- * Then it creates A/G an creates a significant
- * memory pressure in it.
+ * Then it creates A/G and creates significant memory pressure in it.
  *
  * Then it checks actual memory usages and expects that:
  * A/B    memory.current ~= 50M

_

(includes gratuitous comment cleanup)

I assume your comment in
https://lkml.kernel.org/r/Yn6pBPq+lAXm9NG8@carbon can be addressed in a
later patch.

I'm not sure what to amke of https://lkml.kernel.org/r/Yn6pWPodGPlz+D8G@carbon

Do we feel this series needs more work before merging it up?