[PATCH] D94734: [lit] Use os.cpu_count() to cleanup TODO

[Julian Lettner via Phabricator via llvm-commits]

yln created this revision.
yln added reviewers: thakis, rnk, jdenny, serge-sans-paille.
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We can now use Python3.  Let's use `os.cpu_count()` to cleanup this
helper.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D94734

Files:
  llvm/utils/lit/lit/cl_arguments.py
  llvm/utils/lit/lit/run.py
  llvm/utils/lit/lit/util.py


Index: llvm/utils/lit/lit/util.py
===================================================================
--- llvm/utils/lit/lit/util.py
+++ llvm/utils/lit/lit/util.py
@@ -109,32 +109,19 @@
     return s
 
 
-# TODO(yln): multiprocessing.cpu_count()
-# TODO(python3): len(os.sched_getaffinity(0)) and os.cpu_count()
-def detectCPUs():
-    """Detects the number of CPUs on a system.
-
-    Cribbed from pp.
+def cpu_count():
+    """Return the number of CPUs in the system (like `os.cpu_count()`), but
+    default to 1 if undetermined.
 
     """
-    # Linux, Unix and MacOS:
-    if hasattr(os, 'sysconf'):
-        if 'SC_NPROCESSORS_ONLN' in os.sysconf_names:
-            # Linux & Unix:
-            ncpus = os.sysconf('SC_NPROCESSORS_ONLN')
-            if isinstance(ncpus, int) and ncpus > 0:
-                return ncpus
-        else:  # OSX:
-            return int(subprocess.check_output(['sysctl', '-n', 'hw.ncpu'],
-                                               stderr=subprocess.STDOUT))
-    # Windows:
-    if 'NUMBER_OF_PROCESSORS' in os.environ:
-        ncpus = int(os.environ['NUMBER_OF_PROCESSORS'])
-        if ncpus > 0:
-            # With more than 32 processes, process creation often fails with
-            # "Too many open files".  FIXME: Check if there's a better fix.
-            return min(ncpus, 32)
-    return 1  # Default
+    n = os.cpu_count() or 1
+
+    # On Windows, with more than 32 processes, process creation often fails with
+    # "Too many open files".  FIXME: Check if there's a better fix.
+    if platform.system() == 'Windows':
+        return min(n, 32)
+
+    return n
 
 
 def mkdir(path):
Index: llvm/utils/lit/lit/run.py
===================================================================
--- llvm/utils/lit/lit/run.py
+++ llvm/utils/lit/lit/run.py
@@ -110,7 +110,7 @@
     # threads counts toward the current process limit. Try to raise the (soft)
     # process limit so that tests don't fail due to resource exhaustion.
     def _increase_process_limit(self):
-        ncpus = lit.util.detectCPUs()
+        ncpus = lit.util.cpu_count()
         desired_limit = self.workers * ncpus * 2 # the 2 is a safety factor
 
         # Importing the resource module will likely fail on Windows.
Index: llvm/utils/lit/lit/cl_arguments.py
===================================================================
--- llvm/utils/lit/lit/cl_arguments.py
+++ llvm/utils/lit/lit/cl_arguments.py
@@ -23,7 +23,7 @@
             metavar="N",
             help="Number of workers used for testing",
             type=_positive_int,
-            default=lit.util.detectCPUs())
+            default=lit.util.cpu_count())
     parser.add_argument("--config-prefix",
             dest="configPrefix",
             metavar="NAME",


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