Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Lock-free updates for Histogram #2951

Merged
merged 7 commits into from
Mar 2, 2022
Merged

Lock-free updates for Histogram #2951

Show file tree
Hide file tree
Changes from 1 commit
Commits
Show all changes
7 commits
Select commit Hold shift + click to select a range
1dec481
Lock-free updates for Histogram
utpilla Feb 25, 2022
ad8c345
Add unchecked
utpilla Feb 26, 2022
5090322
Merge branch 'main' into utpilla/Lock-free-Histogram-Update
cijothomas Mar 1, 2022
c680c49
Address PR comments
utpilla Mar 2, 2022
e7270f3
Merge branch 'utpilla/Lock-free-Histogram-Update' of https://github.c…
utpilla Mar 2, 2022
8467fa1
Update src/OpenTelemetry/CHANGELOG.md
cijothomas Mar 2, 2022
5e9a98d
Update src/OpenTelemetry/CHANGELOG.md
utpilla Mar 2, 2022
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
2 changes: 2 additions & 0 deletions src/OpenTelemetry/Metrics/HistogramBuckets.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,8 @@ public class HistogramBuckets

internal double SnapshotSum;

internal int UsingHistogram = 0;
utpilla marked this conversation as resolved.
Show resolved Hide resolved

internal HistogramBuckets(double[] explicitBounds)
{
this.ExplicitBounds = explicitBounds;
Expand Down
17 changes: 13 additions & 4 deletions src/OpenTelemetry/Metrics/MetricPoint.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -323,11 +323,20 @@ internal void Update(double number)
}
}

lock (this.histogramBuckets.LockObject)
var sw = default(SpinWait);
while (true)
{
this.runningValue.AsLong++;
this.histogramBuckets.RunningSum += number;
this.histogramBuckets.RunningBucketCounts[i]++;
if (Interlocked.Exchange(ref this.histogramBuckets.UsingHistogram, 1) == 0)
{
this.runningValue.AsLong++;
Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I haven't look into the underlying code, wonder if this ++ might throw (e.g. integer overflow case). If that's the case, we might need to make sure we release the spinlock.

Copy link
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

We don't acquire any lock in the first place to be released. SpinWait is used to just smartly apply context switch for the thread.

Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

one Ln335 we set this.histogramBuckets.UsingHistogram = 0, if we throw before this, all other threads would spin I guess?

Copy link
Member

@reyang reyang Feb 25, 2022 •
edited
Loading

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I think unchecked would solve the problem here.

Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

https://github.com/open-telemetry/opentelemetry-dotnet/blob/main/src/OpenTelemetry/Internal/CircularBuffer.cs#L139-L143 We could explore if we need to have an exit plan like done for CircularBuffer.

this.histogramBuckets.RunningSum += number;
this.histogramBuckets.RunningBucketCounts[i]++;

this.histogramBuckets.UsingHistogram = 0;
break;
}

sw.SpinOnce();
cijothomas marked this conversation as resolved.
Show resolved Hide resolved
}

break;
Expand Down