[tip:perf/urgent] perf tools: Add README for info on parsing JSON/map files

From: tip-bot for Sukadev Bhattiprolu
Date: Tue Oct 04 2016 - 04:18:10 EST

Commit-ID: 06d839b4f712065d76cba92e7e10e9d771771c5a
Gitweb: http://git.kernel.org/tip/06d839b4f712065d76cba92e7e10e9d771771c5a
Author: Sukadev Bhattiprolu <sukadev@xxxxxxxxxxxxxxxxxx>
AuthorDate: Thu, 15 Sep 2016 15:24:52 -0700
Committer: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitDate: Mon, 3 Oct 2016 21:37:48 -0300

perf tools: Add README for info on parsing JSON/map files

Signed-off-by: Sukadev Bhattiprolu <sukadev@xxxxxxxxxxxxxxxxxx>
Acked-by: Ingo Molnar <mingo@xxxxxxxxxx>
Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Madhavan Srinivasan <maddy@xxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: linuxppc-dev@xxxxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/1473978296-20712-16-git-send-email-sukadev@xxxxxxxxxxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
tools/perf/pmu-events/README | 147 +++++++++++++++++++++++++++++++++++++++++++
1 file changed, 147 insertions(+)

diff --git a/tools/perf/pmu-events/README b/tools/perf/pmu-events/README
new file mode 100644
index 0000000..1408ade
--- /dev/null
+++ b/tools/perf/pmu-events/README
@@ -0,0 +1,147 @@
+The contents of this directory allow users to specify PMU events in their
+CPUs by their symbolic names rather than raw event codes (see example below).
+The main program in this directory, is the 'jevents', which is built and
+executed _BEFORE_ the perf binary itself is built.
+The 'jevents' program tries to locate and process JSON files in the directory
+tree tools/perf/pmu-events/arch/foo.
+ - Regular files with '.json' extension in the name are assumed to be
+ JSON files, each of which describes a set of PMU events.
+ - Regular files with basename starting with 'mapfile.csv' are assumed
+ to be a CSV file that maps a specific CPU to its set of PMU events.
+ (see below for mapfile format)
+ - Directories are traversed, but all other files are ignored.
+The PMU events supported by a CPU model are expected to grouped into topics
+such as Pipelining, Cache, Memory, Floating-point etc. All events for a topic
+should be placed in a separate JSON file - where the file name identifies
+the topic. Eg: "Floating-point.json".
+All the topic JSON files for a CPU model/family should be in a separate
+sub directory. Thus for the Silvermont X86 CPU:
+ $ ls tools/perf/pmu-events/arch/x86/Silvermont_core
+ Cache.json Memory.json Virtual-Memory.json
+ Frontend.json Pipeline.json
+Using the JSON files and the mapfile, 'jevents' generates the C source file,
+'pmu-events.c', which encodes the two sets of tables:
+ - Set of 'PMU events tables' for all known CPUs in the architecture,
+ (one table like the following, per JSON file; table name 'pme_power8'
+ is derived from JSON file name, 'power8.json').
+ struct pmu_event pme_power8[] = {
+ ...
+ {
+ .name = "pm_1plus_ppc_cmpl",
+ .event = "event=0x100f2",
+ .desc = "1 or more ppc insts finished,",
+ },
+ ...
+ }
+ - A 'mapping table' that maps each CPU of the architecture, to its
+ 'PMU events table'
+ struct pmu_events_map pmu_events_map[] = {
+ {
+ .cpuid = "004b0000",
+ .version = "1",
+ .type = "core",
+ .table = pme_power8
+ },
+ ...
+ };
+After the 'pmu-events.c' is generated, it is compiled and the resulting
+'pmu-events.o' is added to 'libperf.a' which is then used to build perf.
+ 1. Several CPUs can support same set of events and hence use a common
+ JSON file. Hence several entries in the pmu_events_map[] could map
+ to a single 'PMU events table'.
+ 2. The 'pmu-events.h' has an extern declaration for the mapping table
+ and the generated 'pmu-events.c' defines this table.
+ 3. _All_ known CPU tables for architecture are included in the perf
+ binary.
+At run time, perf determines the actual CPU it is running on, finds the
+matching events table and builds aliases for those events. This allows
+users to specify events by their name:
+ $ perf stat -e pm_1plus_ppc_cmpl sleep 1
+where 'pm_1plus_ppc_cmpl' is a Power8 PMU event.
+In case of errors when processing files in the tools/perf/pmu-events/arch
+directory, 'jevents' tries to create an empty mapping file to allow the perf
+build to succeed even if the PMU event aliases cannot be used.
+However some errors in processing may cause the perf build to fail.
+Mapfile format
+The mapfile enables multiple CPU models to share a single set of PMU events.
+It is required even if such mapping is 1:1.
+The mapfile.csv format is expected to be:
+ Header line
+ CPUID,Version,Dir/path/name,Type
+ Comma:
+ is the required field delimiter (i.e other fields cannot
+ have commas within them).
+ Comments:
+ Lines in which the first character is either '\n' or '#'
+ are ignored.
+ Header line
+ The header line is the first line in the file, which is
+ always _IGNORED_. It can empty.
+ CPUID is an arch-specific char string, that can be used
+ to identify CPU (and associate it with a set of PMU events
+ it supports). Multiple CPUIDS can point to the same
+ File/path/name.json.
+ Example:
+ CPUID == 'GenuineIntel-6-2E' (on x86).
+ CPUID == '004b0100' (PVR value in Powerpc)
+ Version:
+ is the Version of the mapfile.
+ Dir/path/name:
+ is the pathname to the directory containing the CPU's JSON
+ files, relative to the directory containing the mapfile.csv
+ Type:
+ indicates whether the events or "core" or "uncore" events.
+ Eg:
+ $ grep Silvermont tools/perf/pmu-events/arch/x86/mapfile.csv
+ GenuineIntel-6-37,V13,Silvermont_core,core
+ GenuineIntel-6-4D,V13,Silvermont_core,core
+ GenuineIntel-6-4C,V13,Silvermont_core,core
+ i.e the three CPU models use the JSON files (i.e PMU events) listed
+ in the directory 'tools/perf/pmu-events/arch/x86/Silvermont_core'.