I've posted this online now -- https://internals.rust-lang.org/t/plan-to-test-parallel-rustc/11487
we can discuss feedback here if there is any! (or on thread if it's more appropriate)
one thing that I'm thinking of are potential clippy, miri and things like that breakages that if you have those and try to do rustup update you may not escape for a while from the parallel version that was built
I think that's ok anyway ...
I guess plausibly downstream toolstate might die pretty badly
though I'm not sure how
not sure if we can test that in advance? i.e., if clippy does something not thread safe?
(do standard PR builds or try builds test tools?)
just in case, I was referring to the time window between the nightly with parallel enabled goes out and the next nightly version
if between those a change that breaks miri, clippy or any of the other components lands
you may not escape the parallel nightly for a while unless you do something
but just a
rustup update won't allow you to update because next versions will have a broken component
the advantage to doing it this week is that all tools must build (modulo miri)
since it's beta week
Have you checked that parallel compiler passes tests? I know there was one test where the single thread compiler outputs an extra cycle error.
hm, we're seeing the opposite
i.e., one less cycle failure with parallel
That sounds like the same thing =P
oh I completely missed the "single threaded" bit
Seems like a concern :)
@simulacrum I assume you've got a method in mind of how to land that while making sure the previous PR makes its way into nightlie?
we're less than 4 hours out from nightly "fork" and the rollup won't start testing for at least an hour or two, so it's pretty much guaranteed that everything sync up appropriately
@nikomatsakis It could just be that the parallel compiler chooses to break the cycle in a location it can't be recovered from. Recovering from cycles is really questionable in general and it's probably not something we should do.
anyway I don't think it has to block doing some experiments w/ nightly
but we should file an issue to investigate or something at least?
yeah I think an issue would be good
I've posted a dedicated thread -- https://internals.rust-lang.org/t/help-test-parallel-rustc/11503 -- for gathing measurements now
@simulacrum I see the revert already landed, thanks for managing that!
Yep tonight's nightly should be back to normal
I was wondering what rayon did we ship the parallel version with
it seems like it was master's
didn't we want to use Niko's fork?
we intentionally decided not to I think
since it's pretty alpha-level