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Date:   Fri, 18 Oct 2019 10:38:06 +0200 (CEST)
From:   Thomas Gleixner <tglx@linutronix.de>
To:     David Miller <davem@davemloft.net>
cc:     Clark Williams <williams@redhat.com>,
        Sebastian Sewior <bigeasy@linutronix.de>, daniel@iogearbox.net,
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        Arnaldo Carvalho de Melo <acme@redhat.com>
Subject: Re: [PATCH] BPF: Disable on PREEMPT_RT
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On Thu, 17 Oct 2019, David Miller wrote:

> From: Clark Williams <williams@redhat.com>
> Date: Thu, 17 Oct 2019 21:49:17 -0500
> 
> > BPF programs cannot loop and are limited to 4096 instructions.
> 
> The limit was increased to 1 million not too long ago.

Assuming a instruction/cycle ratio of 1.0 and a CPU frequency of 2GHz,
that's 500us of preempt disabled time. Out of bounds by at least one order
of magntiude for a lot of RT scenarios.

Thanks,

	tglx