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
