Review Request: 8004352: build-infra: Limit JOBS on large machines

[Mike Duigou]

A couple of comments;

- Can you reverse steps #2 and #3? Having the hard cap last makes more sense.

- In JDK-8007327 I requested some memory size definitions such as MEMORY_SIZE_NORMAL_HEAP for sizing of JVM heaps. The explicit "1000" should probably be replaced with the MEMORY_SIZE_NORMAL_HEAP constant. Elsewhere the value is "1100".

- The CONCURRENT_BUILD_JOBS is no longer JOBS * 2. Do we think that's right?

Mike

On Feb 15 2013, at 04:06 , Erik Joelsson wrote:

> The current default for number of parallel build jobs is just equal to the number of cores in the system. While this works well on many machines, there have been several reports of this not working. I have been trying to come up with a better scheme for the default and the following is something that I think will do. It has been active in the build-infra forest for a while now.
> 
> The complaints that were raised were usually concerning one of the following:
> 
> * A big machine with very many cpus didn't scale well when using all of them, so there is no point in trying to, it just made the build less stable. Suggestion, introduce a hard cap.
> * A machine with lots of cpus but not as much memory would run out of memory. Suggestion, limit number of jobs on memory as well as cpus.
> * The build eats up all my resources, leaving my browser unusable. Suggestion, don't use everything unless asked for.
> 
> So this is what I ended up with:
> 1. Take the min of num_cores and memory_size/1000
> 2. Cap at 16
> 3. If more than 4 cores, shave it to 90% rounded down to leave some room.
> 
> The user can still override this in two ways. Either by using any of the configure arguments:
> 
>  --with-num-cores        number of cores in the build system, e.g.
>                          --with-num-cores=8 [probed]
>  --with-memory-size      memory (in MB) available in the build system, e.g.
>                          --with-memory-size=1024 [probed]
>  --with-jobs             number of parallel jobs to let make run [calculated
>                          based on cores and memory]
> 
> Or by setting JOBS=<number> on the make command line.
> 
> Also not that this change will set the CONCURRENT_BUILD_JOBS for hotspot to the value of JOBS so that it too will be overridden by the above.
> 
> http://cr.openjdk.java.net/~erikj/8004352/webrev.root.01/
> 
> /Erik