1 files changed, 1 insertions, 1 deletions

diff --git a/tox.ini b/tox.ini
index 626202301..9e2b5b2d3 100644
--- a/tox.ini
+++ b/tox.ini
@@ -29,7 +29,7 @@ deps =
   -r{toxinidir}/requirements.txt
   -r{toxinidir}/test-requirements.txt
 commands =
-  stestr run {posargs}
+  bash -c 'stestr run --concurrency=`python -c "import multiprocessing; print(int(multiprocessing.cpu_count()/2))"`'
   stestr slowest
 
 [testenv:bindep]