Re: [Xen-devel] RTDS with extra time issue

[Andrii Anisov <andrii_anisov@xxxxxxxx>]

Hello Dario,


I eventually used your old email.

Please take a look here.


On 09.02.18 14:20, Andrii Anisov wrote:
> Dear Dario,
>
> Now I'm experimenting with RTDS, in particular with "extra time" 
> functionality.
> My experimental setup is built on Salvator-X board with H3 SOC 
> (running only big cores cluster, 4xA57).
> Domains up and running, and their VCPU are as following:
>
> root@generic-armv8-xt-dom0:/xt/dom.cfg# xl sched-rtds -v all
> Cpupool Pool-0: sched=RTDS
> Name                                ID VCPU    Period    Budget Extratime
> (XEN) FLASK: Allowing unknown domctl_scheduler_op: 3.
> Domain-0                             0    0     10000 1000 yes
> Domain-0                             0    1     10000 1000 yes
> Domain-0                             0    2     10000 1000 yes
> Domain-0                             0    3     10000 1000 yes
> (XEN) FLASK: Allowing unknown domctl_scheduler_op: 3.
> DomR                                 3    0     10000 5000 no
> (XEN) FLASK: Allowing unknown domctl_scheduler_op: 3.
> DomA                                 5    0     10000 1000 yes
> DomA                                 5    1     10000 1000 yes
> DomA                                 5    2     10000 1000 yes
> DomA                                 5    3     10000 1000 yes
> (XEN) FLASK: Allowing unknown domctl_scheduler_op: 3.
> DomD                                 6    0     10000 1000 yes
> DomD                                 6    1     10000 1000 yes
> DomD                                 6    2     10000 1000 yes
> DomD                                 6    3     10000 1000 yes
>
> The idea of such configuration is that only DomR really runs RT tasks, 
> and their CPU utilization would be less than half a CPU. Rest of the 
> domains are application domains without need of RT guarantees for 
> their tasks, but can utilize as much CPU as they need and is available 
> at this moment.
> I load application domains with `dd if=/dev/zero of=/dev/null` per VCPU.
> In DomR I run one RT task with period 10ms and wcet 4ms (I'm using 
> LITMUS-RT for DomR), and see that this task sometime misses its 
> deadline. Which means that the only VCPU of DomR haven't got its 5ms 
> each 10ms.
> The ps in DomR is as following:
>
> root@genericarmv8:~# ps
>   PID USER       VSZ STAT COMMAND
>     1 root      1764 S    init
>     2 root         0 SW   [kthreadd]
>     3 root         0 SW   [ksoftirqd/0]
>     4 root         0 SW   [kworker/0:0]
>     5 root         0 SW<  [kworker/0:0H]
>     6 root         0 SW   [kworker/u2:0]
>     7 root         0 SW   [rcu_preempt]
>     8 root         0 SW   [rcu_sched]
>     9 root         0 SW   [rcu_bh]
>    10 root         0 SW   [migration/0]
>    11 root         0 SW<  [lru-add-drain]
>    12 root         0 SW   [watchdog/0]
>    13 root         0 SW   [cpuhp/0]
>    14 root         0 SW   [kdevtmpfs]
>    15 root         0 SW<  [netns]
>    16 root         0 SW   [kworker/u2:1]
>    17 root         0 SW   [xenwatch]
>    18 root         0 SW   [xenbus]
>   360 root         0 SW   [khungtaskd]
>   361 root         0 SW   [oom_reaper]
>   362 root         0 SW<  [writeback]
>   364 root         0 SW   [kcompactd0]
>   365 root         0 SWN  [ksmd]
>   366 root         0 SW<  [crypto]
>   367 root         0 SW<  [kintegrityd]
>   368 root         0 SW<  [bioset]
>   370 root         0 SW<  [kblockd]
>   388 root         0 SW<  [ata_sff]
>   394 root         0 SW   [kworker/0:1]
>   433 root         0 SW<  [watchdogd]
>   519 root         0 SW<  [rpciod]
>   520 root         0 SW<  [xprtiod]
>   548 root         0 SW   [kswapd0]
>   549 root         0 SW<  [vmstat]
>   633 root         0 SW<  [nfsiod]
>   802 root         0 SW   [khvcd]
>   844 root         0 SW<  [bioset]
>   847 root         0 SW<  [bioset]
>   850 root         0 SW<  [bioset]
>   853 root         0 SW<  [bioset]
>   856 root         0 SW<  [bioset]
>   859 root         0 SW<  [bioset]
>   861 root         0 SW<  [bioset]
>   864 root         0 SW<  [bioset]
>   946 root         0 SW<  [vfio-irqfd-clea]
>  1405 root      2912 S    {start_getty} /bin/sh /bin/start_getty 
> 115200 hvc0 vt102
>  1406 root      2976 S    /sbin/getty 38400 tty1
>  1407 root      3256 S    -sh
>  1512 root      2908 S    {st-trace-schedu} /bin/bash 
> /usr/sbin/st-trace-schedule -s m1
>  1523 root      1932 S    rtspin -a 194000 -w 48 100 120
>  1527 root      1748 S    /usr/sbin/ftcat -p /tmp/tmp.3PXDeo/cpu0.pid 
> /dev/litmus/sched_trace0 501 502 503 504 505 506 507 508 509 510 511
>  1533 root      3224 R    ps
>
> I noticed that behavior while running EPAM demo setup. Which consists 
> of HW drivers in DomD, PV Drivers backends in DomD, DomA running real 
> Android with PV Drivers and utilizing GPU sharing, etc.
> But I managed to reproduce the issue when all domains are running 
> generic armv8 kernel with minimal initramfses.
> So I suspect an issue in RTDS.
--

*Andrii Anisov*



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