Re: [PATCH] selftest/mm: Make hugetlb_reparenting_test tolerant to async reparenting

On 4/7/25 2:12 PM, Li Wang wrote:

In cgroup v2, memory and hugetlb usage reparenting is asynchronous. This can cause test flakiness when immediately asserting usage after deleting a child cgroup. To address this, add a helper function `assert_with_retry()` that checks usage values with a timeout-based retry. This improves test stability without relying on fixed sleep delays.

Also bump up the tolerance size to 7MB.

To avoid False Positives: ... # Assert memory charged correctly for child only use. # actual a = 11 MB # expected a = 0 MB # fail # cleanup # [FAIL] not ok 11 hugetlb_reparenting_test.sh -cgroup-v2 # exit=1 # 0 # SUMMARY: PASS=10 SKIP=0 FAIL=1

I was also seeing this failure. I have tested this patch on my powerPC setup and it is passing now.

./hugetlb_reparenting_test.sh -cgroup-v2 cleanup

Test charge, rmdir, uncharge mkdir write Writing to this path: /mnt/huge/test Writing this size: 52428800 Populating. Not writing to memory. Using method=0 Shared mapping. RESERVE mapping. Allocating using HUGETLBFS.

rmdir uncharge cleanup done

Test child only hugetlb usage setup write Writing to this path: /mnt/huge/test2 Writing this size: 52428800 Populating. Not writing to memory. Using method=0 Shared mapping. RESERVE mapping. Allocating using HUGETLBFS.

Assert memory charged correctly for child only use. actual = 10 MB expected = 0 MB cleanup

Feel free to add Tested-by Donet Tom donettom@linux.ibm.com

Signed-off-by: Li Wang liwang@redhat.com Cc: Waiman Long longman@redhat.com Cc: Anshuman Khandual anshuman.khandual@arm.com Cc: Dev Jain dev.jain@arm.com Cc: Kirill A. Shuemov kirill.shutemov@linux.intel.com Cc: Shuah Khan shuah@kernel.org

---

.../selftests/mm/hugetlb_reparenting_test.sh | 96 ++++++++----------- 1 file changed, 41 insertions(+), 55 deletions(-)

diff --git a/tools/testing/selftests/mm/hugetlb_reparenting_test.sh b/tools/testing/selftests/mm/hugetlb_reparenting_test.sh index 11f9bbe7dc22..1c172c6999f4 100755 --- a/tools/testing/selftests/mm/hugetlb_reparenting_test.sh +++ b/tools/testing/selftests/mm/hugetlb_reparenting_test.sh @@ -36,7 +36,7 @@ else do_umount=1 fi fi -MNT='/mnt/huge/' +MNT='/mnt/huge' function get_machine_hugepage_size() { hpz=$(grep -i hugepagesize /proc/meminfo) @@ -60,6 +60,41 @@ function cleanup() { set -e } +function assert_with_retry() {

• local actual_path="$1"
• local expected="$2"
• local tolerance=$((7 * 1024 * 1024))
• local timeout=20
• local interval=1
• local start_time
• local now
• local elapsed
• local actual
• start_time=$(date +%s)
• while true; do
• actual="$(cat "$actual_path")"
• if [[ $actual -ge $(($expected - $tolerance)) ]] &&

•    [[ $actual -le $(($expected + $tolerance)) ]]; then
  

•  return 0
  

• fi
• now=$(date +%s)
• elapsed=$((now - start_time))
• if [[ $elapsed -ge $timeout ]]; then

•  echo "actual = $((${actual%% *} / 1024 / 1024)) MB"
  

•  echo "expected = $((${expected%% *} / 1024 / 1024)) MB"
  

•  cleanup
  

•  exit 1
  

• fi
• sleep $interval
• done

+}

• function assert_state() { local expected_a="$1" local expected_a_hugetlb="$2"

@@ -70,58 +105,13 @@ function assert_state() { expected_b="$3" expected_b_hugetlb="$4" fi

