Review Request: 8004352: build-infra: Limit JOBS on large machines (original) (raw)

Erik Joelsson erik.joelsson at oracle.com
Mon Feb 18 11:19:03 UTC 2013

On 2013-02-15 18:12, Mike Duigou wrote:

A couple of comments;

- Can you reverse steps #2 and #3? Having the hard cap last makes more sense. I agree and will do. - In JDK-8007327 I requested some memory size definitions such as MEMORYSIZENORMALHEAP for sizing of JVM heaps. The explicit "1000" should probably be replaced with the MEMORYSIZENORMALHEAP constant. Elsewhere the value is "1100". I can't find any other reference to this constant, but I can certainly change it to 1100. I just wanted something lower than 1024 since the reported amount of memory in a machine is usually somewhat lower than the exact multiple of 2 and the division is rounded down. - The CONCURRENTBUILDJOBS is no longer JOBS * 2. Do we think that's right? I think it's correct that you can squeeze out a bit more performance from the hotspot (or jdk native) build by using cores * 2 as number of jobs, but any value higher than cores will affect the third bullet point below (don't interfere with my browser experience while I'm building). I also found it weird to have a different setting for hotspot and the jdk native build and thought this a good opportunity to unify the settings.

The problem is that if someone increases JOBS to cores * 2 for maximum speed, there will most likely be problems in the java source generation in the jdk, which is more memory intensive. My assumption is that the speed loss from cores * 2 to cores * 1 is small enough to not matter much.

We could fix this, but I'm not sure it's worth the effort. The user just wants to say something like, "go full speed while I make coffee", "leave some room so my terminal doesn't lock up" or "I'm running 4 builds in parallel, tune it down please". This could be expressed as a percentage, with a suitable default. For each part of the build, where we make a submake call, we can add a call to calculate a suitable value for the -j flag. Input is a factor indicating memory to cpu requirements, the factor from the user (set at configure or at make invocation), the number of cpus (from configure) and the amount of memory (from configure).

/Erik

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 numcores and memorysize/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= on the make command line. Also not that this change will set the CONCURRENTBUILDJOBS 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

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