Hello,
When I implemented the heuristic to choose a suitable default
concurrency, I only ever worried about the build. I think having tests
use the same concurrency setting must be a new feature? In any case, it
seems like there is a case for reducing concurrency when running tests.
Another note. It at least used to be quite tricky to get correct
information about cores vs hyperthreading from the OS. I know today we
aren't even consistent with this across platforms. Perhaps we should
revisit this heuristic and take hyperthreading into consideration too.
The current implemenation uses 100% of number of virtual cpus when 1 to
4 of them, then 90% at 5 to 16. After that it caps out at 16. (I might
remember some detail wrong here)
/Erik
On 2015-09-14 04:10, Maurizio Cimadamore wrote:
The information I posted was slightly incorrect, sorry - my machine
has 8 cores (and 16 virtual processors) - so you see why choosing
concurrency factor of 14 is particularly bad in this setup.
Maurizio
On 14/09/15 12:03, Maurizio Cimadamore wrote:
Hi,
I realized that the concurrency factor inferred by the JDK build
might be too high; on a 16 core machine, concurrency is set to 14 -
which then leads to absurd load averages (50-ish) when
building/running tests. High load when building is not a big issue,
but when running test this almost always turns into spurious failures
due to timeouts. I know I can override the concurrency factor with
--with-jobs - but I was curious as to why the default parameter is
set to such aggressive value?
Thanks
Maurizio
