Processwatch: Add support for AMD Zen processors#13
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Processwatch uses software pmu cpu-clock event if it fails to detect
the architecture. Although it works, cpu-clock event is imprecise. On
AMD, ibs_op// pmu provides precise sampling, so port Processwatch to
use ibs_op// on AMD.
Notes:
o Processwatch with systemwide mode is supported with all versions of
kernel. However, IBS on Linux supports per-process sampling only with
v6.2 and later kernels. Thus processwatch with per-process mode
(--pid=[pid] / -p option) is supported only with v6.2 and later.
o Processwatch fails to run with "WARNING: CPU xxx is offline." on AMD
machines where some cores fused off in the hw. The issue is with how
kernel exposes number of possible cpus in the sysfs. Below kernel
patches fixed the issue.
v5.16 aa06e20f1be6 ("x86/ACPI: Don't add CPUs that are not online
capable")
v6.3 e2869bd7af60 ("x86/acpi/boot: Do not register processors that
cannot be onlined for x2APIC")
o Currently IBS is not supported in KVM guest and thus Processwatch
falls back to cpu-clock event when run inside the KVM guest.
o TMA support is not added for AMD.
Signed-off-by: Ravi Bangoria <ravi.bangoria@amd.com>
matthew-olson-intel
approved these changes
May 1, 2024
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matthew-olson-intel
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This looks great! Thanks for doing this. I don't have access to a system to test it right now, but I'll take your word for it ;D
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Processwatch uses software pmu cpu-clock event if it fails to detect the architecture. Although it works, cpu-clock event is imprecise. On AMD, ibs_op// pmu provides precise sampling, so port Processwatch to use ibs_op// on AMD platforms.