1/* 2 * Copyright (C) 2016 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17#include <algorithm> 18#include <chrono> 19#include <thread> 20#include <vector> 21 22#include <sys/capability.h> 23 24#include <cutils/sched_policy.h> 25 26#include <gtest/gtest.h> 27 28bool hasCapSysNice() { 29 __user_cap_header_struct header; 30 memset(&header, 0, sizeof(header)); 31 header.version = _LINUX_CAPABILITY_VERSION_3; 32 33 __user_cap_data_struct caps[_LINUX_CAPABILITY_U32S_3]; 34 if (capget(&header, &caps[0])) { 35 GTEST_LOG_(WARNING) << "failed to get process capabilities"; 36 return false; 37 } 38 39 auto nice_idx = CAP_TO_INDEX(CAP_SYS_NICE); 40 auto nice_mask = CAP_TO_MASK(CAP_SYS_NICE); 41 return caps[nice_idx].effective & nice_mask; 42} 43 44long long medianSleepTime() { 45 std::vector<long long> sleepTimes; 46 constexpr size_t numSamples = 100; 47 48 for (size_t i = 0; i < numSamples; i++) { 49 auto start = std::chrono::steady_clock::now(); 50 std::this_thread::sleep_for(std::chrono::nanoseconds(1)); 51 auto end = std::chrono::steady_clock::now(); 52 53 auto diff = end - start; 54 sleepTimes.push_back(diff.count()); 55 } 56 57 constexpr auto median = numSamples / 2; 58 std::nth_element(sleepTimes.begin(), sleepTimes.begin() + median, 59 sleepTimes.end()); 60 return sleepTimes[median]; 61} 62 63TEST(SchedPolicy, set_sched_policy) { 64 if (!hasCapSysNice()) { 65 GTEST_LOG_(INFO) << "skipping test that requires CAP_SYS_NICE"; 66 return; 67 } 68 69 // A measureable effect of scheduling policy is that the kernel has 800x 70 // greater slack time in waking up a sleeping background thread. 71 // 72 // Look for 100x difference in how long FB and BG threads actually sleep 73 // when trying to sleep for 1 ns. This difference is large enough not 74 // to happen by chance, but small enough (compared to 800x) to keep inherent 75 // fuzziness in scheduler behavior from causing false negatives. 76 const unsigned int BG_FG_SLACK_FACTOR = 100; 77 78 ASSERT_EQ(0, set_sched_policy(0, SP_BACKGROUND)); 79 auto bgSleepTime = medianSleepTime(); 80 81 ASSERT_EQ(0, set_sched_policy(0, SP_FOREGROUND)); 82 auto fgSleepTime = medianSleepTime(); 83 ASSERT_GT(bgSleepTime, fgSleepTime * BG_FG_SLACK_FACTOR); 84} 85 86TEST(SchedPolicy, get_sched_policy) { 87 SchedPolicy policy; 88 ASSERT_EQ(0, get_sched_policy(0, &policy)); 89 90 const char *policyName = get_sched_policy_name(policy); 91 EXPECT_NE(nullptr, policyName); 92 EXPECT_STRNE("error", policyName); 93 94 ASSERT_EQ(0, set_sched_policy(0, SP_BACKGROUND)); 95 SchedPolicy newPolicy; 96 ASSERT_EQ(0, get_sched_policy(0, &newPolicy)); 97 EXPECT_EQ(SP_BACKGROUND, newPolicy); 98} 99