Re: [PATCH v5 5/6] p5310-pack-bitmaps.sh: enable `pack.writeReverseIndex`

[Taylor Blau <me@ttaylorr.com>]

On Wed, Jul 20, 2022 at 06:38:23PM +0000, Abhradeep Chakraborty via GitGitGadget wrote:
> From: Abhradeep Chakraborty <chakrabortyabhradeep79@gmail.com>
>
> Enable `pack.writeReverseIndex` before running pack-bitmap related
> performance tests.
>
> The performance difference with `pack.writeReverseIndex` enabled and
> with disabled are given below -

Thanks; this order of changes in the t/perf suite makes sense to me. One
note, this sort of change where we're comparing all of the tests in a
single t/perf file against themselves before and after some change, it
is helpful to do (in t/perf)

  ./run HEAD . p5310-pack-bitmaps.sh

which compares HEAD to what's in the current tree. You'll get the
results side-by-side, which makes them a little easier to scan. You can
also aggregate results together from multiple runs with the
t/perf/aggregate.perl script.

One gotcha (that has often bitten me in the past) is that when running
the perf suite with `.` as your build target, it uses whatever git
binary is sitting in your tree. So make sure that it is both (a)
up-to-date, ie., that it is the result of compiling what's currently in
your tree, and (b) that it is compiled with the same settings as what
you built HEAD with.

I have often scratched my head at why the result of running some perf
suite on '.' seems much slower than it should be, only to realize that
the "git" binary sitting in my tree was built with -O0 or something.

Thanks,
Taylor