diff --git a/mercurial/worker.py b/mercurial/worker.py --- a/mercurial/worker.py +++ b/mercurial/worker.py @@ -57,18 +57,27 @@ 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 = True 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. @@ -82,9 +91,13 @@ 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,)) 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 < 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)