Re: [LKP] Re: [mm/memcg] bd0b230fe1: will-it-scale.per_process_ops -22.7% regression

Xing Zhengjun
2020-11-04T01:20:12Z

On 11/2/2020 6:02 PM, Michal Hocko wrote:
> On Mon 02-11-20 17:53:14, Rong Chen wrote:
>>
>>
>> On 11/2/20 5:27 PM, Michal Hocko wrote:
>>> On Mon 02-11-20 17:15:43, kernel test robot wrote:
>>>> Greeting,
>>>>
>>>> FYI, we noticed a -22.7% regression of will-it-scale.per_process_ops due to commit:
>>>>
>>>>
>>>> commit: bd0b230fe14554bfffbae54e19038716f96f5a41 ("mm/memcg: unify swap and memsw page counters")
>>>> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
>>> I really fail to see how this can be anything else than a data structure
>>> layout change. There is one counter less.
>>>
>>> btw. are cgroups configured at all? What would be the configuration?
>>
>> Hi Michal,
>>
>> We used the default configure of cgroups, not sure what configuration you
>> want,
>> could you give me more details? and here is the cgroup info of will-it-scale
>> process:
>>
>> $ cat /proc/3042/cgroup
>> 12:hugetlb:/
>> 11:memory:/system.slice/lkp-bootstrap.service
>
> OK, this means that memory controler is enabled and in use. Btw. do you
> get the original performance if you add one phony page_counter after the
> union?
>
I add one phony page_counter after the union and re-test, the regression
reduced to -1.2%. It looks like the regression caused by the data
structure layout change.

=========================================================================================
tbox_group/testcase/rootfs/kconfig/compiler/nr_task/mode/test/cpufreq_governor/ucode/debug-setup:

lkp-hsw-4ex1/will-it-scale/debian-10.4-x86_64-20200603.cgz/x86_64-rhel-8.3/gcc-9/50%/process/page_fault2/performance/0x16/test1

commit:
8d387a5f172f26ff8c76096d5876b881dec6b7ce
bd0b230fe14554bfffbae54e19038716f96f5a41
b3233916ab0a883e1117397e28b723bd0e4ac1eb (debug patch add one phony
page_counter after the union)

8d387a5f172f26ff bd0b230fe14554bfffbae54e190 b3233916ab0a883e1117397e28b
---------------- --------------------------- ---------------------------
%stddev %change %stddev %change %stddev
\ | \ | \
187632 -22.8% 144931 -1.2% 185391
will-it-scale.per_process_ops
13509525 -22.8% 10435073 -1.2% 13348181
will-it-scale.workload

--
Zhengjun Xing