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Fix CounterGroup timer to use Stopwatch instead of DateTime.UtcNow #127303

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Fix CounterGroup timer to use Stopwatch instead of DateTime.UtcNow #127303

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389490d
fix: use Stopwatch instead of DateTime.UtcNow for timing in CounterGroup
unsafePtr Apr 22, 2026
4b3071d
refactor: use TimeSpan for polling interval in CounterGroup
unsafePtr Apr 23, 2026
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55 changes: 32 additions & 23 deletions src/libraries/System.Private.CoreLib/src/System/Diagnostics/Tracing/CounterGroup.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@
// The .NET Foundation licenses this file to you under the MIT license.

using System.Collections.Generic;
using System.Diagnostics;
using System.Runtime.Versioning;
using System.Threading;

Expand Down Expand Up @@ -92,7 +93,7 @@ private void OnEventSourceCommand(object? sender, EventCommandEventArgs e)

Debug.Assert((s_counterGroupEnabledList == null && !_eventSource.IsEnabled())
|| (_eventSource.IsEnabled() && s_counterGroupEnabledList!.Contains(this))
|| (_pollingIntervalInMilliseconds == 0 && !s_counterGroupEnabledList!.Contains(this))
|| (_pollingInterval == TimeSpan.Zero && !s_counterGroupEnabledList!.Contains(this))
|| (!_eventSource.IsEnabled() && !s_counterGroupEnabledList!.Contains(this)));
}
}
Expand Down Expand Up @@ -142,22 +143,24 @@ internal static CounterGroup GetCounterGroup(EventSource eventSource)

#region Timer Processing

private DateTime _timeStampSinceCollectionStarted;
private int _pollingIntervalInMilliseconds;
private DateTime _nextPollingTimeStamp;
private long _timeStampSinceCollectionStarted;
private TimeSpan _pollingInterval;
private long _nextPollingTimeStamp;

private void EnableTimer(float pollingIntervalInSeconds)
{
Debug.Assert(pollingIntervalInSeconds > 0);
Debug.Assert(Monitor.IsEntered(s_counterGroupLock));
if (_pollingIntervalInMilliseconds == 0 || pollingIntervalInSeconds * 1000 < _pollingIntervalInMilliseconds)
TimeSpan interval = TimeSpan.FromSeconds(pollingIntervalInSeconds);
if (_pollingInterval == TimeSpan.Zero || interval < _pollingInterval)
{
_pollingIntervalInMilliseconds = (int)(pollingIntervalInSeconds * 1000);
_pollingInterval = interval;
// Schedule IncrementingPollingCounter reset and synchronously reset other counters
HandleCountersReset();

_timeStampSinceCollectionStarted = DateTime.UtcNow;
_nextPollingTimeStamp = DateTime.UtcNow + new TimeSpan(0, 0, (int)pollingIntervalInSeconds);
long now = Stopwatch.GetTimestamp();
_timeStampSinceCollectionStarted = now;
_nextPollingTimeStamp = now + _pollingInterval.Ticks * Stopwatch.Frequency / TimeSpan.TicksPerSecond;

// Create the polling thread and init all the shared state if needed
if (s_pollingThread == null)
Expand Down Expand Up @@ -186,7 +189,7 @@ private void EnableTimer(float pollingIntervalInSeconds)
private void DisableTimer()
{
Debug.Assert(Monitor.IsEntered(s_counterGroupLock));
_pollingIntervalInMilliseconds = 0;
_pollingInterval = TimeSpan.Zero;
s_counterGroupEnabledList?.Remove(this);

if (s_needsResetIncrementingPollingCounters.Count > 0)
Expand Down Expand Up @@ -225,15 +228,15 @@ private void OnTimer()
{
if (_eventSource.IsEnabled())
{
DateTime now;
long now;
TimeSpan elapsed;
int pollingIntervalInMilliseconds;
TimeSpan pollingInterval;
DiagnosticCounter[] counters;
lock (s_counterGroupLock)
{
now = DateTime.UtcNow;
elapsed = now - _timeStampSinceCollectionStarted;
pollingIntervalInMilliseconds = _pollingIntervalInMilliseconds;
now = Stopwatch.GetTimestamp();
elapsed = Stopwatch.GetElapsedTime(_timeStampSinceCollectionStarted, now);
pollingInterval = _pollingInterval;
counters = new DiagnosticCounter[_counters.Count];
_counters.CopyTo(counters);
}
Expand All @@ -253,16 +256,22 @@ private void OnTimer()
// written to the old session or the new session. The behavior change is not being treated as a
// significant problem to address for now, but we can come back and address it if it turns out to
// be an actual issue.
counter.WritePayload((float)elapsed.TotalSeconds, pollingIntervalInMilliseconds);
counter.WritePayload((float)elapsed.TotalSeconds, (int)pollingInterval.TotalMilliseconds);
}

lock (s_counterGroupLock)
{
_timeStampSinceCollectionStarted = now;
TimeSpan delta = now - _nextPollingTimeStamp;
delta = _pollingIntervalInMilliseconds > delta.TotalMilliseconds ? TimeSpan.FromMilliseconds(_pollingIntervalInMilliseconds) : delta;
if (_pollingIntervalInMilliseconds > 0)
_nextPollingTimeStamp += TimeSpan.FromMilliseconds(_pollingIntervalInMilliseconds * Math.Ceiling(delta.TotalMilliseconds / _pollingIntervalInMilliseconds));
TimeSpan delta = Stopwatch.GetElapsedTime(_nextPollingTimeStamp, now);
if (delta < _pollingInterval)
{
delta = _pollingInterval;
}

if (_pollingInterval > TimeSpan.Zero)
{
_nextPollingTimeStamp += (long)Math.Ceiling(delta / _pollingInterval) * _pollingInterval.Ticks * Stopwatch.Frequency / TimeSpan.TicksPerSecond;
}
}
}
}
Expand Down Expand Up @@ -292,14 +301,14 @@ private static void PollForValues()
sleepEvent = s_pollingThreadSleepEvent;
foreach (CounterGroup counterGroup in s_counterGroupEnabledList!)
{
DateTime now = DateTime.UtcNow;
if (counterGroup._nextPollingTimeStamp < now + new TimeSpan(0, 0, 0, 0, 1))
long now = Stopwatch.GetTimestamp();
TimeSpan timeUntilNextPoll = Stopwatch.GetElapsedTime(now, counterGroup._nextPollingTimeStamp);
if (timeUntilNextPoll < TimeSpan.FromMilliseconds(1))
{
onTimers.Add(counterGroup);
}

int millisecondsTillNextPoll = (int)((counterGroup._nextPollingTimeStamp - now).TotalMilliseconds);
millisecondsTillNextPoll = Math.Max(1, millisecondsTillNextPoll);
int millisecondsTillNextPoll = Math.Max(1, (int)timeUntilNextPoll.TotalMilliseconds);
sleepDurationInMilliseconds = Math.Min(sleepDurationInMilliseconds, millisecondsTillNextPoll);
}

Expand Down
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