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

Michal Hocko
2020-11-04T08:15:50Z

On Wed 04-11-20 09:20:04, Xing Zhengjun wrote:
>
>
> 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.

Thanks for double checking. Could you try to cache align the
page_counter struct? If that helps then we should figure which counters
acks against each other by adding the alignement between the respective
counters.

> =========================================================================================
> 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

--
Michal Hocko
SUSE Labs