tools/perf/Documentation/intel-hybrid.txt

Source file repositories/reference/linux-study-clean/tools/perf/Documentation/intel-hybrid.txt

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Linux kernel
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tools/perf/Documentation/intel-hybrid.txt
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.txt
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Support Tooling And Documentation
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tools
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Support Tooling And Documentation: documentation
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Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

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Intel hybrid support
--------------------
Support for Intel hybrid events within perf tools.

For some Intel platforms, such as AlderLake, which is hybrid platform and
it consists of atom cpu and core cpu. Each cpu has dedicated event list.
Part of events are available on core cpu, part of events are available
on atom cpu and even part of events are available on both.

Kernel exports two new cpu pmus via sysfs:
/sys/bus/event_source/devices/cpu_core
/sys/bus/event_source/devices/cpu_atom

The 'cpus' files are created under the directories. For example,

cat /sys/bus/event_source/devices/cpu_core/cpus
0-15

cat /sys/bus/event_source/devices/cpu_atom/cpus
16-23

It indicates cpu0-cpu15 are core cpus and cpu16-cpu23 are atom cpus.

As before, use perf-list to list the symbolic event.

perf list

inst_retired.any
	[Fixed Counter: Counts the number of instructions retired. Unit: cpu_atom]
inst_retired.any
	[Number of instructions retired. Fixed Counter - architectural event. Unit: cpu_core]

The 'Unit: xxx' is added to brief description to indicate which pmu
the event is belong to. Same event name but with different pmu can
be supported.

Enable hybrid event with a specific pmu

To enable a core only event or atom only event, following syntax is supported:

	cpu_core/<event name>/
or
	cpu_atom/<event name>/

For example, count the 'cycles' event on core cpus.

	perf stat -e cpu_core/cycles/

Create two events for one hardware event automatically

When creating one event and the event is available on both atom and core,
two events are created automatically. One is for atom, the other is for
core. Most of hardware events and cache events are available on both
cpu_core and cpu_atom.

For hardware events, they have pre-defined configs (e.g. 0 for cycles).
But on hybrid platform, kernel needs to know where the event comes from
(from atom or from core). The original perf event type PERF_TYPE_HARDWARE
can't carry pmu information. So now this type is extended to be PMU aware
type. The PMU type ID is stored at attr.config[63:32].

PMU type ID is retrieved from sysfs.
/sys/bus/event_source/devices/cpu_atom/type
/sys/bus/event_source/devices/cpu_core/type

The new attr.config layout for PERF_TYPE_HARDWARE:

PERF_TYPE_HARDWARE:                 0xEEEEEEEE000000AA
                                    AA: hardware event ID
                                    EEEEEEEE: PMU type ID

Annotation

Implementation Notes