[LTP] [PATCH v2] controllers/memcg: Add testcase for kmem_limit_in_bytes of memory cgroup

[Richard Palethorpe <rpalethorpe@suse.de>]

Hello,

zhaogongyi <zhaogongyi@huawei.com> writes:

> Hi Richard,
>
> That's right. I have a Misunderstanding of cgroup.procs. Actrually, we can write pid or tgid to cgroup.procs instead of pgid.
>
> I'll update the code as:
>
> 	SAFE_FILE_PRINTF(CGROUP_PROCS, "%d", getpid());
>
> BTW I find that the testcase run passed on my local system, it seems
> that tst_* will not trig memory allocation:

After a short search I found do_tty_write can return ENOMEM due to a
call to kmalloc with GFP_KERNEL.

As I said previously stderr can point to many things with different
write implementations. Some of these are likely to trigger memory
allocation. Please see my previous reply and suggestion.

Also please note the warning message in the kernel log when using
memory.kmem.limit_in_bytes.

>
> tst_test.c:1291: TINFO: Timeout per run is 0h 05m 00s
> memcg_kmem_limit_in_bytes.c:58: TPASS: fork fail as expected
> memcg_kmem_limit_in_bytes.c:73: TPASS: kmem alloc is controled by
> memory.kmem.limit_in_bytes
>
> Summary:
> passed   2
> failed   0
> broken   0
> skipped  0
> warnings 0
>
>
> Thanks very much!
>
> Best Regards,
> Gongyi
>
>> 
>> Hello,
>> 
>> zhaogongyi <zhaogongyi@huawei.com> writes:
>> 
>> > Hi Richard,
>> >
>> > Calling setpgid in this testcase is aim to make the task group be
>> controlled by memory.kmem.limit_in_bytes since we have set the pgid to
>> cgroup.procs.
>> >
>> 
>> Please see cgroup_procs_write_start in cgroup/cgroup.c. It calls
>> find_task_by_vpid which interprets pid as PIDTYPE_PID not PIDTYPE_PGID.
>> 
>> --
>> Thank you,
>> Richard.


-- 
Thank you,
Richard.