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| -rw-r--r-- | tools/perf/Documentation/intel-hybrid.txt | 204 |
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diff --git a/tools/perf/Documentation/intel-hybrid.txt b/tools/perf/Documentation/intel-hybrid.txt new file mode 100644 index 000000000..e7a776ad2 --- /dev/null +++ b/tools/perf/Documentation/intel-hybrid.txt @@ -0,0 +1,204 @@ +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/devices/cpu_core +/sys/devices/cpu_atom + +The 'cpus' files are created under the directories. For example, + +cat /sys/devices/cpu_core/cpus +0-15 + +cat /sys/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/devices/cpu_atom/type +/sys/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 + +Cache event is similar. The type PERF_TYPE_HW_CACHE is extended to be +PMU aware type. The PMU type ID is stored at attr.config[63:32]. + +The new attr.config layout for PERF_TYPE_HW_CACHE: + +PERF_TYPE_HW_CACHE: 0xEEEEEEEE00DDCCBB + BB: hardware cache ID + CC: hardware cache op ID + DD: hardware cache op result ID + EEEEEEEE: PMU type ID + +When enabling a hardware event without specified pmu, such as, +perf stat -e cycles -a (use system-wide in this example), two events +are created automatically. + + ------------------------------------------------------------ + perf_event_attr: + size 120 + config 0x400000000 + sample_type IDENTIFIER + read_format TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING + disabled 1 + inherit 1 + exclude_guest 1 + ------------------------------------------------------------ + +and + + ------------------------------------------------------------ + perf_event_attr: + size 120 + config 0x800000000 + sample_type IDENTIFIER + read_format TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING + disabled 1 + inherit 1 + exclude_guest 1 + ------------------------------------------------------------ + +type 0 is PERF_TYPE_HARDWARE. +0x4 in 0x400000000 indicates it's cpu_core pmu. +0x8 in 0x800000000 indicates it's cpu_atom pmu (atom pmu type id is random). + +The kernel creates 'cycles' (0x400000000) on cpu0-cpu15 (core cpus), +and create 'cycles' (0x800000000) on cpu16-cpu23 (atom cpus). + +For perf-stat result, it displays two events: + + Performance counter stats for 'system wide': + + 6,744,979 cpu_core/cycles/ + 1,965,552 cpu_atom/cycles/ + +The first 'cycles' is core event, the second 'cycles' is atom event. + +Thread mode example: + +perf-stat reports the scaled counts for hybrid event and with a percentage +displayed. The percentage is the event's running time/enabling time. + +One example, 'triad_loop' runs on cpu16 (atom core), while we can see the +scaled value for core cycles is 160,444,092 and the percentage is 0.47%. + +perf stat -e cycles \-- taskset -c 16 ./triad_loop + +As previous, two events are created. + +------------------------------------------------------------ +perf_event_attr: + size 120 + config 0x400000000 + sample_type IDENTIFIER + read_format TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING + disabled 1 + inherit 1 + enable_on_exec 1 + exclude_guest 1 +------------------------------------------------------------ + +and + +------------------------------------------------------------ +perf_event_attr: + size 120 + config 0x800000000 + sample_type IDENTIFIER + read_format TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING + disabled 1 + inherit 1 + enable_on_exec 1 + exclude_guest 1 +------------------------------------------------------------ + + Performance counter stats for 'taskset -c 16 ./triad_loop': + + 233,066,666 cpu_core/cycles/ (0.43%) + 604,097,080 cpu_atom/cycles/ (99.57%) + +perf-record: + +If there is no '-e' specified in perf record, on hybrid platform, +it creates two default 'cycles' and adds them to event list. One +is for core, the other is for atom. + +perf-stat: + +If there is no '-e' specified in perf stat, on hybrid platform, +besides of software events, following events are created and +added to event list in order. + +cpu_core/cycles/, +cpu_atom/cycles/, +cpu_core/instructions/, +cpu_atom/instructions/, +cpu_core/branches/, +cpu_atom/branches/, +cpu_core/branch-misses/, +cpu_atom/branch-misses/ + +Of course, both perf-stat and perf-record support to enable +hybrid event with a specific pmu. + +e.g. +perf stat -e cpu_core/cycles/ +perf stat -e cpu_atom/cycles/ +perf stat -e cpu_core/r1a/ +perf stat -e cpu_atom/L1-icache-loads/ +perf stat -e cpu_core/cycles/,cpu_atom/instructions/ +perf stat -e '{cpu_core/cycles/,cpu_core/instructions/}' + +But '{cpu_core/cycles/,cpu_atom/instructions/}' will return +warning and disable grouping, because the pmus in group are +not matched (cpu_core vs. cpu_atom). |