Re: [PATCH v2 2/4] sched/idle: Don't handle polling idle as dynticks idle

[Frederic Weisbecker <frederic@kernel.org>]

Le Wed, Nov 11, 2026 at 12:43:48PM +0100, Marco Crivellari a écrit :
> TS_FLAG_INIDLE tells nohz whether the tick is managed by the idle loop or
> on IRQ exit. With idle=poll it is set while polling, but cpu_idle_poll()
> doesn't run the idle loop again on interrupts: a nohz_full kick or the
> expiry of a stopped tick isn't re-evaluated until something sets
> TIF_NEED_RESCHED. The tick is therefore restarted before polling, and on
> nohz_full CPUs it then keeps running after the wake-up and interrupts
> userspace.
> 
> Enter dynticks idle only on the cpuidle path, from cpuidle_idle_call(),
> and leave it before cpu_idle_poll(). While polling, the tick is then
> managed on IRQ exit as for a running task: on nohz_full CPUs it stays
> stopped if possible, and nothing is left to do on wake-up, so the task
> doesn't pay for a tick stop after waking up. On other CPUs, leaving
> dynticks idle restarts the tick as before.
> 
> tick_nohz_idle_enter() may now be called on each idle loop iteration and
> always runs with interrupts disabled; tick_nohz_idle_exit() may be called
> outside dynticks idle and with interrupts disabled.
> 
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Juri Lelli <juri.lelli@redhat.com>
> Cc: Vincent Guittot <vincent.guittot@linaro.org>
> Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: Ben Segall <bsegall@google.com>
> Cc: Mel Gorman <mgorman@suse.de>
> Cc: Valentin Schneider <vschneid@redhat.com>
> Cc: K Prateek Nayak <kprateek.nayak@amd.com>
> Cc: Paul E. McKenney <paulmck@kernel.org>
> Cc: Anna-Maria Behnsen <anna-maria@linutronix.de>
> Cc: Thomas Gleixner <tglx@kernel.org>
> Link: https://lore.kernel.org/all/aQiWfnnSzxsnwa2o@tpad/
> Suggested-by: Frederic Weisbecker <frederic@kernel.org>
> Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>

Reviewed-by: Frederic Weisbecker <frederic@kernel.org>

-- 
Frederic Weisbecker
SUSE Labs