diff tests/test-simple-update.t @ 38731:ef3838a47503

worker: ability to disable thread unsafe tasks

The worker on Windows is implemented using a thread pool. If worker
tasks are not thread safe, badness can occur. In addition, if tasks
are executing CPU bound code and holding onto the GIL, there will be
non-substantial overhead in Python context switching between active
threads. This can result in significant slowdowns of tasks.

This commit teaches the code for determining whether to use a worker
to take thread safety into account. Effectively, thread unsafe tasks
don't use the thread-based worker on Windows.

Differential Revision: https://phab.mercurial-scm.org/D3962

--- a/tests/test-simple-update.t	Tue Jul 17 16:57:27 2018 -0700
+++ b/tests/test-simple-update.t	Wed Jul 18 09:46:45 2018 -0700
@@ -65,7 +65,7 @@
 
   $ cat <<EOF > forceworker.py
   > from mercurial import extensions, worker
-  > def nocost(orig, ui, costperop, nops):
+  > def nocost(orig, ui, costperop, nops, threadsafe=True):
   >     return worker._numworkers(ui) > 1
   > def uisetup(ui):
   >     extensions.wrapfunction(worker, 'worthwhile', nocost)