[LTP] [PATCH v4 4/5] controllers/memcg: increase memory limit in subgroup charge

[Richard Palethorpe]

Hello Krzysztof,

Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com> writes:

> The memcg_subgroup_charge was failing on kernel v5.8 in around 10% cases
> with:
>
>     memcg_subgroup_charge 1 TINFO: Running memcg_process --mmap-anon -s 135168
>     memcg_subgroup_charge 1 TINFO: Warming up pid: 19289
>     memcg_subgroup_charge 1 TINFO: Process is still here after warm up: 19289
>     memcg_subgroup_charge 1 TFAIL: rss is 0, 135168 expected
>     memcg_subgroup_charge 1 TPASS: rss is 0 as expected
>
> In dmesg one could see that OOM killer killed the process even though
> group memory limit was matching the usage:
>
>     memcg_process invoked oom-killer: gfp_mask=0xcc0(GFP_KERNEL), order=0, oom_score_adj=0
>     CPU: 4 PID: 19289 Comm: memcg_process Not tainted 5.8.0-1031-oracle #32~20.04.2-Ubuntu
>     Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.4.1 12/03/2020
>     ...
>     memory: usage 132kB, limit 132kB, failcnt 9
>     memory+swap: usage 132kB, limit 9007199254740988kB, failcnt 0
>     kmem: usage 4kB, limit 9007199254740988kB, failcnt 0
>     ...
>     Tasks state (memory values in pages):
>     [  pid  ]   uid  tgid total_vm      rss pgtables_bytes swapents oom_score_adj name
>     [  19289]     0 19289      669      389    40960        0             0 memcg_process
>     oom-kill:constraint=CONSTRAINT_MEMCG,nodemask=(null),cpuset=/,mems_allowed=0,oom_memcg=/ltp_19257,task_memcg=/ltp_19257,task=memcg_process,pid=19289,uid=0
>     Memory cgroup out of memory: Killed process 19289 (memcg_process) total-vm:2676kB, anon-rss:84kB, file-rss:1468kB, shmem-rss:4kB, UID:0 pgtables:40kB oom_score_adj:0
>     oom_reaper: reaped process 19289 (memcg_process), now anon-rss:0kB, file-rss:0kB, shmem-rss:4kB
>
> It seems actual kernel memory usage by a given group depends on number
> of CPUs, where at least one page is allocated per-cpu beside regular
> (expected) allocation.  Fix the test on machines with more CPUs by
> including this per-CPU memory in group limits, plus some slack of 4
> PAGES.  Increase also memory allocation from 32 to 64 pages to be more
> distinctive from kernel per-CPU memory.

Actually I think it is 66 pages? Because PAGESIZES=pagesize*33.

>
> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
> ---
>  .../memcg/functional/memcg_subgroup_charge.sh | 33 ++++++++++++++-----
>  1 file changed, 25 insertions(+), 8 deletions(-)
>
> diff --git a/testcases/kernel/controllers/memcg/functional/memcg_subgroup_charge.sh b/testcases/kernel/controllers/memcg/functional/memcg_subgroup_charge.sh
> index 9b23177a4dc5..0d2b235aff7c 100755
> --- a/testcases/kernel/controllers/memcg/functional/memcg_subgroup_charge.sh
> +++ b/testcases/kernel/controllers/memcg/functional/memcg_subgroup_charge.sh
> @@ -14,16 +14,33 @@ TST_CNT=3
>  
>  . memcg_lib.sh
>  
> +# Allocate memory bigger than per-cpu kernel memory
> +MEM_TO_ALLOC=$((PAGESIZES * 2))
> +

-- 
Thank you,
Richard.