42 lines
1.5 KiB
Plaintext
42 lines
1.5 KiB
Plaintext
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STM32 DDR Performance Monitor (DDRPERFM)
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========================================
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The DDRPERFM is the DDR Performance Monitor embedded in STM32MP1 SOC.
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See STM32MP157 reference manual RM0436 to get a description of this peripheral.
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The five following counters are supported by stm32-ddr-pmu driver:
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cnt0: read operations counters (read_cnt)
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cnt1: write operations counters (write_cnt)
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cnt2: active state counters (activate_cnt)
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cnt3: idle state counters (idle_cnt)
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tcnt: time count, present for all sets (time_cnt)
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The stm32-ddr-pmu driver relies on the perf PMU framework to expose the
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counters via sysfs:
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$ ls /sys/bus/event_source/devices/ddrperfm/events
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activate_cnt idle_cnt read_cnt time_cnt write_cnt
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The perf PMU framework is usually invoked via the 'perf stat' tool.
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The DDRPERFM is a system monitor that cannot isolate the traffic coming from a
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given thread or CPU, that is why stm32-ddr-pmu driver rejects any 'perf stat'
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call that does not request a system-wide collection: the '-a, --all-cpus'
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option is mandatory!
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Example:
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$ perf stat -e ddrperfm/read_cnt/,ddrperfm/time_cnt/ -a sleep 20
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Performance counter stats for 'system wide':
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342541560 ddrperfm/read_cnt/
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10660011400 ddrperfm/time_cnt/
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20.021068551 seconds time elapsed
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The driver also exposes a 'bandwidth' attribute that can be used to display
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the read/write/total bandwidth achieved during the last 'perf stat' execution.
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$ cat /sys/bus/event_source/devices/ddrperfm/bandwidth
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Read = 403, Write = 239, Read & Write = 642 (MB/s)
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