/// <summary>
/// Determines the maximum number of actions to execute in parallel, taking into account the resources available on this machine.
/// </summary>
/// <returns>Max number of actions to execute in parallel</returns>
public virtual int GetMaxActionsToExecuteInParallel()
{
// Get the number of logical processors
int NumLogicalCores = Utils.GetLogicalProcessorCount();
// Use WMI to figure out physical cores, excluding hyper threading.
int NumPhysicalCores = Utils.GetPhysicalProcessorCount();
if (NumPhysicalCores == -1)
{
NumPhysicalCores = NumLogicalCores;
}
// The number of actions to execute in parallel is trying to keep the CPU busy enough in presence of I/O stalls.
int MaxActionsToExecuteInParallel = 0;
if (NumPhysicalCores < NumLogicalCores && ProcessorCountMultiplier != 1.0)
{
// The CPU has more logical cores than physical ones, aka uses hyper-threading.
// Use multiplier if provided
MaxActionsToExecuteInParallel = (int)(NumPhysicalCores * ProcessorCountMultiplier);
}
else if (NumPhysicalCores < NumLogicalCores && NumPhysicalCores > 4)
{
// The CPU has more logical cores than physical ones, aka uses hyper-threading.
// Use average of logical and physical if we have "lots of cores"
MaxActionsToExecuteInParallel = Math.Max((int)(NumPhysicalCores + NumLogicalCores) / 2, NumLogicalCores - 4);
}
// No hyper-threading. Only kicking off a task per CPU to keep machine responsive.
else
{
MaxActionsToExecuteInParallel = NumPhysicalCores;
}
#if !NET_CORE
if (Utils.IsRunningOnMono)
{
long PhysicalRAMAvailableMB = (new PerformanceCounter("Mono Memory", "Total Physical Memory").RawValue) / (1024 * 1024);
// heuristic: give each action at least 1.5GB of RAM (some clang instances will need more) if the total RAM is low, or 1GB on 16+GB machines
long MinMemoryPerActionMB = (PhysicalRAMAvailableMB < 16384) ? 3 * 1024 / 2 : 1024;
int MaxActionsAffordedByMemory = (int)(Math.Max(1, (PhysicalRAMAvailableMB) / MinMemoryPerActionMB));
MaxActionsToExecuteInParallel = Math.Min(MaxActionsToExecuteInParallel, MaxActionsAffordedByMemory);
}
#endif
MaxActionsToExecuteInParallel = Math.Max(1, Math.Min(MaxActionsToExecuteInParallel, MaxProcessorCount));
return(MaxActionsToExecuteInParallel);
}
