[LTP] [PATCH v2 1/3] controllers/memcg: accept range of max_usage_in_bytes

[Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>]

Several Linux kernel versions report higher max_usage_in_bytes than
expected size of 1024 pages. For example v5.4, v5.8, v5.10
and 5.13.0-rc5:

    memcg_max_usage_in_bytes_test 1 TINFO: Test memory.max_usage_in_bytes
    memcg_max_usage_in_bytes_test 1 TINFO: Running memcg_process --mmap-anon -s 4194304
    memcg_max_usage_in_bytes_test 1 TINFO: Warming up pid: 1393215
    memcg_max_usage_in_bytes_test 1 TINFO: Process is still here after warm up: 1393215
    memcg_max_usage_in_bytes_test 1 TFAIL: memory.max_usage_in_bytes is 4325376, 4194304 expected

It seems that recent Linux kernel reports more memory used than
expected.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
---
 .../kernel/controllers/memcg/functional/memcg_lib.sh  | 11 +++++++++--
 .../memcg/functional/memcg_max_usage_in_bytes_test.sh |  6 +++++-
 2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/testcases/kernel/controllers/memcg/functional/memcg_lib.sh b/testcases/kernel/controllers/memcg/functional/memcg_lib.sh
index d9bb6d94324d..083ef376e120 100755
--- a/testcases/kernel/controllers/memcg/functional/memcg_lib.sh
+++ b/testcases/kernel/controllers/memcg/functional/memcg_lib.sh
@@ -140,7 +140,8 @@ shmmax_cleanup()
 
 # Check size in memcg
 # $1 - Item name
-# $2 - Expected size
+# $2 - Expected size lower bound
+# $3 - Expected size upper bound (optional)
 check_mem_stat()
 {
 	local item_size
@@ -151,7 +152,13 @@ check_mem_stat()
 		item_size=$(grep -w $1 memory.stat | cut -d " " -f 2)
 	fi
 
-	if [ "$2" = "$item_size" ]; then
+	if [ "$3" ]; then
+		if [ $item_size -ge $2 ] && [ $item_size -le $3 ]; then
+			tst_res TPASS "$1 is ${2}-${3} as expected"
+		else
+			tst_res TFAIL "$1 is $item_size, ${2}-${3} expected"
+		fi
+	elif [ "$2" = "$item_size" ]; then
 		tst_res TPASS "$1 is $2 as expected"
 	else
 		tst_res TFAIL "$1 is $item_size, $2 expected"
diff --git a/testcases/kernel/controllers/memcg/functional/memcg_max_usage_in_bytes_test.sh b/testcases/kernel/controllers/memcg/functional/memcg_max_usage_in_bytes_test.sh
index 14daa4651798..a940606cbd34 100755
--- a/testcases/kernel/controllers/memcg/functional/memcg_max_usage_in_bytes_test.sh
+++ b/testcases/kernel/controllers/memcg/functional/memcg_max_usage_in_bytes_test.sh
@@ -12,6 +12,10 @@ TST_CNT=4
 . memcg_lib.sh
 
 MEM_TO_ALLOC=$((PAGESIZE * 1024))
+# Recent Linux kernels (at least v5.4) started reporting memory usage of 32
+# pages higher than requested allocation. Cause is not known, so let's just be
+# flexible.
+MEM_EXPECTED_UPPER=$((MEM_TO_ALLOC + PAGESIZE * 32))
 MEM_LIMIT=$((MEM_TO_ALLOC * 2))
 
 # Run test cases which checks memory.[memsw.]max_usage_in_bytes after make
@@ -32,7 +36,7 @@ test_max_usage_in_bytes()
 	signal_memcg_process $MEM_TO_ALLOC
 	signal_memcg_process $MEM_TO_ALLOC
 
-	check_mem_stat $item $MEM_TO_ALLOC
+	check_mem_stat $item $MEM_TO_ALLOC $MEM_EXPECTED_UPPER
 
 	if [ $check_after_reset -eq 1 ]; then
 		echo 0 > $item
-- 
2.27.0