/// <summary>
/// New AddMemoryPressure implementation (used by RCW and the CLRServicesImpl class)
/// 1. Less sensitive than the original implementation (start budget 3 MB)
/// 2. Focuses more on newly added memory pressure
/// 3. Budget adjusted by effectiveness of last 3 triggered GC (add / remove ratio, max 10x)
/// 4. Budget maxed with 30% of current managed GC size
/// 5. If Gen2 GC is happening naturally, ignore past pressure
///
/// Here's a brief description of the ideal algorithm for Add/Remove memory pressure:
/// Do a GC when (HeapStart is less than X * MemPressureGrowth) where
/// - HeapStart is GC Heap size after doing the last GC
/// - MemPressureGrowth is the net of Add and Remove since the last GC
/// - X is proportional to our guess of the ummanaged memory death rate per GC interval,
/// and would be calculated based on historic data using standard exponential approximation:
/// Xnew = UMDeath/UMTotal * 0.5 + Xprev
/// </summary>
/// <param name="bytesAllocated"></param>
public static void AddMemoryPressure(long bytesAllocated)
{
if (bytesAllocated <= 0)
{
throw new ArgumentOutOfRangeException("bytesAllocated",
SR.ArgumentOutOfRange_NeedPosNum);
}
#if !BIT64
if (bytesAllocated > Int32.MaxValue)
{
throw new ArgumentOutOfRangeException("bytesAllocated",
SR.ArgumentOutOfRange_MustBeNonNegInt32);
}
#endif
CheckCollectionCount();
uint p = s_iteration % PressureCount;
long newMemValue = InterlockedAddMemoryPressure(ref s_addPressure[p], bytesAllocated);
Debug.Assert(PressureCount == 4, "GC.AddMemoryPressure contains unrolled loops which depend on the PressureCount");
if (newMemValue >= MinGCMemoryPressureBudget)
{
long add = s_addPressure[0] + s_addPressure[1] + s_addPressure[2] + s_addPressure[3] - s_addPressure[p];
long rem = s_removePressure[0] + s_removePressure[1] + s_removePressure[2] + s_removePressure[3] - s_removePressure[p];
long budget = MinGCMemoryPressureBudget;
if (s_iteration >= PressureCount) // wait until we have enough data points
{
// Adjust according to effectiveness of GC
// Scale budget according to past m_addPressure / m_remPressure ratio
if (add >= rem * MaxGCMemoryPressureRatio)
{
budget = MinGCMemoryPressureBudget * MaxGCMemoryPressureRatio;
}
else if (add > rem)
{
Debug.Assert(rem != 0);
// Avoid overflow by calculating addPressure / remPressure as fixed point (1 = 1024)
budget = (add * 1024 / rem) * budget / 1024;
}
}
// If still over budget, check current managed heap size
if (newMemValue >= budget)
{
long heapOver3 = RuntimeImports.RhGetCurrentObjSize() / 3;
if (budget < heapOver3) //Max
{
budget = heapOver3;
}
if (newMemValue >= budget)
{
// last check - if we would exceed 20% of GC "duty cycle", do not trigger GC at this time
if ((RuntimeImports.RhGetGCNow() - RuntimeImports.RhGetLastGCStartTime(2)) > (RuntimeImports.RhGetLastGCDuration(2) * 5))
{
RuntimeImports.RhCollect(2, InternalGCCollectionMode.NonBlocking);
CheckCollectionCount();
}
}
}
}
}