On Wed, 24 Feb 2021 at 16:54, Peter Zijlstra <pet...@infradead.org> wrote: > > On Wed, Feb 24, 2021 at 02:30:00PM +0100, Vincent Guittot wrote: > > Joel reported long preempt and irq off sequence in newidle_balance because > > of a large number of CPU cgroups in use and having to be updated. This > > patchset moves the update outside newidle_imblance. This enables to early > > abort during the updates in case of pending irq as an example. > > > > Instead of kicking a normal ILB that will wakes up CPU which is already > > idle, patch 6 triggers the update of statistics in the idle thread of > > the CPU before selecting and entering an idle state. > > I'm confused... update_blocked_averages(), which calls > __update_blocked_fair(), which is the one doing the cgroup iteration > thing, runs with rq->lock held, and thus will have IRQs disabled any > which way around we turn this thing. > > Or is the problem that we called nohz_idle_balance(), which does > update_nohz_stats() -> update_blocked_averages() for evey NOHZ cpu from > newidle balance, such that we get NR_NOHZ_CPUS * NR_CGROUPS IRQ latency? > Which is now reduced to just NR_CGROUPS ?
Yes we can now abort between each cpu update