From: Andi Kleen <a...@linux.intel.com> Initial attempt of documenting the perf sysfs interface as an ABI. I also added some additional pointers hopefully useful to the users. Comments welcome.
Cc: Vince Weaver <vincent.wea...@maine.edu> Cc: jo...@redhat.com Signed-off-by: Andi Kleen <a...@linux.intel.com> --- Documentation/ABI/stable/sysfs-devices-perf | 87 +++++++++++++++++++++++++++++ 1 file changed, 87 insertions(+) create mode 100644 Documentation/ABI/stable/sysfs-devices-perf diff --git a/Documentation/ABI/stable/sysfs-devices-perf b/Documentation/ABI/stable/sysfs-devices-perf new file mode 100644 index 0000000..0b00c7c --- /dev/null +++ b/Documentation/ABI/stable/sysfs-devices-perf @@ -0,0 +1,87 @@ +Perf events enumeration in sysfs + +The perf events subsystem exports the format of hardware performance +counter events supported by perf events. The events can be accessed +using the perf_event_open() syscall. Each directory represents +a PMU (Performance Monitoring Unit) + +What: /sys/devices/*/format/* +Description: + +Each file in format describes how to fill in an event attribute on the +current CPU for the perf_event_open syscall. Multiple event +attributes may be overlapping and only be valid for some combination +of attributes (for example only for some event/umask combinations). +Most attributes are optional. + +Each field may have the following contents: + +CONFIG:START-END Field contains of bits START-END in the perf_event_attr CONFIG field +CONFIG:BIT Field consists of a single bit with index BIT in CONFIG field + +Valid CONFIG fields are config, config1, config2. These map to the respective 64bit words +in the struct perf_event_attr. + +Typical attributes on a x86 platform + +event Set the 8 bit event code (required) +umask Set the 8 bit umask. Event code and umask together select an hardware event. +cmask Set the 8 bit counter Mask. Only increment counters when more than cmask + events happen at the same time. +inv (1bit flag) Invert the event condition +edge (1bit flag) Only increment the event when the condition changes (starts happening) +any (1bit flag) Count on both threads of a core +pc (1bit flag) Toggle the PMi pins when the condition happens + +Attributes available on some x86 platforms: + +in_tx (1bit flag) Only count in a hardware transaction. +in_tx_cp (1bit flag) Undo counts inside transaction when transaction aborts. +ldlat Set the load-use latency threshold for sampling loads. + Note this is a load-use latency so includes pipeline delays. +offcore_rsp Set an extra mask qualifying the type of offcore access. + Only with OFFCORE_RESPONSE events + +For more details on the x86 attributes on Intel platforms please see +http://www.intel.com/sdm Volume 3, Chapter 18 and 19. For more +details on the perf_event_attr struct please see the perf_event_open +manpage. + +What: /sys/devices/*/events/* +Description: + +Describe predefined events available in the CPU. Each file describes an event. +The format is attr=0xHEXNUM{,attr=0xHEXNUM}. Each attr is described in a config +file. Together all the attributes can be used to set up a valid event for the +perf_event_open syscall. + +Note typically only a small subset of the CPU events are described +Some more events are available through predefined classes in perf_event_attr. + +What: /sys/devices/*/type +Description: + +Contains a decimal number. The PMU type to fill into perf_event_attr in the +type field to select the correct PMU. + +What: /sys/devices/*/perf_event_mux_interval_ms +Description: + +Decimal number. Set the counter multiplexing interval in ms. When more +events are active than the hardware directly supports perf events +multiplexes the event. By default this is done on timer interrupts +(depending on the CONFIG_HZ setting) and not done while idle. This +allows to set a different frequency. Note that setting this may impact +idle time, as the event switches will wake up the CPUs now. + +What: /sys/devices/*/rdpmc +Description: + +[x86] When 1, allow the RDPMC instruction in user space to read performance +events that have been set up with perf. + +Users: perf (tools/perf/*) +The following libraries provide more user friendly interfaces: + PAPI (http://icl.cs.utk.edu/papi/) + libpfm4 (http://perfmon2.sourceforge.net/) + jevents (http://github.com/andikleen/pmu-tools) -- 1.9.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
