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