Patchwork D3962: worker: ability to disable thread unsafe tasks

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Submitter phabricator
Date July 19, 2018, 12:18 p.m.
Message ID <0aef776fcb85597471151c5cfaa1e4b1@localhost.localdomain>
Download mbox | patch
Permalink /patch/32912/
State Not Applicable
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phabricator - July 19, 2018, 12:18 p.m.
This revision was automatically updated to reflect the committed changes.
Closed by commit rHGef3838a47503: worker: ability to disable thread unsafe tasks (authored by indygreg, committed by ).

CHANGED PRIOR TO COMMIT
  https://phab.mercurial-scm.org/D3962?vs=9623&id=9630#toc

REPOSITORY
  rHG Mercurial

CHANGES SINCE LAST UPDATE
  https://phab.mercurial-scm.org/D3962?vs=9623&id=9630

REVISION DETAIL
  https://phab.mercurial-scm.org/D3962

AFFECTED FILES
  mercurial/worker.py
  tests/test-simple-update.t

CHANGE DETAILS




To: indygreg, #hg-reviewers, lothiraldan
Cc: yuja, mercurial-devel

Patch

diff --git a/tests/test-simple-update.t b/tests/test-simple-update.t
--- a/tests/test-simple-update.t
+++ b/tests/test-simple-update.t
@@ -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)
diff --git a/mercurial/worker.py b/mercurial/worker.py
--- a/mercurial/worker.py
+++ b/mercurial/worker.py
@@ -63,18 +63,27 @@ 
 
 if pycompat.isposix or pycompat.iswindows:
     _STARTUP_COST = 0.01
+    # The Windows worker is thread based. If tasks are CPU bound, threads
+    # in the presence of the GIL result in excessive context switching and
+    # this overhead can slow down execution.
+    _DISALLOW_THREAD_UNSAFE = pycompat.iswindows
 else:
     _STARTUP_COST = 1e30
+    _DISALLOW_THREAD_UNSAFE = False
 
-def worthwhile(ui, costperop, nops):
+def worthwhile(ui, costperop, nops, threadsafe=True):
     '''try to determine whether the benefit of multiple processes can
     outweigh the cost of starting them'''
+
+    if not threadsafe and _DISALLOW_THREAD_UNSAFE:
+        return False
+
     linear = costperop * nops
     workers = _numworkers(ui)
     benefit = linear - (_STARTUP_COST * workers + linear / workers)
     return benefit >= 0.15
 
-def worker(ui, costperarg, func, staticargs, args):
+def worker(ui, costperarg, func, staticargs, args, threadsafe=True):
     '''run a function, possibly in parallel in multiple worker
     processes.
 
@@ -88,9 +97,13 @@ 
 
     args - arguments to split into chunks, to pass to individual
     workers
+
+    threadsafe - whether work items are thread safe and can be executed using
+    a thread-based worker. Should be disabled for CPU heavy tasks that don't
+    release the GIL.
     '''
     enabled = ui.configbool('worker', 'enabled')
-    if enabled and worthwhile(ui, costperarg, len(args)):
+    if enabled and worthwhile(ui, costperarg, len(args), threadsafe=threadsafe):
         return _platformworker(ui, func, staticargs, args)
     return func(*staticargs + (args,))