Re: [PATCH v2 4/4] Bump rename limit defaults (yet again)

On Wed, Jul 14, 2021 at 01:12:33AM +0000, Elijah Newren via GitGitGadget wrote:

The combined effect of the above is that the file size used in past
calculations was likely about 5x too large.  Combine that with a CPU
performance improvement of ~30%, and we can increase the limits by
a factor of sqrt(5/(1-.3)) = 2.67, while keeping the original stated
time limits.

It's slightly sad that we only got a 30% CPU improvement in the past 10
years. Are you just counting clock speed as a short-hand here? I think
that doesn't tell the whole story. But all of this is a side-note
anyway.  What I care about is your actual timings. :)

(It also seems like this rename detection is ripe for parallelization,
 but obviously that's a totally separate topic).

Using the original time limit of 2s for diff.renameLimit, and bumping
merge.renameLimit from 10s to 60s, I found the following timings using
the simple script at the end of this commit message (on an AWS c5.xlarge
which reports as "Intel(R) Xeon(R) Platinum 8124M CPU @ 3.00GHz"):

      N   Timing
   1300    1.995s
   7100   59.973s

So let's round down to nice even numbers and bump the limits from
400->1000, and from 1000->7000.

Sounds good. Thanks for thoroughly measuring and updating.

-Peff