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authorNeil Leeder <nleeder@codeaurora.org>2017-02-07 13:14:04 -0500
committerWill Deacon <will.deacon@arm.com>2017-02-08 19:32:24 +0000
commit21bdbb7102edeaebb5ec4ef530c8f442f7562c96 (patch)
tree5f531423c18fe74f1d38144707f51bd21f35a2aa /Documentation/perf
parentfe0a7ef74d1f65b86820a54636323df2b31e0c3f (diff)
downloadlinux-21bdbb7102edeaebb5ec4ef530c8f442f7562c96.tar.bz2
perf: add qcom l2 cache perf events driver
Adds perf events support for L2 cache PMU. The L2 cache PMU driver is named 'l2cache_0' and can be used with perf events to profile L2 events such as cache hits and misses on Qualcomm Technologies processors. Reviewed-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Neil Leeder <nleeder@codeaurora.org> [will: minimise nesting in l2_cache_associate_cpu_with_cluster] [will: use kstrtoul for unsigned long, remove redunant .owner setting] Signed-off-by: Will Deacon <will.deacon@arm.com>
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+Qualcomm Technologies Level-2 Cache Performance Monitoring Unit (PMU)
+=====================================================================
+
+This driver supports the L2 cache clusters found in Qualcomm Technologies
+Centriq SoCs. There are multiple physical L2 cache clusters, each with their
+own PMU. Each cluster has one or more CPUs associated with it.
+
+There is one logical L2 PMU exposed, which aggregates the results from
+the physical PMUs.
+
+The driver provides a description of its available events and configuration
+options in sysfs, see /sys/devices/l2cache_0.
+
+The "format" directory describes the format of the events.
+
+Events can be envisioned as a 2-dimensional array. Each column represents
+a group of events. There are 8 groups. Only one entry from each
+group can be in use at a time. If multiple events from the same group
+are specified, the conflicting events cannot be counted at the same time.
+
+Events are specified as 0xCCG, where CC is 2 hex digits specifying
+the code (array row) and G specifies the group (column) 0-7.
+
+In addition there is a cycle counter event specified by the value 0xFE
+which is outside the above scheme.
+
+The driver provides a "cpumask" sysfs attribute which contains a mask
+consisting of one CPU per cluster which will be used to handle all the PMU
+events on that cluster.
+
+Examples for use with perf:
+
+ perf stat -e l2cache_0/config=0x001/,l2cache_0/config=0x042/ -a sleep 1
+
+ perf stat -e l2cache_0/config=0xfe/ -C 2 sleep 1
+
+The driver does not support sampling, therefore "perf record" will
+not work. Per-task perf sessions are not supported.