linux-kernel - Re: [net] 4890b686f4: netperf.Throughput

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Message-ID: <CALvZod71Fti8yLC08mdpDk-TLYJVyfVVauWSj1zk=BhN1-GPdA@mail.gmail.com>
Date:   Fri, 1 Jul 2022 08:47:29 -0700
From:   Shakeel Butt <shakeelb@...gle.com>
To:     Feng Tang <feng.tang@...el.com>
Cc:     Eric Dumazet <edumazet@...gle.com>, Linux MM <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Michal Hocko <mhocko@...nel.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Muchun Song <songmuchun@...edance.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Xin Long <lucien.xin@...il.com>,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        kernel test robot <oliver.sang@...el.com>,
        Soheil Hassas Yeganeh <soheil@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        network dev <netdev@...r.kernel.org>,
        linux-s390@...r.kernel.org, MPTCP Upstream <mptcp@...ts.linux.dev>,
        "linux-sctp @ vger . kernel . org" <linux-sctp@...r.kernel.org>,
        lkp@...ts.01.org, kbuild test robot <lkp@...el.com>,
        Huang Ying <ying.huang@...el.com>,
        Xing Zhengjun <zhengjun.xing@...ux.intel.com>,
        Yin Fengwei <fengwei.yin@...el.com>, Ying Xu <yinxu@...hat.com>
Subject: Re: [net] 4890b686f4: netperf.Throughput_Mbps -69.4% regression

On Mon, Jun 27, 2022 at 8:49 PM Feng Tang <feng.tang@...el.com> wrote:
>
> On Mon, Jun 27, 2022 at 06:25:59PM +0200, Eric Dumazet wrote:
> > On Mon, Jun 27, 2022 at 4:48 PM Feng Tang <feng.tang@...el.com> wrote:
> > >
> > > Yes, I also analyzed the perf-profile data, and made some layout changes
> > > which could recover the changes from 69% to 40%.
> > >
> > > 7c80b038d23e1f4c 4890b686f4088c90432149bd6de 332b589c49656a45881bca4ecc0
> > > ---------------- --------------------------- ---------------------------
> > >      15722           -69.5%       4792           -40.8%       9300        netperf.Throughput_Mbps
> > >
> >
> > I simply did the following and got much better results.
> >
> > But I am not sure if updates to ->usage are really needed that often...
> >
> >
> > diff --git a/include/linux/page_counter.h b/include/linux/page_counter.h
> > index 679591301994d316062f92b275efa2459a8349c9..e267be4ba849760117d9fd041e22c2a44658ab36
> > 100644
> > --- a/include/linux/page_counter.h
> > +++ b/include/linux/page_counter.h
> > @@ -3,12 +3,15 @@
> >  #define _LINUX_PAGE_COUNTER_H
> >
> >  #include <linux/atomic.h>
> > +#include <linux/cache.h>
> >  #include <linux/kernel.h>
> >  #include <asm/page.h>
> >
> >  struct page_counter {
> > -       atomic_long_t usage;
> > -       unsigned long min;
> > +       /* contended cache line. */
> > +       atomic_long_t usage ____cacheline_aligned_in_smp;
> > +
> > +       unsigned long min ____cacheline_aligned_in_smp;
> >         unsigned long low;
> >         unsigned long high;
> >         unsigned long max;
> > @@ -27,12 +30,6 @@ struct page_counter {
> >         unsigned long watermark;
> >         unsigned long failcnt;
> >
> > -       /*
> > -        * 'parent' is placed here to be far from 'usage' to reduce
> > -        * cache false sharing, as 'usage' is written mostly while
> > -        * parent is frequently read for cgroup's hierarchical
> > -        * counting nature.
> > -        */
> >         struct page_counter *parent;
> >  };
>
> 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.