DMD performance dashboard is live now

[Abul Hossain Khan]

> Congratz, nice work. Is there any plan to eventually block a PR 
> if the delta is too suspiciously positive ?

Thank you so much, I don't think blocking makes sense, because a 
new feature implementation can cost some performance

> that someone could look at it with fresh eyes and not need to 
> go to the Info page

Good point, I'll add axis labels and more clearer titles

> It might also be interesting to integrate something like this 
> into it (just for D)

Looks interesting, I'll have a look at it.

> I see some graphs are a bit noisy.

Yeah, those are wall time and peak RSS. The main metrics are 
instruction counts from cachegrind, which barely move between 
runs (around 0.001%). Wall time is noisy on shared runners 
however many times you run it, so it's more informational.

> I would suggest moving the benchmarks to a dedicated server

Yes, it runs on GitHub Actions, and that's the reason the main 
metric is instruction count and not time. A dedicated server 
would be really great for this, but that would be up to the 
Organisation DLF.

> are you pinning the Phobos version?

No we are not, I had suggested pinning it before, but Dennis 
pointed out that an old pinned Phobos has a large maintenance 
cost, since dmd and Phobos kinda change together. What we can do 
is store the Phobos commit in each record, so if a chart jumps 
because of Phobos, everyone can see it.

Thank you so much everyone for the suggestion, Really Appreciated!