linux-kernel - Trouble with full nohz and lttng

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Message-ID: <CA+xJJ18xR+j6cf+nD_VUwXS3BJta_dZMWs+ih5CMB_5LN=Q8VA@mail.gmail.com>
Date:	Mon, 15 Apr 2013 15:57:00 +0200
From:	Mats Liljegren <mats.liljegren@...a.com>
To:	linux-kernel@...r.kernel.org,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Trouble with full nohz and lttng

When I use lttng, I keep getting ticks. Without lttng, no ticks. It's
the same application I run, the same way. The only difference is
whether lttng logging has been started or not.

The trace says "sched" as reason for not disabled ticks. Using "top" I
can't see any extra process/thread being created while my application
runs, my application gets 99-101% of the CPU. There are a couple of
kworker threads (3), a migration thread and a ksoftirq thread on the
same CPU as my application, though "top" gives no indication that they
do any execution.

Is this a known limitation of lttng, or is there something else going on here?

/Mats
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