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From: "Ahmed S. Darwish" <a.darwish@linutronix.de>
To: Michel Macena Oliveira <michel@austral-dynamics.com>
Cc: linux-rt-users@vger.kernel.org
Subject: Re: PREEMPT_RT benchmark
Date: Thu, 11 Mar 2021 13:58:21 +0100	[thread overview]
Message-ID: <YEoT7Wvk8V1cbHng@lx-t490> (raw)
In-Reply-To: <CAKkbJ-ypaPZ5JKpXD+PykvO6oYzxEUdxXY2RbVJKWdGY3ALuLg@mail.gmail.com>

On Wed, Mar 10, 2021 at 05:07:47PM -0300, Michel Macena Oliveira wrote:
>
> I'm currently developing a time benchmark application where I want
> to measure a real time thread latency. My application is based on
> Cyclictest from
> the rt-tests suit.
...
>
> I programmed in such way that it would be equivalent to Cyclict test
>
...
>
> At least that's what I expected, but my latencies are much bigger than
> Cyclictest ones.
>

I don't know the nature of the "time benchmark" application you are
writing.

Just a small hint that if you're doing any heavy OpenGL graphics within
that application, the latency can shoot up significantly. On some of our
Intel boxes, this can lead to an increase of 100-200 microseconds.

That's because since Intel Gen9+ GPUs, Intel shares the Last-Level Cache
(and thus also memory bandwidth) between the GPU and the CPU. This
benefits graphical applications, but hurts predicatbility significantly.

Good luck,

--
Ahmed S. Darwish
Linutronix GmbH

  parent reply	other threads:[~2021-03-11 12:59 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-10 20:07 PREEMPT_RT benchmark Michel Macena Oliveira
2021-03-11 12:27 ` Daniel Wagner
2021-03-11 13:38   ` John Ogness
2021-03-11 14:56   ` Michel Macena Oliveira
2021-03-11 16:17     ` Ahmed S. Darwish
2021-03-11 17:02       ` Michel Macena Oliveira
2021-03-11 17:56         ` Ahmed S. Darwish
2021-03-12 15:45           ` Michel Macena Oliveira
2021-03-11 12:58 ` Ahmed S. Darwish [this message]
2021-03-11 15:03   ` Michel Macena Oliveira
2021-03-11 16:01     ` Ahmed S. Darwish

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