Multi-threaded code on ARM64 GHC runtime doesn't use all available cores
This is the machine: http://www.cnx-software.com/2016/04/30/setup-guide-mini-review-of-bq-aquaris-m10-ubuntu-edition-tablet-from-a-developers-perspective/
Haskell ray-tracer that uses Control.Parallel.Strategies and parBuffer that is working well on x64 machine and using all the cores available use only 2 cores from 4 in total on that ARM machine. This machine usually work on two cores only and when it sees that they are used more - it enables two more to get total of four cores. If I give "+RTS -N4" it works just fine. So I think the problem is that the runtime doesn't check for all available cores, but only for enabled.
In the first link you could see that "lscpu" returns 4 cores in total.
Trac metadata
Trac field | Value |
---|---|
Version | 7.10.3 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Runtime System |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | simonmar |
Operating system | |
Architecture |