/// <summary>
/// Call this method to suppress expensive blocking Gen 2 garbage GCs in
/// scenarios where high-latency is unacceptable (e.g. processing typing input).
///
/// Blocking GCs will be re-enabled automatically after a short duration unless
/// UseLowLatencyModeForProcessingUserInput is called again.
/// </summary>
internal static void UseLowLatencyModeForProcessingUserInput()
{
if (s_delayMilliseconds <= 0)
{
// The registry key to opt out of Roslyn's SustainedLowLatency is set, or
// we haven't yet initialized the value.
return;
}
var currentMode = GCSettings.LatencyMode;
var currentDelay = s_delay;
if (currentMode != GCLatencyMode.SustainedLowLatency)
{
GCSettings.LatencyMode = GCLatencyMode.SustainedLowLatency;
// Restore the LatencyMode a short duration after the
// last request to UseLowLatencyModeForProcessingUserInput.
currentDelay = new ResettableDelay(s_delayMilliseconds);
currentDelay.Task.SafeContinueWith(_ => RestoreGCLatencyMode(currentMode), TaskScheduler.Default);
s_delay = currentDelay;
}
if (currentDelay != null)
{
currentDelay.Reset();
}
}
private static void RestoreGCLatencyMode(GCLatencyMode originalMode)
{
GCSettings.LatencyMode = originalMode;
s_delay = null;
// hint to the GC that if it postponed a gen 2 collection, now might be a good time to do it.
GC.Collect(2, GCCollectionMode.Optimized);
}
private void EnqueueUpdate()
{
const int WorkspaceUpdateDelay = 1500;
var delay = _delay;
if (delay == null)
{
var newDelay = new ResettableDelay(WorkspaceUpdateDelay);
if (Interlocked.CompareExchange(ref _delay, newDelay, null) == null)
{
var asyncToken = _asyncListener.BeginAsyncOperation("WorkspaceGraphQueryManager.EnqueueUpdate");
newDelay.Task.SafeContinueWithFromAsync(_ => UpdateAsync(), CancellationToken.None, TaskScheduler.Default)
.CompletesAsyncOperation(asyncToken);
}
return;
}
delay.Reset();
}
private void PostUpdate(Solution solution)
{
_delay = null;
lock (_gate)
{
// See if each context is still alive. It's possible it's already been GC'ed meaning we should stop caring about the query
_trackedQueries.RemoveAll(t => !IsTrackingContext(t.Item1));
if (_trackedQueries.IsEmpty())
{
_workspace.WorkspaceChanged -= OnWorkspaceChanged;
return;
}
}
EnqueueUpdateIfSolutionIsStale(solution);
}
