From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ingo Molnar <mingo@elte.hu>
Subject: Re: [patch] rt: sysprof hrtimer fix
Date: Fri, 13 Feb 2009 13:49:28 +0100
Message-ID: <20090213124928.GC5483@elte.hu>
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Cc: Thomas Gleixner <tglx@linutronix.de>,
	Thomas Gleixner <tglx@tglx.de>,
	LKML <linux-kernel@vger.kernel.org>,
	rt-users <linux-rt-users@vger.kernel.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Carsten Emde <ce@ceag.ch>, Clark Williams <williams@redhat.com>
To: Frederic Weisbecker <fweisbec@gmail.com>
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* Frederic Weisbecker <fweisbec@gmail.com> wrote:

> So, just a thing.
> -rt make the hrtimer's timers running on softirq context because the hrtimer_interrupt
> doesn't run as a threaded interrupt, and then it is not preemptible right?
> 
> In that case, sysprof will continue to run in hardirq context, as before, and
> it will considerably increase the latency. And that matters here.
> So I think it is important to put it on the reminder:

hm, not sure. Do you know it numerically how much worst-case overhead it
induces?

	Ingo