The changelog is missing the below CCs. :( Since that's a new patch in this series, I expect some feedbacks and thus I'll add them on the next respin.
On 22-Feb 17:01, Patrick Bellasi wrote: > The estimated utilization of a task is currently updated every time the > task is dequeued. However, to keep overheads under control, PELT signals > are effectively updated at maximum once every 1ms. > > Thus, for really short running tasks, it can happen that their util_avg > value has not been updates since their last enqueue. If such tasks are > also frequently running tasks (e.g. the kind of workload generated by > hackbench) it can also happen that their util_avg is updated only every > few activations. > > This means that updating util_est at every dequeue potentially introduces > not necessary overheads and it's also conceptually wrong if the util_avg > signal has never been updated during a task activation. > > Let's introduce a throttling mechanism on task's util_est updates > to sync them with util_avg updates. To make the solution memory > efficient, both in terms of space and load/store operations, we encode a > synchronization flag into the LSB of util_est.enqueued. > This makes util_est an even values only metric, which is still > considered good enough for its purpose. > The synchronization bit is (re)set by __update_load_avg_se() once the > PELT signal of a task has been updated during its last activation. > > Such a throttling mechanism allows to keep under control util_est > overheads in the wakeup hot path, thus making it a suitable mechanism > which can be enabled also on high-intensity workload systems. > Thus, this now switches on by default the estimation utilization > scheduler feature. > > Suggested-by: Chris Redpath <[email protected]> > Signed-off-by: Patrick Bellasi <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Paul Turner <[email protected]> Cc: Vincent Guittot <[email protected]> Cc: Morten Rasmussen <[email protected]> Cc: Dietmar Eggemann <[email protected]> Cc: [email protected] [...] -- #include <best/regards.h> Patrick Bellasi