• local tolerance=$((5 * 1024 * 1024))
• local actual_a
• actual_a="$(cat "$CGROUP_ROOT"/a/memory.$usage_file)"
• if [[ $actual_a -lt $(($expected_a - $tolerance)) ]] ||
• [[ $actual_a -gt $(($expected_a + $tolerance)) ]]; then
• echo actual a = $((${actual_a%% *} / 1024 / 1024)) MB
• echo expected a = $((${expected_a%% *} / 1024 / 1024)) MB
• echo fail
• cleanup
• exit 1
• fi
• local actual_a_hugetlb
• actual_a_hugetlb="$(cat "$CGROUP_ROOT"/a/hugetlb.${MB}MB.$usage_file)"
• if [[ $actual_a_hugetlb -lt $(($expected_a_hugetlb - $tolerance)) ]] ||
• [[ $actual_a_hugetlb -gt $(($expected_a_hugetlb + $tolerance)) ]]; then
• echo actual a hugetlb = $((${actual_a_hugetlb%% *} / 1024 / 1024)) MB
• echo expected a hugetlb = $((${expected_a_hugetlb%% *} / 1024 / 1024)) MB
• echo fail
• cleanup
• exit 1
• fi
• if [[ -z "$expected_b" || -z "$expected_b_hugetlb" ]]; then
• return
• fi
• local actual_b
• actual_b="$(cat "$CGROUP_ROOT"/a/b/memory.$usage_file)"
• if [[ $actual_b -lt $(($expected_b - $tolerance)) ]] ||
• [[ $actual_b -gt $(($expected_b + $tolerance)) ]]; then
• echo actual b = $((${actual_b%% *} / 1024 / 1024)) MB
• echo expected b = $((${expected_b%% *} / 1024 / 1024)) MB
• echo fail
• cleanup
• exit 1
• fi

• local actual_b_hugetlb
• actual_b_hugetlb="$(cat "$CGROUP_ROOT"/a/b/hugetlb.${MB}MB.$usage_file)"
• if [[ $actual_b_hugetlb -lt $(($expected_b_hugetlb - $tolerance)) ]] ||
• [[ $actual_b_hugetlb -gt $(($expected_b_hugetlb + $tolerance)) ]]; then
• echo actual b hugetlb = $((${actual_b_hugetlb%% *} / 1024 / 1024)) MB
• echo expected b hugetlb = $((${expected_b_hugetlb%% *} / 1024 / 1024)) MB
• echo fail

• assert_with_retry "$CGROUP_ROOT/a/memory.$usage_file" "$expected_a"
• assert_with_retry "$CGROUP_ROOT/a/hugetlb.${MB}MB.$usage_file" "$expected_a_hugetlb"

• cleanup
• exit 1

• if [[ -n "$expected_b" && -n "$expected_b_hugetlb" ]]; then
• assert_with_retry "$CGROUP_ROOT/a/b/memory.$usage_file" "$expected_b"
• assert_with_retry "$CGROUP_ROOT/a/b/hugetlb.${MB}MB.$usage_file" "$expected_b_hugetlb" fi }

@@ -174,7 +164,6 @@ size=$((${MB} * 1024 * 1024 * 25)) # 50MB = 25 * 2MB hugepages. cleanup -echo echo echo Test charge, rmdir, uncharge setup @@ -195,7 +184,6 @@ cleanup echo done echo -echo if [[ ! $cgroup2 ]]; then echo "Test parent and child hugetlb usage" setup @@ -212,7 +200,6 @@ if [[ ! $cgroup2 ]]; then assert_state 0 $(($size * 2)) 0 $size rmdir "$CGROUP_ROOT"/a/b

• sleep 5 echo Assert memory reparent correctly. assert_state 0 $(($size * 2))

@@ -224,7 +211,6 @@ if [[ ! $cgroup2 ]]; then cleanup fi -echo echo echo "Test child only hugetlb usage" echo setup