Limit parallelism in master.cfg

Author: alexreinking

master/master.cfg

@@ -17,7 +17,7 @@ from buildbot.changes.filter import ChangeFilter
 from buildbot.config import BuilderConfig
 from buildbot.locks import WorkerLock
 from buildbot.process.factory import BuildFactory
-from buildbot.process.properties import Interpolate, Property, Transform
+from buildbot.process.properties import Interpolate, Property, Transform, renderer
 from buildbot.reporters.generators.build import BuildStartEndStatusGenerator
 from buildbot.reporters.github import GitHubStatusPush
 from buildbot.reporters.message import MessageFormatterRenderable
@@ -50,6 +50,20 @@ def Merge(prop, *args):
 # a shorter alias to save typing.
 c = BuildmasterConfig = {}
 
+
+@renderer
+def jobs_per_build(props):
+    worker_info = props.getBuild().getWorkerInfo()
+    numcpus = int(worker_info.get("numcpus", 1))
+    workername = props.getProperty("workername", "")
+    max_builds = 1
+    for w in c["workers"]:
+        if w.name == workername:
+            max_builds = w.max_builds or 1
+            break
+    return str(max(1, numcpus // max_builds))
+
+
 # SERVER SETTINGS
 
 REPO_DIR = Path(__file__).parent.parent.resolve()
@@ -512,7 +526,7 @@ def get_cmake_definitions(builder_type, halide_target="host", wasm_jit="wabt", e
 
 
 def get_build_command(build_dir, targets=None):
-    cmd = ["cmake", "--build", build_dir]
+    cmd = ["cmake", "--build", build_dir, "-j", jobs_per_build]
 
     if targets:
         cmd.append("--target")
@@ -1098,7 +1112,7 @@ def add_test_steps(factory, builder_type):
                     timeout=3600,
                     labels=parallel_test_labels,
                     exclude_tests=exclude_tests,
-                    jobs=Interpolate("%(worker:numcpus)s"),
+                    jobs=jobs_per_build,
                     **get_ctest_options(builder_type),
                 )
             )