Commit e12d0271 authored May 10, 2013 by Steven Rostedt Committed by Frederic Weisbecker Jun 20, 2013

nohz: Warn if the machine can not perform nohz_full



If the user configures NO_HZ_FULL and defines nohz_full=XXX on the
kernel command line, or enables NO_HZ_FULL_ALL, but nohz fails
due to the machine having a unstable clock, warn about it.

We do not want users thinking that they are getting the benefit
of nohz when their machine can not support it.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

parent 7d132055

kernel/time/tick-sched.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -178,6 +178,11 @@ static bool can_stop_full_tick(void)
		*/
		if (!sched_clock_stable) {
		trace_tick_stop(0, "unstable sched clock\n");
		/*
		* Don't allow the user to think they can get
		* full NO_HZ with this machine.
		*/
		WARN_ONCE(1, "NO_HZ FULL will not work with unstable sched clock");
		return false;
		}
		#endif