[PATCH] D23755: [cmake] Use separate doctrees to prevent races between Sphinx instances

[Michał Górny via llvm-commits]

mgorny added a comment.

In https://reviews.llvm.org/D23755#559296, @beanz wrote:

> In https://reviews.llvm.org/D23755#558390, @mgorny wrote:
>
> > Tell that to the person who is running Gentoo on old x86. Because most of binary distros don't even work on CPU that old ;-).
>
>
> I care very little about minor impacts on downstream consumers of source distributions. I care way more about people who are building LLVM regularly because it impacts us every day. Further, I very strongly believe that we need to build our software thinking about the future, and MP is the present, and the future. Single core CPUs are becoming less and less common every day. Optimizing for them doesn't seem prudent to me.


I'm more concerned about processing the same data multiple times while we have an opportunity to do it once and cache the result. While I can agree that my original method was hacky, it seemed to provide the best performance for everyone.

Anyway, I don't think we're going to reach an agreement here, so I've updated the patch to safely run Sphinx in parallel like you last requested (I think). In most of the cases, the performance won't change, only now two doctrees will be created rather than one being created and then overwritten.


https://reviews.llvm.org/D23755