linux-kernel - Re: [PATCH RFC 4/7] perf pmu: Rename uncore symbols to include system PMUs

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Message-ID: <fac99c40-dace-3e2e-c8f4-b2afed8b7c61@huawei.com>
Date:   Mon, 10 Feb 2020 15:44:48 +0000
From:   John Garry <john.garry@...wei.com>
To:     Jiri Olsa <jolsa@...hat.com>
CC:     <peterz@...radead.org>, <mingo@...hat.com>, <acme@...nel.org>,
        <mark.rutland@....com>, <alexander.shishkin@...ux.intel.com>,
        <namhyung@...nel.org>, <will@...nel.org>, <ak@...ux.intel.com>,
        <linuxarm@...wei.com>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <suzuki.poulose@....com>,
        <james.clark@....com>, <zhangshaokun@...ilicon.com>,
        <robin.murphy@....com>
Subject: Re: [PATCH RFC 4/7] perf pmu: Rename uncore symbols to include system
 PMUs

On 10/02/2020 12:07, Jiri Olsa wrote:
> On Fri, Jan 24, 2020 at 10:35:02PM +0800, John Garry wrote:
> 
> SNIP
> 
>>   		/* Only split the uncore group which members use alias */
>> -		if (!evsel->use_uncore_alias)
>> +		if (!evsel->use_uncore_or_system_alias)
>>   			goto out;
>>   
>>   		/* The events must be from the same uncore block */
>> diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
>> index 8b99fd312aae..569aba4cec89 100644
>> --- a/tools/perf/util/pmu.c
>> +++ b/tools/perf/util/pmu.c
>> @@ -623,7 +623,7 @@ static struct perf_cpu_map *pmu_cpumask(const char *name)
>>   	return NULL;
>>   }
>>   
>> -static bool pmu_is_uncore(const char *name)
>> +static bool pmu_is_uncore_or_sys(const char *name)
> 

Hi jirka,

> so we detect uncore PMU by checking for cpumask file
> 

For PMUs which could be considered "system" PMUs, they also have a 
cpumask, like the PMU I use as motivation for this series:

root@(none)$ pwd
/sys/bus/event_source/devices/smmuv3_pmcg_100020
root@(none)$ ls -l
total 0
-r--r--r--    1 root     root          4096 Feb 10 14:50 cpumask
drwxr-xr-x    2 root     root             0 Feb 10 14:50 events
drwxr-xr-x    2 root     root             0 Feb 10 14:50 format
-rw-r--r--    1 root     root          4096 Feb 10 14:50 
perf_event_mux_interval_ms
drwxr-xr-x    2 root     root             0 Feb 10 14:50 power
lrwxrwxrwx    1 root     root             0 Feb 10 14:50 subsystem -> 
../../bus/event_source
-r--r--r--    1 root     root          4096 Feb 10 14:50 type
-rw-r--r--    1 root     root          4096 Feb 10 14:50 uevent


Other PMU drivers which I have checked in drivers/perf also have the same.

Indeed I see no way to differentiate whether a PMU is an uncore or 
system. So that is why I change the name to cover both. Maybe there is a 
better name than the verbose pmu_is_uncore_or_sys().

> I don't see the connection here with the sysid or '_sys' checking,
> that's just telling which ID to use when looking for an alias, no?

So the connection is that in perf_pmu__find_map(), for a given PMU, the 
matching is now extended from only core or uncore PMUs to also these 
system PMUs. And I use the sysid to find an aliasing table for any 
system PMUs present.

> shouldn't that be separated?

Yes, I now think that this would be a better option. So currently I am 
combining it and it causes a problem, like I have noted in patch #5:

struct pmu_events_map *perf_pmu__find_map(struct perf_pmu *pmu)
{
[SNIP]
	sysid = perf_pmu__getsysid();

   /*
   * Match sysid as first perference for uncore/sys PMUs.
   *
   * x86 uncore events match by cpuid, but we would not have 	map->socid
* set for that arch (so any matching here would fail for that).
*/
if (pmu && pmu_is_uncore_or_sys(pmu->name) &&
    !is_arm_pmu_core(pmu->name) && sysid) {


Thanks,
John