/// <summary>
/// Register a notification to occur *AFTER* a GC occurs in which the memory load changes from within the bound specified
/// to outside of the bound specified. This notification will occur once. If repeated notifications are required, the notification
/// must be reregistered. The notification will occur on a thread which should not be blocked. Complex processing in the notification should defer work to the threadpool.
/// </summary>
/// <param name="lowMemoryPercent">percent of HighMemoryLoadThreshold to use as lower bound. Must be a number >= 0 or an ArgumentOutOfRangeException will be thrown.</param>
/// <param name="highMemoryPercent">percent of HighMemoryLoadThreshold use to use as lower bound. Must be a number > lowMemory or an ArgumentOutOfRangeException will be thrown. </param>
/// <param name="notification">delegate to invoke when operation occurs</param>s
internal static void RegisterMemoryLoadChangeNotification(float lowMemoryPercent, float highMemoryPercent, Action notification)
{
if (highMemoryPercent < 0 || highMemoryPercent > 1.0 || highMemoryPercent <= lowMemoryPercent)
{
throw new ArgumentOutOfRangeException(nameof(highMemoryPercent));
}
if (lowMemoryPercent < 0)
{
throw new ArgumentOutOfRangeException(nameof(lowMemoryPercent));
}
if (notification == null)
{
throw new ArgumentNullException(nameof(notification));
}
lock (s_notifications)
{
s_notifications.Add(new MemoryLoadChangeNotification(lowMemoryPercent, highMemoryPercent, notification));
if (s_notifications.Count == 1)
{
Gen2GcCallback.Register(InvokeMemoryLoadChangeNotifications);
}
}
}
private void Restock(out object returnBuffer)
{
lock (this)
{
// Try again after getting the lock as another thread could have just filled the free list. If we don't check
// then we unnecessarily grab a new set of buffers because we think we are out.
if (_freeList.TryPop(out returnBuffer))
{
return;
}
// Lazy init, Ask that TrimFreeListIfNeeded be called on every Gen 2 GC.
if (_restockSize == 0)
{
Gen2GcCallback.Register(Gen2GcCallbackFunc, this);
}
// Indicate to the trimming policy that the free list is insufficient.
_moreThanFreeListNeeded = true;
PinnableBufferCacheEventSource.Log.AllocateBufferFreeListEmpty(_cacheName, _notGen2.Count);
// Get more buffers if needed.
if (_notGen2.Count == 0)
{
CreateNewBuffers();
}
// We have no buffers in the aged freelist, so get one from the newer list. Try to pick the best one.
// Debug.Assert(_notGen2.Count != 0);
int idx = _notGen2.Count - 1;
if (GC.GetGeneration(_notGen2[idx]) < GC.MaxGeneration && GC.GetGeneration(_notGen2[0]) == GC.MaxGeneration)
{
idx = 0;
}
returnBuffer = _notGen2[idx];
_notGen2.RemoveAt(idx);
// Remember any sub-optimal buffer so we don't put it on the free list when it gets freed.
if (PinnableBufferCacheEventSource.Log.IsEnabled() && GC.GetGeneration(returnBuffer) < GC.MaxGeneration)
{
PinnableBufferCacheEventSource.Log.AllocateBufferFromNotGen2(_cacheName, _notGen2.Count);
}
// If we have a Gen1 collection, then everything on _notGen2 should have aged. Move them to the _freeList.
if (!AgePendingBuffers())
{
// Before we could age at set of buffers, we have handed out half of them.
// This implies we should be proactive about allocating more (since we will trim them if we over-allocate).
if (_notGen2.Count == _restockSize / 2)
{
PinnableBufferCacheEventSource.Log.DebugMessage("Proactively adding more buffers to aging pool");
CreateNewBuffers();
}
}
}
}