On Wed, Feb 9, 2022 at 7:05 PM Li Wang <liwang@redhat.com> wrote:


> Btw, there are some TFAILs from my manual run.
> (I will look into that try to figure it out tomorrow)
>
> tst_test.c:1521: TINFO: Testing on ext4
> tst_test.c:996: TINFO: Formatting /dev/loop0 with ext4 opts='' extra
> opts=''
> mke2fs 1.46.5 (30-Dec-2021)
> tst_test.c:1452: TINFO: Timeout per run is 0h 05m 00s
> memcontrol04.c:118: TINFO: Child 242775 in leaf_C: Allocating pagecache:
> 52428800
> memcontrol04.c:118: TINFO: Child 242776 in leaf_D: Allocating pagecache:
> 52428800
> memcontrol04.c:118: TINFO: Child 242777 in leaf_F: Allocating pagecache:
> 52428800
> memcontrol04.c:99: TINFO: Child 242778 in trunk_G: Allocating anon:
> 155189248
> memcontrol04.c:170: TPASS: Expect: (A/B memory.current=54181888) ~=
> 52428800
> memcontrol04.c:176: TPASS: Expect: (A/B/C memory.current=30957568) ~=
> 34603008
> memcontrol04.c:178: TPASS: Expect: (A/B/D memory.current=22282240) ~=
> 17825792
> memcontrol04.c:180: TPASS: Expect: (A/B/E memory.current=0) ~= 0
> memcontrol04.c:99: TINFO: Child 242779 in trunk_G: Allocating anon:
> 174063616
> memcontrol04.c:193: TPASS: Expect: (oom events=0) == 0
> memcontrol04.c:196: TPASS: Expect: (low events=373) > 0
> memcontrol04.c:193: TPASS: Expect: (oom events=0) == 0
> memcontrol04.c:196: TPASS: Expect: (low events=373) > 0
> memcontrol04.c:193: TPASS: Expect: (oom events=0) == 0
> memcontrol04.c:198: TPASS: Expect: (low events=0) == 0
> memcontrol04.c:193: TPASS: Expect: (oom events=0) == 0
> memcontrol04.c:198: TFAIL: Expect: (low events=370) == 0
>

It looks like a logic issue here, as we do alloc_pagecache 50MB
respectively in the leaf_cg[C, D, E, F] and only the 'memory.low'
of leaf_cg[E] is large enough (500MB) to avoid triggering low event.
The rest cgroups should all have low events, that kernel behavior
is correct.

This failure should be fix with:

--- a/testcases/kernel/controllers/memcg/memcontrol04.c
+++ b/testcases/kernel/controllers/memcg/memcontrol04.c
@@ -192,7 +192,7 @@ static void test_memcg_low(void)

                TST_EXP_EXPR(oom == 0, "(oom events=%ld) == 0", oom);

-               if (i < E)
+               if (i != E)
                        TST_EXP_EXPR(low > 0, "(low events=%ld) > 0", low)
                else
                        TST_EXP_EXPR(low == 0, "(low events=%ld) == 0",
low);


And better to add "leaf_cg%d" print in the output:
(to show the events from which cgroup)

    TST_EXP_EXPR(oom == 0, "(leaf_cg%d: oom events=%ld) == 0", i, oom);

    if (i != E)
            TST_EXP_EXPR(low > 0, "(leaf_cg%d: low events=%ld) > 0", i,
 low)
    else
             TST_EXP_EXPR(low == 0, "(leaf_cg%d: low events=%ld) == 0", i,
low);

-- 
Regards,
Li Wang