libcutils: add sched_policy test
Bug: 30597190
Change-Id: I51950e82235fa19bc92b3f7e8d190766d71af7df
Signed-off-by: Greg Hackmann <ghackmann@google.com>
diff --git a/libcutils/tests/Android.bp b/libcutils/tests/Android.bp
index 530c747..ada7d5f 100644
--- a/libcutils/tests/Android.bp
+++ b/libcutils/tests/Android.bp
@@ -21,6 +21,7 @@
srcs: [
"MemsetTest.cpp",
"PropertiesTest.cpp",
+ "sched_policy_test.cpp",
"trace-dev_test.cpp",
],
},
diff --git a/libcutils/tests/sched_policy_test.cpp b/libcutils/tests/sched_policy_test.cpp
new file mode 100644
index 0000000..173174a
--- /dev/null
+++ b/libcutils/tests/sched_policy_test.cpp
@@ -0,0 +1,98 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * 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.
+ */
+
+#include <algorithm>
+#include <chrono>
+#include <thread>
+#include <vector>
+
+#include <sys/capability.h>
+
+#include <cutils/sched_policy.h>
+
+#include <gtest/gtest.h>
+
+bool hasCapSysNice() {
+ __user_cap_header_struct header;
+ memset(&header, 0, sizeof(header));
+ header.version = _LINUX_CAPABILITY_VERSION_3;
+
+ __user_cap_data_struct caps[_LINUX_CAPABILITY_U32S_3];
+ if (capget(&header, &caps[0])) {
+ GTEST_LOG_(WARNING) << "failed to get process capabilities";
+ return false;
+ }
+
+ auto nice_idx = CAP_TO_INDEX(CAP_SYS_NICE);
+ auto nice_mask = CAP_TO_MASK(CAP_SYS_NICE);
+ return caps[nice_idx].effective & nice_mask;
+}
+
+long long medianSleepTime() {
+ std::vector<long long> sleepTimes;
+ constexpr size_t numSamples = 100;
+
+ for (size_t i = 0; i < numSamples; i++) {
+ auto start = std::chrono::steady_clock::now();
+ std::this_thread::sleep_for(std::chrono::nanoseconds(1));
+ auto end = std::chrono::steady_clock::now();
+
+ auto diff = end - start;
+ sleepTimes.push_back(diff.count());
+ }
+
+ constexpr auto median = numSamples / 2;
+ std::nth_element(sleepTimes.begin(), sleepTimes.begin() + median,
+ sleepTimes.end());
+ return sleepTimes[median];
+}
+
+TEST(SchedPolicy, set_sched_policy) {
+ if (!hasCapSysNice()) {
+ GTEST_LOG_(INFO) << "skipping test that requires CAP_SYS_NICE";
+ return;
+ }
+
+ // A measureable effect of scheduling policy is that the kernel has 800x
+ // greater slack time in waking up a sleeping background thread.
+ //
+ // Look for 100x difference in how long FB and BG threads actually sleep
+ // when trying to sleep for 1 ns. This difference is large enough not
+ // to happen by chance, but small enough (compared to 800x) to keep inherent
+ // fuzziness in scheduler behavior from causing false negatives.
+ const unsigned int BG_FG_SLACK_FACTOR = 100;
+
+ ASSERT_EQ(0, set_sched_policy(0, SP_BACKGROUND));
+ auto bgSleepTime = medianSleepTime();
+
+ ASSERT_EQ(0, set_sched_policy(0, SP_FOREGROUND));
+ auto fgSleepTime = medianSleepTime();
+ ASSERT_GT(bgSleepTime, fgSleepTime * BG_FG_SLACK_FACTOR);
+}
+
+TEST(SchedPolicy, get_sched_policy) {
+ SchedPolicy policy;
+ ASSERT_EQ(0, get_sched_policy(0, &policy));
+
+ const char *policyName = get_sched_policy_name(policy);
+ EXPECT_NE(nullptr, policyName);
+ EXPECT_STRNE("error", policyName);
+
+ ASSERT_EQ(0, set_sched_policy(0, SP_BACKGROUND));
+ SchedPolicy newPolicy;
+ ASSERT_EQ(0, get_sched_policy(0, &newPolicy));
+ EXPECT_EQ(SP_BACKGROUND, newPolicy);
+}