linux-kernel - Re: [PATCH] sched/rt: RT_RUNTIME

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Message-ID: <20161107133046.7e4458c1@gandalf.local.home>
Date:   Mon, 7 Nov 2016 13:30:46 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Clark Williams <williams@...hat.com>
Cc:     Daniel Bristot de Oliveira <bristot@...hat.com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Christoph Lameter <cl@...ux.com>,
        linux-rt-users <linux-rt-users@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] sched/rt: RT_RUNTIME_GREED sched feature

On Mon, 7 Nov 2016 12:22:21 -0600
Clark Williams <williams@...hat.com> wrote:

> I'm still reviewing the patch, but I have to wonder why bother with making it a scheduler feature?
> 
> The SCHED_FIFO definition allows a fifo thread to starve others
> because a fifo task will run until it yields. Throttling was added as
> a safety valve to allow starved SCHED_OTHER tasks to get some cpu
> time.  Adding this unconditionally gets us a safety valve for
> throttling a badly written fifo task, but allows the fifo task to
> continue to consume cpu cycles if it's not starving anyone. 
> 
> Or am I missing something that's blazingly obvious?

Or I say make it the default. If people want the old behavior, they can
modify SCHED_FEATURES to do so.

-- Steve