Re: [PATCH v3] perf jevents: Parse metrics during conversion

[John Garry]

On 05/12/2022 12:53, Arnaldo Carvalho de Melo wrote:
> Em Wed, Nov 30, 2022 at 07:41:38PM -0800, Ian Rogers escreveu:
> > Currently the 'MetricExpr' json value is passed from the json
> > file to the pmu-events.c. This change introduces an expression
> > tree that is parsed into. The parsing is done largely by using
> > operator overloading and python's 'eval' function. Two advantages
> > in doing this are:
> >
> > 1) Broken metrics fail at compile time rather than relying on
> >     `perf test` to detect. `perf test` remains relevant for checking
> >     event encoding and actual metric use.
> >
> > 2) The conversion to a string from the tree can minimize the metric's
> >     string size, for example, preferring 1e6 over 1000000, avoiding
> >     multiplication by 1 and removing unnecessary whitespace. On x86
> >     this reduces the string size by 3,050bytes (0.07%).
> >
> > In future changes it would be possible to programmatically
> > generate the json expressions (a single line of text and so a
> > pain to write manually) for an architecture using the expression
> > tree. This could avoid copy-pasting metrics for all architecture
> > variants.
> >
> > Signed-off-by: Ian Rogers<irogers@xxxxxxxxxx>
> >
> > v3. Avoids generic types on standard types like set that aren't
> >      supported until Python 3.9, fixing an issue with Python 3.6
> >      reported-by John Garry. v3 also fixes minor pylint issues and adds
> >      a call to Simplify on the read expression tree.
> Cool, John looked reviewed it (may I add the tag?). Applying to my local
> tree, will do some light testing.

Actually I just got as far as testing v2 (which gave rise to this v3). I 
will look at it further today.

Thanks,
John