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From:   Valentin Schneider <valentin.schneider@arm.com>
To:     Oliver Sang <oliver.sang@intel.com>
Cc:     0day robot <lkp@intel.com>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        LKML <linux-kernel@vger.kernel.org>, lkp@lists.01.org,
        ying.huang@intel.com, feng.tang@intel.com, zhengjun.xing@intel.com,
        Lingutla Chandrasekhar <clingutla@codeaurora.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@kernel.org>,
        Morten Rasmussen <morten.rasmussen@arm.com>,
        Qais Yousef <qais.yousef@arm.com>,
        Quentin Perret <qperret@google.com>,
        Pavan Kondeti <pkondeti@codeaurora.org>,
        Rik van Riel <riel@surriel.com>, aubrey.li@linux.intel.com,
        yu.c.chen@intel.com
Subject: Re: [sched/fair]  38ac256d1c:  stress-ng.vm-segv.ops_per_sec -13.8% regression
In-Reply-To: <87wnsutzi9.mognet@arm.com>
References: <20210414052151.GB21236@xsang-OptiPlex-9020> <87im4on5u5.mognet@arm.com> <20210421032022.GA13430@xsang-OptiPlex-9020> <87bla8ue3e.mognet@arm.com> <20210422074742.GE31382@xsang-OptiPlex-9020> <87wnsutzi9.mognet@arm.com>
Date:   Thu, 22 Apr 2021 21:42:31 +0100
Message-ID: <87mttqt5jc.mognet@arm.com>
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On 22/04/21 10:55, Valentin Schneider wrote:
> I'll go find myself some other x86 box and dig into it;
> I'd rather not leave this hanging for too long.

So I found myself a dual-socket Xeon Gold 5120 @ 2.20GHz (64 CPUs) and
*there* I get a somewhat consistent ~-6% regression. As I'm suspecting
cacheline shenanigans, I also ran that with Peter's recent
kthread_is_per_cpu() change, and that brings it down to ~-3%

I'll leave it at here for today, but at least that's something I can work
with.