Missed lists earlier :(

On 7 January 2014 20:31, Viresh Kumar viresh.kumar@linaro.org wrote:

Hi Kevin/Frederic,

In my traces I see a guaranteed interrupt on the isolated core, which is running under NO_HZ_FULL mode and is running a single thread "stress", after ~90 seconds.

When I look into the traces I see we get only two events:

• irq-handler-entry
• irq-handler-exit

And no more detail is available in the traces, system again goes to no interruption mode for next 90 seconds.

I hope this is because the timers we have queued for long enough times are getting overflowed? I tried to enable cpusets and then see which timers are active on CPU1 from /proc/timer_list and that gave me:

tick_sched_timer and it_real_fn. These are probably queued for long enough times, around 450 seconds and 2000 seconds.

So, my question is: Why are these getting queued? And how can I get rid of those for my case, where I want zero interruption on isolated core, as that would be running a userspace thread to handle data plane packets.

Another thing I tried out recently was to make my single threaded task "stress" a real time task with priority 99 (along with cpusets). But it seems there are more than one thread getting on that CPU and so tick occurs immediately.

I tried to call "stress" with help of chrt.

-- viresh