Add a test

Author: joker-eph

llvm/utils/lit/lit/run.py

@@ -82,9 +82,14 @@ def _execute(self, deadline):
 
         # Windows has a limit of 60 workers per pool, so we need to use multiple pools
         # if we have more workers requested than the limit.
+        # Also, allow to override the limit with the LIT_WINDOWS_MAX_WORKERS_PER_POOL environment variable.
         max_workers_per_pool = (
             WINDOWS_MAX_WORKERS_PER_POOL if os.name == "nt" else self.workers
         )
+        max_workers_per_pool = int(
+            os.getenv("LIT_WINDOWS_MAX_WORKERS_PER_POOL", max_workers_per_pool)
+        )
+
         num_pools = max(1, _ceilDiv(self.workers, max_workers_per_pool))
 
         # Distribute self.workers across num_pools as evenly as possible

llvm/utils/lit/tests/windows-pools.py

@@ -0,0 +1,27 @@
+# Create a directory with 20 files and check the number of pools and workers per pool that lit will use.
+
+# RUN: rm -Rf %t.dir && mkdir -p %t.dir
+# RUN: python -c "for i in range(20): open(f'%t.dir/file{i}.txt', 'w').write('RUN:')"
+
+# RUN:  echo "import lit.formats" > %t.dir/lit.cfg
+# RUN:  echo "config.name = \"top-level-suite\"" >> %t.dir/lit.cfg
+# RUN:  echo "config.suffixes = [\".txt\"]" >> %t.dir/lit.cfg
+# RUN:  echo "config.test_format = lit.formats.ShTest()" >> %t.dir/lit.cfg
+
+
+# 15 workers per pool max, 100 workers total max: we expect lit to cap the workers to the number of files
+# RUN: env "LIT_WINDOWS_MAX_WORKERS_PER_POOL=15" %{lit} -s %t.dir/ -j100 > %t.out 2>&1
+# CHECK: Using 2 pools balancing 20 workers total distributed as [10, 10]
+# CHECK: Passed: 20
+
+# 5 workers per pool max, 17 workers total max
+# RUN: env "LIT_WINDOWS_MAX_WORKERS_PER_POOL=5" %{lit} -s %t.dir/ -j17 >> %t.out 2>&1
+# CHECK: Using 4 pools balancing 17 workers total distributed as [5, 4, 4, 4]
+# CHECK: Passed: 20
+
+# 19 workers per pool max, 19 workers total max
+# RUN: env "LIT_WINDOWS_MAX_WORKERS_PER_POOL=19" %{lit} -s %t.dir/ -j19 >> %t.out 2>&1
+# CHECK-NOT: workers total distributed as
+# CHECK: Passed: 20
+
+# RUN: cat %t.out | FileCheck %s