On Apr 3, 2013, at 23:44, Joern Rennecke <joern.renne...@embecosm.com> wrote:
> How does that work? > The binaries have to get the all the machines of the clusters somewhere. > Does this assume you are using NFS or similar for your build directory? > Won't the overhead of using that instead of local disk kill most of the > parallelization benefit of a cluster over a single SMP machine? This will be true regardless of communication method. There is so little opportunity for parallelism that anything more than 4-8 local cores is pretty much wasted. On a 4-core machine, more than 50% of the wall time is spent on things that will not use more than those 4 cores regardless. If the other 40-50% or so can be cut by a factor 4 compared to 4-core execution, we still are talking about at most a 30% improvement on the total wall time. Even a small serial overhead for communicating sources and binaries will still reduce this 30%. We need to improve the Makefiles before it makes sense to use more parallelism. Otherwise we'll just keep running into Amdahl's law. -Geert
