On Mon, Jan 29, 2018 at 07:31:07PM +0000, Valentin Schneider wrote: > But for load update via _nohz_idle_balance(), we iterate through all of the > nohz CPUS and unconditionally call update_blocked_averages(). This could be > avoided by remembering which CPUs have stale load before going idle. > Initially I thought that was what nohz.stats_state was for, but it isn't. > With Vincent's patches it's only ever set to either 0 or 1, but we could use > it as a CPU mask, and use it to skip nohz CPUs that don't have stale load in > _nohz_idle_balance() (when NOHZ_STATS_KICK).
Yes, you'd need to allocate a second cpumask, worse you need atomic bitops to set and clear bits there. That all _might_ be worth it... dunno.
