private void CollectInfrequently(long privateBytes)
{
// not thread-safe, only invoke from timer callback
Debug.Assert(_inPBytesMonitorThread == 1);
// The Server GC on x86 can traverse ~200mb per CPU per second, and the maximum heap size
// is about 3400mb, so the worst case scenario on x86 would take about 8 seconds to collect
// on a dual CPU box.
//
// The Server GC on x64 can traverse ~300mb per CPU per second, so a 6000 MB heap will take
// about 10 seconds to collect on a dual CPU box. The worst case scenario on x64 would make
// you want to return your hardware for a refund.
long timeSinceInducedGC = DateTime.UtcNow.Subtract(_inducedGCFinishTime).Ticks;
bool infrequent = (timeSinceInducedGC > _inducedGCMinInterval);
// if we haven't collected recently, or if the trim percent is low (less than 50%),
// we need to collect again
if (infrequent || _lastTrimPercent < 50)
{
// if we're inducing GC too frequently, increase the trim percentage, but don't go above 50%
if (!infrequent)
{
_lastTrimPercent = Math.Min(50, _lastTrimPercent + 10);
}
// if we're inducing GC infrequently, we may want to decrease the trim percentage
else if (_lastTrimPercent > 10 && timeSinceInducedGC > 2 * _inducedGCMinInterval)
{
_lastTrimPercent = Math.Max(10, _lastTrimPercent - 10);
}
int percent = (_totalCacheSize > 0) ? _lastTrimPercent : 0;
long trimmedOrExpired = 0;
if (percent > 0)
{
Stopwatch sw1 = Stopwatch.StartNew();
trimmedOrExpired = _appManager.TrimCaches(percent);
sw1.Stop();
_trimDurationTicks = sw1.Elapsed.Ticks;
}
//
if (trimmedOrExpired == 0 || _appManager.ShutdownInProgress)
{
return;
}
// collect and record statistics
Stopwatch sw2 = Stopwatch.StartNew();
GC.Collect();
sw2.Stop();
_inducedGCCount++; // only used for debugging
_inducedGCFinishTime = DateTime.UtcNow;
_inducedGCDurationTicks = sw2.Elapsed.Ticks;
_inducedGCPostPrivateBytes = NextSample();
_inducedGCPrivateBytesChange = privateBytes - _inducedGCPostPrivateBytes;
// target 3.3% Time in GC, but don't induce a GC more than once every 5 seconds
// Notes on calculation below: If G is duration of garbage collection and T is duration
// between starting the next collection, then G/T is % Time in GC. If we target 3.3%,
// then G/T = 3.3% = 33/1000, so T = G * 1000/33.
_inducedGCMinInterval = Math.Max(_inducedGCDurationTicks * 1000 / 33, 5 * TimeSpan.TicksPerSecond);
// no more frequently than every 60 seconds if change is less than 1%
if (_inducedGCPrivateBytesChange * 100 <= privateBytes)
{
_inducedGCMinInterval = Math.Max(_inducedGCMinInterval, 60 * TimeSpan.TicksPerSecond);
}
#if DBG
Debug.Trace("CacheMemory", "GC.COLLECT STATS "
+ "TrimCaches(" + percent + ")"
+ ", trimDurationSeconds=" + (_trimDurationTicks / TimeSpan.TicksPerSecond)
+ ", trimmedOrExpired=" + trimmedOrExpired
+ ", #secondsSinceInducedGC=" + (timeSinceInducedGC / TimeSpan.TicksPerSecond)
+ ", InducedGCCount=" + _inducedGCCount
+ ", gcDurationSeconds=" + (_inducedGCDurationTicks / TimeSpan.TicksPerSecond)
+ ", PrePrivateBytes=" + privateBytes
+ ", PostPrivateBytes=" + _inducedGCPostPrivateBytes
+ ", PrivateBytesChange=" + _inducedGCPrivateBytesChange
+ ", gcMinIntervalSeconds=" + (_inducedGCMinInterval / TimeSpan.TicksPerSecond));
#endif
#if PERF
SafeNativeMethods.OutputDebugString(" ** COLLECT **: "
+ percent + "%, "
+ (_trimDurationTicks / TimeSpan.TicksPerSecond) + " seconds"
+ ", infrequent=" + infrequent
+ ", removed=" + trimmedOrExpired
+ ", sinceIGC=" + (timeSinceInducedGC / TimeSpan.TicksPerSecond)
+ ", IGCCount=" + _inducedGCCount
+ ", IGCDuration=" + (_inducedGCDurationTicks / TimeSpan.TicksPerSecond)
+ ", preBytes=" + privateBytes
+ ", postBytes=" + _inducedGCPostPrivateBytes
+ ", byteChange=" + _inducedGCPrivateBytesChange
+ ", IGCMinInterval=" + (_inducedGCMinInterval / TimeSpan.TicksPerSecond) + "\n");
#endif
}
}