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Date:   Tue, 31 Aug 2021 11:23:04 +0200
From:   Michal =?iso-8859-1?Q?Koutn=FD?= <mkoutny@suse.com>
To:     Feng Tang <feng.tang@intel.com>
Cc:     Johannes Weiner <hannes@cmpxchg.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        andi.kleen@intel.com, kernel test robot <oliver.sang@intel.com>,
        Roman Gushchin <guro@fb.com>, Michal Hocko <mhocko@suse.com>,
        Shakeel Butt <shakeelb@google.com>,
        Balbir Singh <bsingharora@gmail.com>,
        Tejun Heo <tj@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        LKML <linux-kernel@vger.kernel.org>, lkp@lists.01.org,
        kernel test robot <lkp@intel.com>,
        "Huang, Ying" <ying.huang@intel.com>,
        Zhengjun Xing <zhengjun.xing@linux.intel.com>
Subject: Re: [mm] 2d146aa3aa: vm-scalability.throughput -36.4% regression
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On Tue, Aug 31, 2021 at 02:30:36PM +0800, Feng Tang <feng.tang@intel.com> wrote:
> Yes, I tried many re-arrangement of the members of cgroup_subsys_state,
> and even close members of memcg, but there were no obvious changes.
> What can recover the regresion is adding 128 bytes padding in the css,
> no matter at the start, end or in the middle.

Do you mean the padding added outside the .cgroup--.refcnt members area
also restores the benchmark results? (Or you refer to paddings that move
.cgroup and .refcnt across a cacheline border ?) I'm asking to be sure
we have correct understanding of what members are contended (what's the
frequent writer).

Thanks,
Michal