Benchmark sine wave write rate limit (#3914)

Summary:
As mentioned at the [dev forum.](https://www.facebook.com/groups/rocksdb.dev/1693425187422655/)

Let me know if you would like me to do any changes!
Closes https://github.com/facebook/rocksdb/pull/3914

Differential Revision: D8452824

Pulled By: siying

fbshipit-source-id: 56439b3228ecdcc5a199d5198eff2fab553be961

tools/db_bench_tool.cc

@@ -889,6 +889,25 @@ DEFINE_bool(rate_limiter_auto_tuned, false,
             "Enable dynamic adjustment of rate limit according to demand for "
             "background I/O");
 
+
+DEFINE_bool(sine_write_rate, false,
+            "Use a sine wave write_rate_limit");
+
+DEFINE_uint64(sine_write_rate_interval_milliseconds, 10000,
+              "Interval of which the sine wave write_rate_limit is recalculated");
+
+DEFINE_double(sine_a, 1,
+             "A in f(x) = A sin(bx + c) + d");
+
+DEFINE_double(sine_b, 1,
+             "B in f(x) = A sin(bx + c) + d");
+
+DEFINE_double(sine_c, 0,
+             "C in f(x) = A sin(bx + c) + d");
+
+DEFINE_double(sine_d, 1,
+             "D in f(x) = A sin(bx + c) + d");
+
 DEFINE_bool(rate_limit_bg_reads, false,
             "Use options.rate_limiter on compaction reads");
 
@@ -1480,6 +1499,7 @@ class Stats {
  private:
   int id_;
   uint64_t start_;
+  uint64_t sine_interval_;
   uint64_t finish_;
   double seconds_;
   uint64_t done_;
@@ -1512,6 +1532,7 @@ class Stats {
     bytes_ = 0;
     seconds_ = 0;
     start_ = FLAGS_env->NowMicros();
+    sine_interval_ = FLAGS_env->NowMicros();
     finish_ = start_;
     last_report_finish_ = start_;
     message_.clear();
@@ -1584,6 +1605,18 @@ class Stats {
     }
   }
 
+  void ResetSineInterval() {
+    sine_interval_ = FLAGS_env->NowMicros();
+  }
+
+  uint64_t GetSineInterval() {
+    return sine_interval_;
+  }
+
+  uint64_t GetStart() {
+    return start_;
+  }
+
   void ResetLastOpTime() {
     // Set to now to avoid latency from calls to SleepForMicroseconds
     last_op_finish_ = FLAGS_env->NowMicros();
@@ -3350,6 +3383,9 @@ void VerifyDBFromDB(std::string& truth_db_name) {
       FLAGS_env->LowerThreadPoolCPUPriority(Env::HIGH);
     }
     options.env = FLAGS_env;
+    if (FLAGS_sine_write_rate) {
+      FLAGS_benchmark_write_rate_limit = static_cast<uint64_t>(SineRate(0));
+    }
 
     if (FLAGS_rate_limiter_bytes_per_sec > 0) {
       if (FLAGS_rate_limit_bg_reads &&
@@ -3583,6 +3619,10 @@ void VerifyDBFromDB(std::string& truth_db_name) {
     }
   }
 
+  double SineRate(double x) {
+    return FLAGS_sine_a*sin((FLAGS_sine_b*x) + FLAGS_sine_c) + FLAGS_sine_d;
+  }
+
   void DoWrite(ThreadState* thread, WriteMode write_mode) {
     const int test_duration = write_mode == RANDOM ? FLAGS_duration : 0;
     const int64_t num_ops = writes_ == 0 ? num_ : writes_;
@@ -3728,6 +3768,27 @@ void VerifyDBFromDB(std::string& truth_db_name) {
       }
       thread->stats.FinishedOps(db_with_cfh, db_with_cfh->db,
                                 entries_per_batch_, kWrite);
+      if (FLAGS_sine_write_rate) {
+        uint64_t now = FLAGS_env->NowMicros();
+
+        uint64_t usecs_since_last;
+        if (now > thread->stats.GetSineInterval()) {
+          usecs_since_last = now - thread->stats.GetSineInterval();
+        } else {
+          usecs_since_last = 0;
+        }
+
+        if (usecs_since_last >
+            (FLAGS_sine_write_rate_interval_milliseconds * uint64_t{1000})) {
+          double usecs_since_start =
+                  static_cast<double>(now - thread->stats.GetStart());
+          thread->stats.ResetSineInterval();
+          uint64_t write_rate =
+                  static_cast<uint64_t>(SineRate(usecs_since_start / 1000000.0));
+          thread->shared->write_rate_limiter.reset(
+                  NewGenericRateLimiter(write_rate));
+        }
+      }
       if (!s.ok()) {
         fprintf(stderr, "put error: %s\n", s.ToString().c_str());
         exit(1);