From mboxrd@z Thu Jan  1 00:00:00 1970
From: Michal =?iso-8859-1?Q?Koutn=FD?= <mkoutny@suse.com>
Subject: Re: [PATCH 0/7] introduce cpu.headroom knob to cpu controller
Date: Tue, 21 May 2019 15:47:30 +0200
Message-ID: <20190521134730.GA12346@blackbody.suse.cz>
References: <20190408214539.2705660-1-songliubraving@fb.com>
 <20190410115907.GE19434@e105550-lin.cambridge.arm.com>
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To: Song Liu <songliubraving@fb.com>
Cc: Morten Rasmussen <morten.rasmussen@arm.com>, Kernel Team <Kernel-team@fb.com>, "peterz@infradead.org" <peterz@infradead.org>, "vincent.guittot@linaro.org" <vincent.guittot@linaro.org>, "tglx@linutronix.de" <tglx@linutronix.de>, "mingo@redhat.com" <mingo@redhat.com>, "cgroups@vger.kernel.org" <cgroups@vger.kernel.org>, linux-kernel <linux-kernel@vger.kernel.org>


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Hello Song.

On Wed, Apr 10, 2019 at 07:43:35PM +0000, Song Liu <songliubraving@fb.com> =
wrote:
> The load level above is measured as requests-per-second.=20
>=20
> When there is no side workload, the system has about 45% busy CPU with=20
> load level of 1.0; and about 75% busy CPU at load level of 1.5.=20
>=20
> The saturation starts before the system hitting 100% utilization. This is
> true for many different resources: ALUs in SMT systems, cache lines,=20
> memory bandwidths, etc.=20
I have read through the thread continuation and it appears to me there
is some misunderstanding on the latency metric (scheduler latency <=3D
your latency <=3D request wall time?).

Could you please describe how is the latency that you report defined and
measured?

Thanks,
Michal


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