On 10/02/2025 18:09, Juri Lelli wrote: > Hi Christian, > > Thanks for taking a look as well. > > On 07/02/25 15:55, Christian Loehle wrote: >> On 2/7/25 14:04, Jon Hunter wrote: >>> >>> >>> On 07/02/2025 13:38, Dietmar Eggemann wrote: >>>> On 07/02/2025 11:38, Jon Hunter wrote: >>>>> >>>>> On 06/02/2025 09:29, Juri Lelli wrote: >>>>>> On 05/02/25 16:56, Jon Hunter wrote: >>>>>> >>>>>> ... >>>>>> >>>>>>> Thanks! That did make it easier :-) >>>>>>> >>>>>>> Here is what I see ... >>>>>> >>>>>> Thanks! >>>>>> >>>>>> Still different from what I can repro over here, so, unfortunately, I >>>>>> had to add additional debug printks. Pushed to the same branch/repo. >>>>>> >>>>>> Could I ask for another run with it? Please also share the complete >>>>>> dmesg from boot, as I would need to check debug output when CPUs are >>>>>> first onlined. >>>> >>>> So you have a system with 2 big and 4 LITTLE CPUs (Denver0 Denver1 A57_0 >>>> A57_1 A57_2 A57_3) in one MC sched domain and (Denver1 and A57_0) are >>>> isol CPUs? >>> >>> I believe that 1-2 are the denvers (even thought they are listed as 0-1 in device-tree). >> >> Interesting, I have yet to reproduce this with equal capacities in isolcpus. >> Maybe I didn't try hard enough yet. >> >>> >>>> This should be easy to set up for me on my Juno-r0 [A53 A57 A57 A53 A53 A53] >>> >>> Yes I think it is similar to this. >>> >>> Thanks! >>> Jon >>> >> >> I could reproduce that on a different LLLLbb with isolcpus=3,4 (Lb) and >> the offlining order: >> echo 0 > /sys/devices/system/cpu/cpu5/online >> echo 0 > /sys/devices/system/cpu/cpu1/online >> echo 0 > /sys/devices/system/cpu/cpu3/online >> echo 0 > /sys/devices/system/cpu/cpu2/online >> echo 0 > /sys/devices/system/cpu/cpu4/online >> >> while the following offlining order succeeds: >> echo 0 > /sys/devices/system/cpu/cpu5/online >> echo 0 > /sys/devices/system/cpu/cpu4/online >> echo 0 > /sys/devices/system/cpu/cpu1/online >> echo 0 > /sys/devices/system/cpu/cpu2/online >> echo 0 > /sys/devices/system/cpu/cpu3/online >> (Both offline an isolcpus last, both have CPU0 online) >> Could reproduce on Juno-r0: 0 1 2 3 4 5 L b b L L L ^^^ isol = [3-4] so both L echo 0 > /sys/devices/system/cpu/cpu1/online echo 0 > /sys/devices/system/cpu/cpu4/online echo 0 > /sys/devices/system/cpu/cpu5/online echo 0 > /sys/devices/system/cpu/cpu2/online - isol echo 0 > /sys/devices/system/cpu/cpu3/online - isol >> The issue only triggers with sugov DL threads (I guess that's obvious, but >> just to mention it). IMHO, it doesn't have to be a sugov DL task. Any DL task will do. // on a 2. shell: # chrt -d -T 5000000 -D 10000000 -P 16666666 -p 0 $$ # ps -eTo comm,pid,class | grep DLN bash 1243 DLN 5000000/16666666 = 0.3, 0.3 << 10 = 307 (task util, bandwidth requirement) > It wasn't obvious to me at first :). So thanks for confirming. > >> I'll investigate some more later but wanted to share for now. > > So, problem actually is that I am not yet sure what we should do with > sugovs' bandwidth wrt root domain accounting. W/o isolation it's all > good, as it gets accounted for correctly on the dynamic domains sugov > tasks can run on. But with isolation and sugov affected_cpus that cross > isolation domains (e.g., one BIG one little), we can get into troubles > not knowing if sugov contribution should fall on the DEF or DYN domain. # echo 0 > /sys/devices/system/cpu/cpu1/online [ 87.402722] __dl_bw_capacity() mask=0-2,5 cap=2940 [ 87.407551] dl_bw_cpus() cpu=1 rd->span=0-2,5 cpu_active_mask=0-5 cpumask_weight(rd->span)=4 [ 87.416019] dl_bw_manage: cpu=1 cap=1916 fair_server_bw=52428 total_bw=524284 dl_bw_cpus=4 type=DYN span=0-2,5 # echo 0 > /sys/devices/system/cpu/cpu2/online [ 95.562270] __dl_bw_capacity() mask=0,2,5 cap=1916 [ 95.567091] dl_bw_cpus() cpu=2 rd->span=0,2,5 cpu_active_mask=0,2-5 cpumask_weight(rd->span)=3 [ 95.575735] dl_bw_manage: cpu=2 cap=892 fair_server_bw=52428 total_bw=157284 dl_bw_cpus=3 type=DYN span=0,2,5 # echo 0 > /sys/devices/system/cpu/cpu5/online [ 100.573131] __dl_bw_capacity() mask=0,5 cap=892 [ 100.577713] dl_bw_cpus() cpu=5 rd->span=0,5 cpu_active_mask=0,3-5 cpumask_weight(rd->span)=2 [ 100.586186] dl_bw_manage: cpu=5 cap=446 fair_server_bw=52428 total_bw=104856 dl_bw_cpus=2 type=DYN span=0,5 # echo 0 > /sys/devices/system/cpu/cpu3/online [ 110.232755] __dl_bw_capacity() mask=1-5 cap=892 [ 110.237333] dl_bw_cpus() cpu=6 rd->span=1-5 cpu_active_mask=0,3-4 cpus=2 [ 110.244064] dl_bw_manage: cpu=3 cap=446 fair_server_bw=52428 total_bw=419428 dl_bw_cpus=2 type=DEF span=1-5 # echo 0 > /sys/devices/system/cpu/cpu4/online [ 175.870273] __dl_bw_capacity() mask=1-5 cap=446 [ 175.874850] dl_bw_cpus() cpu=6 rd->span=1-5 cpu_active_mask=0,4 cpus=1 [ 175.881407] dl_bw_manage: cpu=4 cap=0 fair_server_bw=52428 total_bw=367000 dl_bw_cpus=1 type=DEF span=1-5 ^^^^^ ^^^^^^^^ w/o/ cpu4 cap is 0! cpu0 is not part of it ... [ 175.897600] dl_bw_manage() cpu=4 cap=0 overflow=1 return=-16 ^^^^^^^^^^ -EBUSY -bash: echo: write error: Device or resource busy sched_cpu_deactivate() dl_bw_deactivate(cpu) dl_bw_manage(dl_bw_req_deactivate, cpu, 0); return overflow ? -EBUSY : 0; Looks like in DEF there is no CPU capacity left but we still have 1 DLN task with a bandwidth requirement of 307.