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49 lines
2.3 KiB
49 lines
2.3 KiB
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APM X-Gene SoC Performance Monitoring Unit (PMU) |
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X-Gene SoC PMU consists of various independent system device PMUs such as |
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L3 cache(s), I/O bridge(s), memory controller bridge(s) and memory |
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controller(s). These PMU devices are loosely architected to follow the |
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same model as the PMU for ARM cores. The PMUs share the same top level |
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interrupt and status CSR region. |
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PMU (perf) driver |
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The xgene-pmu driver registers several perf PMU drivers. Each of the perf |
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driver provides description of its available events and configuration options |
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in sysfs, see /sys/devices/<l3cX/iobX/mcbX/mcX>/. |
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The "format" directory describes format of the config (event ID), |
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config1 (agent ID) fields of the perf_event_attr structure. The "events" |
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directory provides configuration templates for all supported event types that |
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can be used with perf tool. For example, "l3c0/bank-fifo-full/" is an |
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equivalent of "l3c0/config=0x0b/". |
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Most of the SoC PMU has a specific list of agent ID used for monitoring |
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performance of a specific datapath. For example, agents of a L3 cache can be |
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a specific CPU or an I/O bridge. Each PMU has a set of 2 registers capable of |
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masking the agents from which the request come from. If the bit with |
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the bit number corresponding to the agent is set, the event is counted only if |
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it is caused by a request from that agent. Each agent ID bit is inversely mapped |
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to a corresponding bit in "config1" field. By default, the event will be |
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counted for all agent requests (config1 = 0x0). For all the supported agents of |
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each PMU, please refer to APM X-Gene User Manual. |
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Each perf driver also provides a "cpumask" sysfs attribute, which contains a |
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single CPU ID of the processor which will be used to handle all the PMU events. |
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Example for perf tool use:: |
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/ # perf list | grep -e l3c -e iob -e mcb -e mc |
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l3c0/ackq-full/ [Kernel PMU event] |
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<...> |
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mcb1/mcb-csw-stall/ [Kernel PMU event] |
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/ # perf stat -a -e l3c0/read-miss/,mcb1/csw-write-request/ sleep 1 |
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/ # perf stat -a -e l3c0/read-miss,config1=0xfffffffffffffffe/ sleep 1 |
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The driver does not support sampling, therefore "perf record" will |
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not work. Per-task (without "-a") perf sessions are not supported.
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