Re: [PATCH] git-download: Speed up 'git-predicate'.

[Ludovic Courtès]

Hi Christopher,

Christopher Baines <address@hidden> skribis:

> Running the current implementation of git-predicate on the guix
> repository with 50 trials takes:
>
>   real    0m5.374s
>   user    0m4.052s
>   sys     0m1.484s
>
> Compared to the following for the patched implementation:
>
>   real    0m8.398s
>   user    0m5.040s
>   sys     0m2.016s
>
> This shows that the patched implementation has decreased the
> performance. Using the real value, the test time has increased by ~3
> seconds. This corresponds roughly to a change from ~0.11 seconds
> previously, to ~0.17 seconds for each individual traversal of the entire
> repository.
>
> I encountered a performance issue when trying to use git-predicate with
> this repository [2], which I have written a Guix package for here [3].
> Instead of the 1463 files that git ls-files reports locally for the guix
> repository, smart-answers contains 26732 files.
>
> The running time with smart-answers is left as an exercise to the
> reader, all I can say is that on my machine, it takes more than 40
> minutes for just 1 trial.
>
> Using this patch, running the test script with 1 trial gives:
>
>   real    0m4.917s
>   user    0m3.640s
>   sys     0m1.428s

So in short, the new implementation is 100 times faster on large repos
but roughly the same or slightly slower on smaller repos, right?

Thanks for fixing this!

Ludo’.