Messages in this thread | | | Date | Wed, 30 Mar 2022 17:48:34 +0200 | Subject | Re: [PATCH] arch/arm64: Fix topology initialization for core scheduling | From | Dietmar Eggemann <> |
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On 29/03/2022 21:50, Phil Auld wrote: > On Tue, Mar 29, 2022 at 08:55:08PM +0200 Dietmar Eggemann wrote: >> On 29/03/2022 17:20, Phil Auld wrote: >>> On Tue, Mar 29, 2022 at 04:02:22PM +0200 Dietmar Eggemann wrote: >>>> On 22/03/2022 17:03, Phil Auld wrote:
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>>> This instance is an HPE Apollo 70 set to smt-4. I believe it's ThunderX2 >>> chips. >>> >>> ARM (CN9980-2200LG4077-Y21-G) >> I'm using the same processor just with ACPI/PPTT. >> > > Maybe I'm misinformed about these systems having no PPTT... > > I'm reclaiming the system. Is there a way I can tell from userspace?
# cat /sys/firmware/acpi/tables/PPTT > pptt.dat # iasl -d pptt.dat # vim pptt.dsl
[...]
>> so no SMT sched domain. The MPIDR-based topology fallback code in >> store_cpu_topology() forces `cpuid_topo->thread_id = -1`. > > Right. So since I'm getting SMT it must not have package_id == -1. > In which case you should be able to reproduce it because it must > be that the call the update_siblings_masks() is required. That > appears to only be called from store_cpu_topology() which is > after the scheduler has already setup the core pointers. > > The fix could be the same but I should reword the commit message > since it should effect all SMT arm systems I'd think. > > Or maybe the ACPI topology code should call update_sibling_masks(). >> >> IMHO this is why on my machine I don't see this issue while running: >> >> root@oss-apollo7007:~# stress-ng --prctl 256 -t 60 >> stress-ng: info: [2388042] dispatching hogs: 256 prctl >> >> Is there something I miss in my setup to provoke this issue? >> > > Make sure you have a stress-ng that is new enough and built against > headers that have the CORE_SCHED prctls defined.
Ah, I was using a pretty old version 0.11.07. Now I switched to 0.13.12 which includes:
9038e442b92d - stress-prctl: add Linux 5.14 PR_SCHED_CORE prctl
To get SCHED_CORE activated in stress-prctl.c, as a quick hack, I had to add the definitions of PR_SCHED_CORE, PR_SCHED_CORE_GET, etc. to this file.
Now the issue you described triggers on this machine immediately.
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