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SubjectRe: [PATCH] perf list: Add s390 support for detailed/verbose pmu event description
On 04/09/2018 01:37 PM, Mark Rutland wrote:
> Hi,
> On Mon, Apr 09, 2018 at 01:00:15PM +0200, Thomas Richter wrote:
>> From: Thomas Richter <>
>> Perf list with flags -d and -v print a description (-d) or
>> a very verbose explanation (-v) of CPU specific counter events.
>> These descriptions are provided with the json files in
>> directory pmu-events/arch/s390/*.json.
>> Display of these descriptions on s390 requires the
>> corresponding json files.
>> On s390 this does not work because function is_pmu_core()
>> does not detect the s390 directory name where the
>> CPU specific events are listed. On x86 it is
>> /sys/bus/event_source/devices/cpu
>> whereas on s390 it is
>> /sys/bus/event_source/devices/cpum_cf
>> /sys/bus/event_source/devices/cpum_sf
>> Fix this by adding s390 directory name testing to
>> function is_pmu_core(). This is the same approach as taken for
>> arm platform.
> I don't think this is quite right.
> On arm, we specifically look for PMU directories which have a
> file called CPUs. e.g.
> /sys/bus/event_source/devices/arm_pmuv3/cpus
> ... where "arm_pmuv3" is the PMU name.
>> diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
>> index 1111d5bf15ca..8675ddf558c6 100644
>> --- a/tools/perf/util/pmu.c
>> +++ b/tools/perf/util/pmu.c
>> @@ -562,6 +562,12 @@ static int is_pmu_core(const char *name)
>> if (stat(path, &st) == 0)
>> return 1;
>> + /* Look for cpu sysfs (specific to s390) */
>> + scnprintf(path, PATH_MAX, "%s/bus/event_source/devices/%s",
>> + sysfs, name);
>> + if (stat(path, &st) == 0)
>> + return 1;
> IIUC here we return true if the PMU has a sysfs directory, but all PMUs
> (including uncore PMUs) should have such a directory, so this will make
> is_pmu_core() always return true.
> Can you match the "cpum_" prefix specifically, instead?
> Thanks,
> Mark.

I am sorry, I don't follow you.
When I look at the code function sequence

+---> pmu_read_sysfs()
This functions scans directory /sys/bus/event_source/devices/
and calls for each entry in this directory. For s390 these entries exist:
cpum_sf cpum_cf tracepoint and software
+---> perf_pmu__find();
+---> pmu_lookup()
+---> pmu_format()
Looks for file /sys/bus/event_source/devices/cpum_cf/format/event
and parses its contents. This returns 0 on s390.
+---> pmu_type()
Looks for file /sys/bus/event_source/devices/cpum_cf/type and
and parses its contents. This returns 0 on s390.
+---> pmu_aliases()
Looks for directory /sys/bus/event_source/devices/cpum_cf/events and
reads out every entry name which is treated as a event name and added
to the list of PMU-Aliases together with the file contents. For example
/sys/bus/event_source/devices/cpum_cf/events/SF_CYCLES_BASIC with the
file contents event=0xb0000. This is the raw event number.
+----> pmu_aliases_parse() + perf_pmu__new_alias()
Check and add alias name to a list.
+---> pmu_cpumask()
This tests for files /sys/bus/event_source/devices/cpum_cf/cpus or
/sys/bus/event_source/devices/cpum_cf/cpumask which do not exist on
+---> pmu_add_cpu_aliases() adds the list of aliases such as cpum_sf/SF_CYCLES_BASIC/
to the global list of aliases. But ths happens only when
+---> is_pmu_core()
function returns true.
And for s390 it needs to test for /sys/bus/event_source/devices/cpum_sf/ and
These directories are used to read the alias names in function
pmu_aliases() above.

Maybe I misunderstand this whole scheme, but with this patch the perf list commands works...

Thomas Richter, Dept 3303, IBM LTC Boeblingen Germany
Vorsitzende des Aufsichtsrats: Martina Koederitz
Geschäftsführung: Dirk Wittkopp
Sitz der Gesellschaft: Böblingen / Registergericht: Amtsgericht Stuttgart, HRB 243294

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