On Thu, 16 Jan 2014, Viresh Kumar wrote:
On 15 January 2014 22:47, Frederic Weisbecker fweisbec@gmail.com wrote:
Are you sure about that? NO_HZ_FULL shouldn't touch much hrtimers. Those are independant from the tick.
Although some of them seem to rely on the softirq, but that seem to concern the tick hrtimer only.
To make it clear I was talking about the hrtimer used by tick_sched_timer. I have crossed checked which timers are active on isolated CPU from /proc/timer_list and it gave on tick_sched_timer's hrtimer.
In the attached trace (dft.txt), see these locations:
- Line 252: Time 302.573881: we scheduled the hrtimer for 300 seconds
ahead of current time.
- Line 254, 258, 262, 330, 334: We got interruptions continuously after
~90 seconds and this looked to be a case of timer's counter overflow. Isn't it? (I have removed some lines towards the end of this file to make it shorter, though dft.dat is untouched)
Just do the math.
max reload value / timer freq = max time span
So:
0x7fffffff / 24MHz = 89.478485 sec
Nothing to do here except to get rid of the requirement to arm the timer at all.
Thanks,
tglx