Re: [PATCH v1 0/3] Metric related performance improvements

[Arnaldo Carvalho de Melo <acme@kernel.org>]

On Wed, Apr 09, 2025 at 11:49:16PM -0700, Namhyung Kim wrote:
> Hi Ian,
> 
> On Wed, Apr 09, 2025 at 09:45:29PM -0700, Ian Rogers wrote:
> > The "PMU JSON event tests" have been running slowly, these changes
> > target improving them with an improvement of the test running 8 to 10
> > times faster.
> > 
> > The first patch changes from searching through all aliases by name in
> > a list to using a hashmap. Doing a fast hashmap__find means testing
> > for having an event needn't load from disk if an event is already
> > present.
> > 
> > The second patch switch the fncache to use a hashmap rather than its
> > own hashmap with a limited number of buckets. When there are many
> > filename queries, such as with a test, there are many collisions with
> > the previous fncache approach leading to linear searching of the
> > entries.
> > 
> > The final patch adds a find function for metrics. Normally metrics can
> > match by name and group, however, only name matching happens when one
> > metric refers to another. As we test every "id" in a metric to see if
> > it is a metric, the find function can dominate performance as it
> > linearly searches all metrics. Add a find function for the metrics
> > table so that a metric can be found by name with a binary search.
> > 
> > Before these changes:
> > ```
> > $ time perf test -v 10
> >  10: PMU JSON event tests                                            :
> >  10.1: PMU event table sanity                                        : Ok
> >  10.2: PMU event map aliases                                         : Ok
> >  10.3: Parsing of PMU event table metrics                            : Ok
> >  10.4: Parsing of PMU event table metrics with fake PMUs             : Ok
> >  10.5: Parsing of metric thresholds with fake PMUs                   : Ok
> > 
> > real    0m18.499s
> > user    0m18.150s
> > sys     0m3.273s
> > ```
> > 
> > After these changes:
> > ```
> > $ time perf test -v 10
> >  10: PMU JSON event tests                                            :
> >  10.1: PMU event table sanity                                        : Ok
> >  10.2: PMU event map aliases                                         : Ok
> >  10.3: Parsing of PMU event table metrics                            : Ok
> >  10.4: Parsing of PMU event table metrics with fake PMUs             : Ok
> >  10.5: Parsing of metric thresholds with fake PMUs                   : Ok
> > 
> > real    0m2.338s
> > user    0m1.797s
> > sys     0m2.186s
> > ```
> 
> Great, I also see the speedup on my machine from 32s to 3s.
> 
> Tested-by: Namhyung Kim <namhyung@kernel.org>

I'm collecting this for v2 as well, ok? Holler if you disagree.

- Arnaldo