Re: [PATCHv4 00/19] perf metric: Add support to reuse metric

From: Jiri Olsa
Date: Mon Aug 03 2020 - 12:26:51 EST


On Mon, Aug 03, 2020 at 08:54:16AM -0700, Ian Rogers wrote:
> On Sat, Aug 1, 2020 at 4:41 AM Paul A. Clarke <pc@xxxxxxxxxx> wrote:
> >
> > On Wed, Jul 29, 2020 at 11:18:49AM +0200, Jiri Olsa wrote:
> > > this patchset is adding the support to reused metric in
> > > another metric.
> > >
> > > For example, to define IPC by using CPI with change like:
> > >
> > > {
> > > "BriefDescription": "Instructions Per Cycle (per Logical Processor)",
> > > - "MetricExpr": "INST_RETIRED.ANY / CPU_CLK_UNHALTED.THREAD",
> > > + "MetricExpr": "1/CPI",
> > > "MetricGroup": "TopDownL1",
> > > "MetricName": "IPC"
> > > },
> > >
> > > I won't be able to find all the possible places we could
> > > use this at, so I wonder you guys (who was asking for this)
> > > would try it and come up with comments if there's something
> > > missing or we could already use it at some places.
> > >
> > > It's based on Arnaldo's tmp.perf/core.
> > >
> > > v4 changes:
> > > - removed acks from patch because it changed a bit
> > > with the last fixes:
> > > perf metric: Collect referenced metrics in struct metric_ref_node
> > > - fixed runtime metrics [Kajol Jain]
> > > - increased recursion depth [Paul A. Clarke]
> > > - changed patches due to dependencies:
> > > perf metric: Collect referenced metrics in struct metric_ref_node
> > > perf metric: Add recursion check when processing nested metrics
> > > perf metric: Rename struct egroup to metric
> > > perf metric: Rename group_list to metric_list
> > >
> > > Also available in here:
> > > git://git.kernel.org/pub/scm/linux/kernel/git/jolsa/perf.git
> > > perf/metric
> >
> > I built and ran from the above git branch, and things seem to work.
> > Indeed, I was able to apply my changes to exploit the new capabilities
> > via modifications to tools/perf/pmu-events/arch/powerpc/power9/metrics.json,
> > as I posted earlier (and will submit once this set gets merged).
> >
> > Tested-by: Paul A. Clarke <pc@xxxxxxxxxx>
> >
> > One thing I noted, but which also occurs without these patches, is that
> > the perf metrics are not computed unless run as root:
> > --
> > $ perf stat --metrics br_misprediction_percent command
> >
> > Performance counter stats for 'command':
> >
> > 1,823,530,051 pm_br_pred:u
> > 2,662,705 pm_br_mpred_cmpl:u

it's because when you don't run as root, events will get the :u suffix,
so they will not match the events in metric.. we need to decide if we
want the metric to match events without modifiers or be strict about it

> >
> > $ /usr/bin/sudo perf stat --metrics br_misprediction_percent command
> >
> > Performance counter stats for 'command':
> >
> > 1,824,655,269 pm_br_pred # 0.09 br_misprediction_percent
> > 1,654,466 pm_br_mpred_cmpl
> > --
> >
> > Is that expected? I don't think it's always been that way.
>
> I agree Paul, this seems broken. I've noticed a bunch of issues with
> printing CSV, per-socket output and so on. Jiri may have a better idea
> but I plan to look at problems in this area later, and hopefully stick
> a few tests on it :-)

ok, that'd be great, thanks

jirka