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charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On 29/11/24 11:02, Michal Koutný wrote: > On Wed, Nov 27, 2024 at 04:35:39PM GMT, Juri Lelli wrote: > > > The default DL bandwidth is thus is 95%. The fair server is given 5%. > > > Is that 5% of those 95%? > > > > Yes, it is indeed. > > Thanks for navigating me. I have followup questions about > /proc/sys/kernel/sched_rt_runtime_us / /proc/sys/kernel/sched_rt_period_us > (a ratio, without CONGIG_RT_GROUP_SCHED) > > - 0 > - disables DL, (not RT, so they can monopolize a CPU) > - 1 > - DL tasks can monopolize CPU, SCHED_NORMAL have 5% thanks to > fair_server > - 1-Δ > - SCHED_NORMAL tasks have > - (1-Δ)*5% on behalf of DL (above RT) > - Δ regularly (below RT) > > Is this breakdown correct? So, sched_rt_runtime_us/sched_rt_period_us only applies to admission control (for DEADLINE tasks, including dl_servers). The actual parameters controlling the dl_server for SCHED_NORMAL are under sched/ debug as per-cpu values, e.g.: # grep . /sys/kernel/debug/sched/fair_server/cpu*/* /sys/kernel/debug/sched/fair_server/cpu0/period:1000000000 /sys/kernel/debug/sched/fair_server/cpu0/runtime:50000000 /sys/kernel/debug/sched/fair_server/cpu1/period:1000000000 /sys/kernel/debug/sched/fair_server/cpu1/runtime:50000000 /sys/kernel/debug/sched/fair_server/cpu2/period:1000000000 /sys/kernel/debug/sched/fair_server/cpu2/runtime:50000000 /sys/kernel/debug/sched/fair_server/cpu3/period:1000000000 /sys/kernel/debug/sched/fair_server/cpu3/runtime:50000000 /sys/kernel/debug/sched/fair_server/cpu4/period:1000000000 /sys/kernel/debug/sched/fair_server/cpu4/runtime:50000000 /sys/kernel/debug/sched/fair_server/cpu5/period:1000000000 /sys/kernel/debug/sched/fair_server/cpu5/runtime:50000000 /sys/kernel/debug/sched/fair_server/cpu6/period:1000000000 /sys/kernel/debug/sched/fair_server/cpu6/runtime:50000000 /sys/kernel/debug/sched/fair_server/cpu7/period:1000000000 /sys/kernel/debug/sched/fair_server/cpu7/runtime:50000000 You can disable admission control by echoing -1 in sched_rt_runtime_us, but still have the dl_server working for SCHED_NORMAL tasks. By disabling admission control SCHED_DEADLINE can indeed monopolize CPU (over subscription). Best, Juri