On Mon, Nov 23, 2020 at 10:26:13AM +0100, Dietmar Eggemann wrote: > 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.
Yeah, but that's for another document, I suppose. much of pelt.c uses runnable. Also, the comment that goes with struct sched_avg should explain. > > 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. > > [...] Fair enough; I've renamed it to match. > > 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". I can't seem to find that in any tree near me (I tried tip/master and next/master) > > 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 Thanks!
