1 files changed, 95 insertions, 0 deletions
diff --git a/src/seastar/tests/unit/thread_context_switch_test.cc b/src/seastar/tests/unit/thread_context_switch_test.cc
new file mode 100644
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+++ b/src/seastar/tests/unit/thread_context_switch_test.cc
@@ -0,0 +1,95 @@
+/*
+ * This file is open source software, licensed to you under the terms
+ * of the Apache License, Version 2.0 (the "License").  See the NOTICE file
+ * distributed with this work for additional information regarding copyright
+ * ownership.  You may not use this file except in compliance with the License.
+ *
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+/*
+ * Copyright (C) 2015 Cloudius Systems, Ltd.
+ */
+
+#include <seastar/core/thread.hh>
+#include <seastar/core/semaphore.hh>
+#include <seastar/core/app-template.hh>
+#include <seastar/core/do_with.hh>
+#include <seastar/core/distributed.hh>
+#include <seastar/core/sleep.hh>
+
+using namespace seastar;
+using namespace std::chrono_literals;
+
+class context_switch_tester {
+    uint64_t _switches{0};
+    semaphore _s1{0};
+    semaphore _s2{0};
+    bool _done1{false};
+    bool _done2{false};
+    thread _t1{[this] { main1(); }};
+    thread _t2{[this] { main2(); }};
+private:
+    void main1() {
+        while (!_done1) {
+            _s1.wait().get();
+            ++_switches;
+            _s2.signal();
+        }
+        _done2 = true;
+    }
+    void main2() {
+        while (!_done2) {
+            _s2.wait().get();
+            ++_switches;
+            _s1.signal();
+        }
+    }
+public:
+    void begin_measurement() {
+        _s1.signal();
+    }
+    future<uint64_t> measure() {
+        _done1 = true;
+        return _t1.join().then([this] {
+            return _t2.join();
+        }).then([this] {
+            return _switches;
+        });
+    }
+    future<> stop() {
+        return make_ready_future<>();
+    }
+};
+
+int main(int ac, char** av) {
+    static const auto test_time = 5s;
+    return app_template().run_deprecated(ac, av, [] {
+        return do_with(distributed<context_switch_tester>(), [] (distributed<context_switch_tester>& dcst) {
+            return dcst.start().then([&dcst] {
+                return dcst.invoke_on_all(&context_switch_tester::begin_measurement);
+            }).then([] {
+                return sleep(test_time);
+            }).then([&dcst] {
+                return dcst.map_reduce0(std::mem_fn(&context_switch_tester::measure), uint64_t(), std::plus<uint64_t>());
+            }).then([] (uint64_t switches) {
+                switches /= smp::count;
+                fmt::print("context switch time: {:5.1f} ns\n",
+                      double(std::chrono::duration_cast<std::chrono::nanoseconds>(test_time).count()) / switches);
+            }).then([&dcst] {
+                return dcst.stop();
+            }).then([] {
+                engine_exit(0);
+            });
+        });
+    });
+}