Description of the problem / feature request:

My project uses multithreaded code emitters written in Java. They may eat CPU and RAM, and when running concurrently may overwhelm the build host. It'd be great if I could somehow signal to Bazel's scheduler that these processes are heavier so that it could adjust accordingly.

Feature requests: what underlying problem are you trying to solve with this feature?

When porting a project from Maven to Bazel, I observe longer build times with Bazel. Looking at the critical path, I see that a few actions--most notably one of the code emitters--takes significantly longer under Bazel (23s) than when run from the command line (15s) or Maven.

If I understand the code correctly (GenRuleAction.java), Bazel treats all genrules the same. They're assumed to consume ~300M of RAM and a single CPU. My tasks, however, typically occupy 2-4 CPUs, so I'd like Bazel to take this into account when scheduling actions running on my build host.

I'm still too new to Bazel to suggest a concrete API, but maybe something like

genrule(
    ...,
    resources=(512, 3.0, 0.0),  # Corresponds to ResourceSet: 512M, 3 CPUs, 0/default for I/O
)

# or

genrule(
    ...,
    resources_ram=512,
    resources_cpu=3.0,
)    

would be feasible? (Ditto for plain rules, too!)

What operating system are you running Bazel on?

Linux (CentOS 6.6)

What's the output of bazel info release?

$ bazel info release
release 0.16.1- (@non-git)

(This is 0.18.0rc8.)

If bazel info release returns "development version" or "(@Non-Git)", tell us how you built Bazel.

n/a. This is just a feature request.

What's the output of git remote get-url origin ; git rev-parse master ; git rev-parse HEAD ?

n/a. This is just a feature request.

Have you found anything relevant by searching the web?

#988 touches on a similar topic.

Any other information, logs, or outputs that you want to share?