Increase timer resolution for sampling profiler

Summary:
When using the sampling profiler on Windows, it is apparent that the
frequency is not as high as it is on other platforms. Doing some local
testing, the cause of the low frequency sampling is Windows timer
resolution when calling std::condition_variable::wait_for. By default,
this resolution is approximately 64Hz, meaning the sampling profiler
maxes out at ~64Hz. Setting `timeBeginPeriod(1)` improves sampling
frequency, maxing out at ~500Hz.

Reviewed By: neildhar

Differential Revision: D69500253

fbshipit-source-id: 3108c4629e6f2853731171e92ddf6af89792154b

lib/VM/Profiler/SamplingProfilerSampler.cpp

@@ -27,6 +27,13 @@
 #include <random>
 #include <thread>
 
+#if defined(_WINDOWS)
+#include <windows.h>
+// Must be included after windows.h
+#include <mmsystem.h>
+#include "llvh/ADT/ScopeExit.h"
+#endif
+
 namespace hermes {
 namespace vm {
 namespace sampling_profiler {
@@ -143,6 +150,14 @@ void Sampler::timerLoop(double meanHzFreq) {
   std::normal_distribution<> distribution{interval, interval / 2};
   std::unique_lock<std::mutex> uniqueLock(profilerLock_);
 
+#if defined(_WINDOWS)
+  // By default, timer resolution is approximately 64Hz on Windows, so if the
+  // meanHzFreq parameter is greater than 64, sampling will occur at a lower
+  // frequency than desired. Setting the period to 1 is the minimum useful
+  // value, resulting in timer resolution of roughly 1 millsecond.
+  timeBeginPeriod(1);
+  auto restorePeriod = llvh::make_scope_exit([] { timeEndPeriod(1); });
+#endif
   while (enabled_) {
     if (!sampleStacks()) {
       return;