Describe how to trigger perf runs

[lqd]

This PR adds the command to request perf runs on PRs.

Fixes #1236

[JohnTitor]

I'm not sure if the profiling chapter is the best place to describe in details. We have https://rustc-dev-guide.rust-lang.org/getting-started.html#performance and it would be a better one, I think. And I feel like that it's more of instruction for team members rather than (new) contributors so forge or something else would be better, though it's probably fine to mention here.

[spastorino]

I'm unsure about the getting started section, maybe it can go there too but as I was reading the place where @lqd has placed this it made sense to me because it was already referring to running perf with the bot, it's just that @lqd was explicit about how to run it.

[lqd]

Right, this page already mentioned the old bot, and why it seemed an appropriate one.

[JohnTitor]

Uhm, indeed the getting started is not something that team members (i.e. someone has the r+ right) read usually. But I still feel like the profiling chapter is a bit too specific to mention the general bot usage in detail and I don't expect anyone can find that information.

[spastorino]

I think we should split this discussion into two. On one side maybe we need to restructure some stuff to properly fit what @JohnTitor is saying on the other side I think this PR is already a simple improvement given first, that we don't have this information anywhere in the guide, and that the section is already mentioning it. The other option is to make a very minimal change, like ...

• The rustc-perf project makes this easy and can be triggered to run on a PR via the @rust-timer bot with @bors try @rust-timer queue.

[camelid]

rustc-perf has a help page that we could consider linking to: https://perf.rust-lang.org/help.html

[JohnTitor]

Ah, makes sense, restructuring can be later 👍 I'm fine with the current or the link @camelid provided.

[jyn514]

And I feel like that it's more of instruction for team members rather than (new) contributors so forge or something else would be better

There are already quite a lot of docs that aren't meant for new contributors, I'm not sure how that's related to it being on forge or not. Most of the profiling section is for existing contributors.

[JohnTitor]

There are already quite a lot of docs that aren't meant for new contributors, I'm not sure how that's related to it being on forge or not. Most of the profiling section is for existing contributors.

I mean, perf-run requires a try right on rust-lang/rust so it's not for existing contributors but team members.

[spastorino]

I'm fine with the current state of this, would leave the final decision to someone else :).

[JohnTitor]

👍, let's go ahead, thanks!