Re: [net] 4890b686f4: netperf.Throughput_Mbps -69.4% regression

[Feng Tang <feng.tang@intel.com>]

On Sun, Jul 03, 2022 at 03:55:31PM -0700, Roman Gushchin wrote:
> On Sun, Jul 03, 2022 at 06:43:53PM +0800, Feng Tang wrote:
> > Hi Shakeel,
> > 
> > On Fri, Jul 01, 2022 at 08:47:29AM -0700, Shakeel Butt wrote:
> > > On Mon, Jun 27, 2022 at 8:49 PM Feng Tang <feng.tang@intel.com> wrote:
> > > > I just tested it, it does perform better (the 4th is with your patch),
> > > > some perf-profile data is also listed.
> > > >
> > > >  7c80b038d23e1f4c 4890b686f4088c90432149bd6de 332b589c49656a45881bca4ecc0 e719635902654380b23ffce908d
> > > > ---------------- --------------------------- --------------------------- ---------------------------
> > > >      15722           -69.5%       4792           -40.8%       9300           -27.9%      11341        netperf.Throughput_Mbps
> > > >
> > > >       0.00            +0.3        0.26 ±  5%      +0.5        0.51            +1.3        1.27 ±  2%pp.self.__sk_mem_raise_allocated
> > > >       0.00            +0.3        0.32 ± 15%      +1.7        1.74 ±  2%      +0.4        0.40 ±  2%  pp.self.propagate_protected_usage
> > > >       0.00            +0.8        0.82 ±  7%      +0.9        0.90            +0.8        0.84        pp.self.__mod_memcg_state
> > > >       0.00            +1.2        1.24 ±  4%      +1.0        1.01            +1.4        1.44        pp.self.try_charge_memcg
> > > >       0.00            +2.1        2.06            +2.1        2.13            +2.1        2.11        pp.self.page_counter_uncharge
> > > >       0.00            +2.1        2.14 ±  4%      +2.7        2.71            +2.6        2.60 ±  2%  pp.self.page_counter_try_charge
> > > >       1.12 ±  4%      +3.1        4.24            +1.1        2.22            +1.4        2.51        pp.self.native_queued_spin_lock_slowpath
> > > >       0.28 ±  9%      +3.8        4.06 ±  4%      +0.2        0.48            +0.4        0.68        pp.self.sctp_eat_data
> > > >       0.00            +8.2        8.23            +0.8        0.83            +1.3        1.26        pp.self.__sk_mem_reduce_allocated
> > > >
> > > > And the size of 'mem_cgroup' is increased from 4224 Bytes to 4608.
> > > 
> > > Hi Feng, can you please try two more configurations? Take Eric's patch
> > > of adding ____cacheline_aligned_in_smp in page_counter and for first
> > > increase MEMCG_CHARGE_BATCH to 64 and for second increase it to 128.
> > > Basically batch increases combined with Eric's patch.
> > 
> > With increasing batch to 128, the regression could be reduced to -12.4%.
> 
> If we're going to bump it, I wonder if we should scale it dynamically depending
> on the size of the memory cgroup?
 
I think it makes sense, or also make it a configurable parameter? From 
the test reports of 0Day, these charging/counting play critical role
in performance (easy to see up to 60% performance effect). If user only
wants memcg for isolating things or doesn't care charging/stats, these
seem to be extra taxes.

For bumping to 64 or 128, universal improvement is expected with the
only concern of accuracy.

Thanks,
Feng

> Thanks!