On 19/09/2013 7:43 AM, Pete Brunet wrote:
If a machine has 4 cores and 8 threads will the jdk8 build run faster
than one with 4 cores and 4 threads?
All depends on where the bottlenecks are. Given a build is pretty much
I/O bound I wouldn't expect much difference.
If so would it be a 2x decrease in build time?
No. The CPU component of the build will be a fraction of the I/O component.
Even a compute bound task won't see a 2x difference when run on twice
the number of hardware threads as they share physical resources in the
core so can't completely run in parallel.
> Would the build explicitly take advantage of the
hyper-threading or would any increase in performance be a side effect?
The build like most other software on the system knows nothing about
processors, cores and (hyper)-threads. The OS presents a model where all
of those things represent logical processors and it runs native threads
on each logical.
Trying to do too much in parallel can easily degrade performance - you
need to understand how Amdahls Law applies to the computation you are doing.
David
