commit 68ae6ad12e4f89526638f167c380d0b28b3bdeac
author Elliott Hughes <enh@google.com> Tue Jul 21 16:11:30 2020 -0700
committer Elliott Hughes <enh@google.com> Tue Jul 21 16:34:58 2020 -0700
tree e18075751c1f0d08d94d7c6be14e1a18b560b285
parent c79ea239415963d4a38752d0f3efe50531c8e04f

Changes for #inclusivefixit.

Test: treehugger
Change-Id: I7ff0496c5c2792a41781e74634247f55b0548213

benchmarks/semaphore_benchmark.cpp

diff --git a/benchmarks/semaphore_benchmark.cpp b/benchmarks/semaphore_benchmark.cpp
index cf51489..ffccc82 100644
--- a/benchmarks/semaphore_benchmark.cpp
+++ b/benchmarks/semaphore_benchmark.cpp
@@ -28,8 +28,8 @@
   sem_init(&semaphore, 1, 1);
 
   while (state.KeepRunning()) {
-    int dummy;
-    sem_getvalue(&semaphore, &dummy);
+    int unused;
+    sem_getvalue(&semaphore, &unused);
   }
 }
 BIONIC_BENCHMARK(BM_semaphore_sem_getvalue);
@@ -44,112 +44,3 @@
   }
 }
 BIONIC_BENCHMARK(BM_semaphore_sem_wait_sem_post);
-
-// This test reports the overhead of the underlying futex wake syscall on
-// the producer. It does not report the overhead from issuing the wake to the
-// point where the posted consumer thread wakes up. It suffers from
-// clock_gettime syscall overhead. Lock the CPU speed for consistent results
-// as we may not reach >50% cpu utilization.
-//
-// We will run a background thread that catches the sem_post wakeup and
-// loops immediately returning back to sleep in sem_wait for the next one. This
-// thread is run with policy SCHED_OTHER (normal policy), a middle policy.
-//
-// The primary thread will run at SCHED_IDLE (lowest priority policy) when
-// monitoring the background thread to detect when it hits sem_wait sleep. It
-// will do so with no clock running. Once we are ready, we will switch to
-// SCHED_FIFO (highest priority policy) to time the act of running sem_post
-// with the benchmark clock running. This ensures nothing else in the system
-// can preempt our timed activity, including the background thread. We are
-// also protected with the scheduling policy of letting a process hit a
-// resource limit rather than get hit with a context switch.
-//
-// The background thread will start executing either on another CPU, or
-// after we back down from SCHED_FIFO, but certainly not in the context of
-// the timing of the sem_post.
-
-static atomic_int BM_semaphore_sem_post_running;
-
-static void* BM_semaphore_sem_post_start_thread(void* arg) {
-  sem_t* semaphore = reinterpret_cast<sem_t*>(arg);
-  while ((BM_semaphore_sem_post_running > 0) && !sem_wait(semaphore)) {
-  }
-  BM_semaphore_sem_post_running = -1;
-  return nullptr;
-}
-
-class SemaphoreFixture : public benchmark::Fixture {
- public:
-  void SetUp(const benchmark::State&) override {
-    sem_init(&semaphore, 0, 0);
-
-    pthread_attr_t attr;
-    pthread_attr_init(&attr);
-
-    memset(&param, 0, sizeof(param));
-    pthread_attr_setschedparam(&attr, &param);
-    pthread_attr_setschedpolicy(&attr, SCHED_OTHER);
-    pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
-    pthread_t pthread;
-    pthread_create(&pthread, &attr, BM_semaphore_sem_post_start_thread, &semaphore);
-    pthread_attr_destroy(&attr);
-
-    sched_setscheduler(0, SCHED_IDLE, &param);
-
-    BM_semaphore_sem_post_running = 1;
-    setup = true;
-  }
-
-  ~SemaphoreFixture() override {
-    if (setup) {
-      // Only do this if the test was actually run.
-      sched_setscheduler(0, SCHED_OTHER, &param);
-
-      if (BM_semaphore_sem_post_running > 0) {
-        BM_semaphore_sem_post_running = 0;
-      }
-      do {
-        sem_post(&semaphore);
-        sched_yield();
-      } while (BM_semaphore_sem_post_running != -1);
-    }
-  }
-
-  sem_t semaphore;
-  sched_param param;
-  bool setup = false;
-};
-
-// This is commented out because dynamic benchmark registering doesn't currently support fixtures.
-// Uncomment it and recompile to run this benchmark on every run.
-/* BENCHMARK_F(SemaphoreFixture, semaphore_sem_post)(benchmark::State& state) {
-  while (state.KeepRunning()) {
-    state.PauseTiming();
-
-    int trys = 3, dummy = 0;
-    do {
-      if (BM_semaphore_sem_post_running < 0) {
-        sched_setscheduler(0, SCHED_OTHER, &param);
-        fprintf(stderr, "BM_semaphore_sem_post: start_thread died unexpectedly\n");
-        abort();
-      }
-      sched_yield();
-      sem_getvalue(&semaphore, &dummy);
-      if (dummy < 0) {  // POSIX.1-2001 possibility 1
-        break;
-      }
-      if (dummy == 0) { // POSIX.1-2001 possibility 2
-        --trys;
-      }
-    } while (trys);
-
-    param.sched_priority = 1;
-    sched_setscheduler(0, SCHED_FIFO, &param);
-
-    state.ResumeTiming();
-    sem_post(&semaphore);
-
-    param.sched_priority = 0;
-    sched_setscheduler(0, SCHED_IDLE, &param);
-  }
-}*/