Recommend reducing runfiles tree creation

[ulfjack]

Problem

We have a build that is slow due to excessive local runfiles tree creation, while most actions are cached (or executed) remotely and do not need a runfiles tree. Enabling --nobuild_runfiles_links can reduce the time of such builds by a factor of 2 or more.

I attached before/after screenshots that show the effect of setting this flag. In this build, we still see an excessive amount of "acquiring semaphore" operations locally, but at least it is significantly faster.

Before

After

[ulfjack]

Posting two internal invocation ids as a reminder if we need more details:

• before: 03879072-f1e6-4770-a392-9dc0c5fc1173
• after: 2a542e2b-cf26-4219-8a0d-a3feef010719

[ulfjack]

Also see https://github.com/bazelbuild/bazel/issues/6627 for more details on runfiles trees.