test_percpu_basic() currently compares memory.current against only
memory.stat:percpu after creating 1000 child cgroups.
Observed failure:
#./test_kmem
ok 1 test_kmem_basic
ok 2 test_kmem_memcg_deletion
ok 3 test_kmem_proc_kpagecgroup
ok 4 test_kmem_kernel_stacks
ok 5 test_kmem_dead_cgroups
memory.current 11530240
percpu 8440000
not ok 6 test_percpu_basic
That assumption is too strict: child cgroup creation also allocates
slab-backed metadata, so memory.current is expected to be larger than
percpu alone. One visible path is:
cgroup_mkdir()
cgroup_create()
cgroup_addrm_file()
cgroup_add_file()
__kernfs_create_file()
__kernfs_new_node()
kmem_cache_zalloc()
These kernfs allocations are charged as slab and show up in
memory.stat:slab.
Update the check to compare memory.current against (percpu + slab)
within MAX_VMSTAT_ERROR, and print slab/delta in the failure message to
improve diagnostics.
Signed-off-by: Li Wang <[email protected]>
Cc: Waiman Long <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Shakeel Butt <[email protected]>
Cc: Tejun Heo <[email protected]>
Cc: Vlastimil Babka <[email protected]>
---
tools/testing/selftests/cgroup/test_kmem.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/tools/testing/selftests/cgroup/test_kmem.c
b/tools/testing/selftests/cgroup/test_kmem.c
index 249d79113067..4b5799698893 100644
--- a/tools/testing/selftests/cgroup/test_kmem.c
+++ b/tools/testing/selftests/cgroup/test_kmem.c
@@ -353,7 +353,7 @@ static int test_percpu_basic(const char *root)
{
int ret = KSFT_FAIL;
char *parent, *child;
- long current, percpu;
+ long current, percpu, slab;
int i;
parent = cg_name(root, "percpu_basic_test");
@@ -379,13 +379,14 @@ static int test_percpu_basic(const char *root)
current = cg_read_long(parent, "memory.current");
percpu = cg_read_key_long(parent, "memory.stat", "percpu ");
+ slab = cg_read_key_long(parent, "memory.stat", "slab ");
- if (current > 0 && percpu > 0 && labs(current - percpu) <
- MAX_VMSTAT_ERROR)
+ if (current > 0 && percpu > 0 && slab >= 0 &&
+ labs(current - (percpu + slab)) < MAX_VMSTAT_ERROR)
ret = KSFT_PASS;
else
- printf("memory.current %ld\npercpu %ld\n",
- current, percpu);
+ printf("memory.current %ld\npercpu %ld\nslab %ld\ndelta %ld\n",
+ current, percpu, slab, current - (percpu + slab));
cleanup_children:
for (i = 0; i < 1000; i++) {
--
2.53.0
