Re: EEVDF and NUMA balancing

Julia Lawall
2024-01-05T14:51:52Z

> Your system is calling the polling mode and not the default
> cpuidle_idle_call() ? This could explain why I don't see such problem
> on my system which doesn't have polling
>
> Are you forcing the use of polling mode ?
> If yes, could you check that this problem disappears without forcing
> polling mode ?

I expanded the code in do_idle to:

if (cpu_idle_force_poll) { c1++;
tick_nohz_idle_restart_tick();
cpu_idle_poll();
} else if (tick_check_broadcast_expired()) { c2++;
tick_nohz_idle_restart_tick();
cpu_idle_poll();
} else { c3++;
cpuidle_idle_call();
}

Later, I have:

trace_printk("force poll: %d: c1: %d, c2: %d, c3: %d\n",cpu_idle_force_poll, c1, c2, c3);
flush_smp_call_function_queue();
schedule_idle();

force poll, c1 and c2 are always 0, and c3 is always some non-zero value.
Sometimes small (often 1), and sometimes large (304 or 305).

So I don't think it's calling cpu_idle_poll().

x86 has TIF_POLLING_NRFLAG defined to be a non zero value, which I think
is sufficient to cause the issue.

julia