Re: [LTP] [PATCH 3/3] memcontrol04: Copy from kselftest

[Richard Palethorpe <rpalethorpe@suse.de>]

Hello Li,

Li Wang <liwang@redhat.com> writes:

> On Thu, Feb 10, 2022 at 2:23 PM Li Wang <liwang@redhat.com> wrote:
>
>  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'
>
> My apologies, the leaf_cg[E] does not have 50MB page cache
> allocating, that is the main reason with no memory reclaims happening.
> '500MB' low boundary obviously overcommitment, so leaf_cg[E] will
> get the part of parent’s protection proportional to its actual memory
> usage. However, it doesn't matter for this case, leaf_cg[E] can get
> no event grows as well. Because it has no memory consumption at all.

leaf_cg[F]'s memory.low == 0. So how can it have reclaim events where
memory.current < memory.low?

Testing on the upstream kernel there are no low events in F.

>
> The fix is still effective unless I misread something again:).
>
>  
>  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);

Note that I am just copying the original test. AFAICT the original did
not expect there to be low events in F.

>
>  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);

+1, thanks!

>
>  -- 
>  Regards,
>  Li Wang


-- 
Thank you,
Richard.

-- 
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