Subject: Re: [PATCH v21 15/19] perf, tools: Add README for info on parsing JSON/map files

From: Arnaldo Carvalho de Melo <[email-masked]>
Date: Mon, 3 Oct 2016 21:38:10 -0300

Em Thu, Sep 15, 2016 at 03:24:52PM -0700, Sukadev Bhattiprolu escreveu:
> Signed-off-by: Sukadev Bhattiprolu <[email-masked]>
> Acked-by: Jiri Olsa <[email-masked]>
> Acked-by: Ingo Molnar <[email-masked]>
> ---
> Changelog[v21]
> 	- Update README to reflect the Topics.json directory tree layout.

Fixed this:

[acme@jouet linux]$ am /wb/1.patch 
Applying: perf, tools: Add README for info on parsing JSON/map files
.git/rebase-apply/patch:162: new blank line at EOF.
+
warning: 1 line adds whitespace errors.
tools/perf/pmu-events/README:148: new blank line at EOF.
[acme@jouet linux]$

> ---
>  tools/perf/pmu-events/README | 148 +++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 148 insertions(+)
>  create mode 100644 tools/perf/pmu-events/README
> 
> diff --git a/tools/perf/pmu-events/README b/tools/perf/pmu-events/README
> new file mode 100644
> index 0000000..c5ee208e
> --- /dev/null
> +++ b/tools/perf/pmu-events/README
> @@ -0,0 +1,148 @@
> +
> +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.
> +
> +NOTES:
> +	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
> +
> +where:
> +
> +	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:
> +		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'.
> +
> -- 
> 1.8.3.1