Re: [PATCH RFC 5/7] perf pmu: Support matching by sysid

[John Garry]

On 11/02/2020 13:47, Jiri Olsa wrote:

Hi Jirka,

> > > > +
> > > > +	return buf;
> > > > +}
> > > > +
> >
> > I have another series to add kernel support for a system identifier sysfs
> > entry, which I sent after this series:
> >
> > https://lore.kernel.org/linux-acpi/1580210059-199540-1-git-send-email-john.garry@xxxxxxxxxx/
> >
> > It is different to what I am relying on here - it uses a kernel soc driver
> > for firmware ACPI PPTT identifier. Progress is somewhat blocked at the
> > moment however and I may have to use a different method:
> >
> > https://lore.kernel.org/linux-acpi/20200128123415.GB36168@bogus/
>
> I'll try to check ;-)

Summary is that there exists an ACPI firmware field which we could 
expose to userspace via sysfs - this would provide the system id. 
However there is a proposal to deprecate it in the ACPI standard and, as 
such, would prefer that we don't add kernel support for it at this stage.

So I am evaluating the alternative in the meantime, which again is some 
firmware method which should allow us to expose a system id to userspace 
via sysfs. Unfortunately this is arm specific. However, other archs can 
still provide their own method, maybe a soc driver:

Documentation/ABI/testing/sysfs-devices-soc#n15

> > > > +static char *perf_pmu__getsysid(void)
> > > > +{
> > > > +	char *sysid;
> > > > +	static bool printed;
> > > > +
> > > > +	sysid = getenv("PERF_SYSID");
> > > > +	if (sysid)
> > > > +		sysid = strdup(sysid);
> > > > +
> > > > +	if (!sysid)
> > > > +		sysid = get_sysid_str();
> > > > +	if (!sysid)
> > > > +		return NULL;
> > > > +
> > > > +	if (!printed) {
> > > > +		pr_debug("Using SYSID %s\n", sysid);
> > > > +		printed = true;
> > > > +	}
> > > > +	return sysid;
> > > > +}
> > >
> > > this part is getting complicated and AFAIK we have no tests for it
> > >
> > > if you could think of any tests that'd be great.. Perhaps we could
> > > load 'our' json test files and check appropriate events/aliasses
> > > via in pmu object.. or via parse_events interface.. those test aliases
> > > would have to be part of perf, but we have tests compiled in anyway
> >
> > Sorry, I don't fully follow.
> >
> > Are you suggesting that we could load the specific JSONs tables for a system
> > from the host filesystem?
>
> I wish to see some test for all this.. I can only think about having
> 'test' json files compiled with perf and 'perf test' that looks them
> up and checks that all is in the proper place

OK, let me consider this part for perf test support.

Thanks,
John