On 20/11/2020 08:55, Peter Zijlstra wrote: [...]
> PELT (Per Entity Load Tracking) > ------------------------------- [...] > Using this we track 2 key metrics: 'running' and 'runnable'. 'Running' > reflects the time an entity spends on the CPU, while 'runnable' reflects the > time an entity spends on the runqueue. When there is only a single task these > two metrics are the same, but once there is contention for the CPU 'running' > will decrease to reflect the fraction of time each task spends on the CPU > while 'runnable' will increase to reflect the amount of contention. People might find it confusing to map 'running and 'runnable' into the 3 PELT signals (load_avg, runnable_avg and util_avg) being used in the scheduler ... with load_avg being 'runnable' and 'weight' based. > For more detail see: kernel/sched/pelt.c > > > Frequency- / Heterogeneous Invariance > ------------------------------------- We call 'Heterogeneous Invariance' CPU invariance in chapter 2.3 Documentation/scheduler/sched-capacity.rst. [...] > For more detail see: > > - kernel/sched/pelt.h:update_rq_clock_pelt() > - arch/x86/kernel/smpboot.c:"APERF/MPERF frequency ratio computation." drivers/base/arch_topology.c:"f_cur/f_max ratio computation". > UTIL_EST / UTIL_EST_FASTUP > -------------------------- [...] > util_est := \Sum_t max( t_running, t_util_est_ewma ) > > For more detail see: kernel/sched/fair.h:util_est_dequeue() s/fair.h/fair.c > UCLAMP > ------ > > It is possible to set effective u_min and u_max clamps on each task; the s/on each task/on each CFS or RT task [...]