| commit | 394ae5fb99c4ae02caa32b1931e65c6821368216 | [log] [tgz] |
|---|---|---|
| author | Venkatesh Srinivas <venkateshs@fuchsia.infra.roller.chromium.org> | Thu May 27 17:51:55 2021 +0000 |
| committer | Copybara-Service <copybara-worker@google.com> | Thu May 27 10:53:14 2021 -0700 |
| tree | 942e9c3887f8217960a6e4191621fb9e13d222b1 | |
| parent | 7894791d3b4e7522d6756ed23a4e06fcacfa39d7 [diff] |
[roll] Roll fuchsia [perf_mon][x86] Reduce required Perf Monitoring version from 4 -> 2
The x86 perf_mon kernel driver and cpu-trace userspace driver drive
the Intel Architectural Performance Monitoring Unit; the kernel and
userspace drivers required a version 4 or newer Performance Monitoring
Unit. (For reference, v4 is supported by Intel Skylake / Intel Goldmont
and newer CPUs natively).
Reduce the minimum required version to version 2; the differences
between version 2 and version 4 are not very large and the existing code
is quite capable of doing basic tracing on the v2 PMU.
Differences between version 2 / 3 & 4:
* Slightly different layout of IA32_PERFEVTSELx
* AnyThread bit (added in v3, but deprecated in v5. We don't use it)
* IA32_PERF_GLOBAL_STATUS freeze indicators
* Freeze_LBRs_ON_PMI -- Fuchsia has disabled support for this, since
we had trouble with this on Skylake CPUs.
Supporting the version 2 and version 3 PMUs adds:
* (minor) Support some pre-Skylake CPUs; notably Broadwell CPUs
* QEMU/KVM only support / emulate the version 2 Architectural
Performance Monitoring Unit, even on newer CPUs. This CR allows us
to use the virtual / emulated PMU on VMs.
Tested:
1) qemu-kvm on Intel Apollo Lake/Goldmont:
$ cpuperf --verbose --spec-file=/pkgfs/packages/cpuperf/0/data/basic-cpu-memory.cpspec
03734:03736> arch_perfmon_start:1484: Enabling perfmon, 2 fixed, 0 programmable, 0 misc
03734:03736> arch_perfmon_stop_locked:1631: Disabling perfmon
|unhalted_reference_cycles|instructions_retired
Trace 0: | 42,733,236| 9,364,816
Trace 1: | 36,898,992| 5,038,940
Trace 2: | 40,587,690| 33,890,484
Trace 3: | 27,410,292| 11,436,008
2) /boot/test/mtrace on Intel Apollo Lake/Goldmont still works
Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/532890
Original-Revision: 257d0784522ad9e194ebe1625284617e71c2f6da
GitOrigin-RevId: 231be4fc2a6fe8943a07786ddde75e799ef32f0c
Change-Id: Iaa37de0ab25bf80725308389afaad917588f4894
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