GHC Performance Tsar

Ryan Newton rrnewton at
Thu Dec 6 15:50:40 CET 2012

I'm particularly interested in parallel performance in the >8 core space.
 (In fact, we saw some regressions from 7.2->7.4 that we never tracked down
properly, but maybe can now.)

If the buildbot can make it easy to add a new "slave" machine that runs and
uploads its result to a central location, then I would be happy to donate a
few hours of dedicated time (no other logins) on a 32 core westmere
machine, and hopefully other architectures soon.

Maybe, this use case is well-covered by creating a jenkins/travis slave and
letting it move the data around?  (CodeSpeed looks pretty nice too.)


On Wed, Dec 5, 2012 at 12:40 AM, Ben Lippmeier <benl at> wrote:

> On 01/12/2012, at 1:42 AM, Simon Peyton-Jones wrote:
> > | > While writing a new nofib benchmark today I found myself wondering
> > | > whether all the nofib benchmarks are run just before each release,
> >
> > I think we could do with a GHC Performance Tsar.  Especially now that
> Simon has changed jobs, we need to try even harder to broaden the base of
> people who help with GHC.  It would be amazing to have someone who was
> willing to:
> >
> > * Run nofib benchmarks regularly, and publish the results
> >
> > * Keep baseline figures for GHC 7.6, 7.4, etc so we can keep
> >   track of regressions
> >
> > * Investigate regressions to see where they come from; ideally
> >   propose fixes.
> >
> > * Extend nofib to contain more representative programs (as Johan is
> >   currently doing).
> >
> > That would help keep us on the straight and narrow.
> I was running a performance regression buildbot for a while a year ago,
> but gave it up because I didn't have time to chase down the breakages. At
> the time we were primarily worried about the asymptotic performance of DPH,
> and fretting about a few percent absolute performance was too much of a
> distraction.
> However: if someone wants to pick this up then they may get some use out
> of the code I wrote for it. The dph-buildbot package in the DPH repository
> should still compile. This package uses
> which includes code
> for running tests, collecting the timings, comparing against a baseline,
> making pretty reports etc. There is then a second package buildbox-tools
> which has a command line tool for listing the benchmarks that have deviated
> from the baseline by a particular amount.
> Here is an example of a report that dph-buildbot made:
> Ben.
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