Messages in this thread | | | Date | Tue, 29 Mar 2022 20:55:08 +0200 | Subject | Re: [PATCH] arch/arm64: Fix topology initialization for core scheduling | From | Dietmar Eggemann <> |
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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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>> I assume this is for a machine which relies on MPIDR-based setup >> (package_id == -1)? I.e. it doesn't have proper ACPI/(DT) data for >> topology setup. > > Yes, that's my understanding. No PPTT. > >> >> Tried on a ThunderX2 by disabling parse_acpi_topology() but then I end >> up with a machine w/o SMT, so `stress-ng --prctl N` doesn't show this issue. >> >> Which machine were you using? > > 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.
# sudo dmidecode -t 4 | grep "Part Number" Part Number: CN9980-2200LG4077-21-Y-G Part Number: CN9980-2200LG4077-21-Y-G
# cat /sys/devices/system/cpu/cpu0/topology/thread_siblings 0,32,64,96
# cat /sys/kernel/debug/sched/domains/cpu0/domain*/name SMT MC NUMA
But no matter whether I disable parse_acpi_topology() or just force `cpu_topology[cpu].package_id = -1` in this function, I always end up with:
# cat /sys/kernel/debug/sched/domains/cpu0/domain*/name MC NUMA
# cat /sys/devices/system/cpu/cpu0/topology/thread_siblings_list 0
so no SMT sched domain. The MPIDR-based topology fallback code in store_cpu_topology() forces `cpuid_topo->thread_id = -1`.
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?
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