[SDK] Optimize `CircularBufferBuckets.Copy` to use bulk array copies by matt-hensley · Pull Request #7670 · open-telemetry/opentelemetry-dotnet

matt-hensley · 2026-08-20T20:11:58Z

Changes

Optimizes CircularBufferBuckets.Copy to use bulk array copies instead of computing indices per-item.

Copy populates a snapshot from the circular bucket storage on every histogram collection. It previously iterated over all array items, computing a modulo for each to translate the logical index into the ring position.

The loop has been replaced with at most two Array.Copy calls. On the first copy, the items from the offset to the end of the array are copied. If there were too many elements to fit (offset + size > capacity), the values wrap, and a second copy moves the remaining items to the start of the destination array.

160 bucket benchmark run:

Scenario	Before	After	Improvement
CircularBufferBuckets.Copy, non-wrapped	257 ns	20.1 ns	~12.8×
ExponentialHistogramBuckets.SnapshotBuckets, non-wrapped	263 ns	18.5 ns	~14.2×
CircularBufferBuckets.Copy, wrapped	249 ns	21.8 ns	~11.4×
ExponentialHistogramBuckets.SnapshotBuckets, wrapped	241 ns	19.8 ns	~12.2×

Merge requirement checklist

CONTRIBUTING guidelines followed (license requirements, nullable enabled, static analysis, etc.)
Unit tests added/updated
Appropriate CHANGELOG.md files updated for non-trivial changes
Changes in public API reviewed (if applicable)

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Merged · refreshed 2026-08-21 08:03 UTC

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codecov · 2026-08-20T20:24:28Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.41%. Comparing base (551f6eb) to head (3a23974).
⚠️ Report is 2 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7670      +/-   ##
==========================================
- Coverage   91.42%   91.41%   -0.02%     
==========================================
  Files         318      318              
  Lines       17711    17715       +4     
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+ Hits        16193    16194       +1     
- Misses       1518     1521       +3

Flag	Coverage Δ
unittests-Project-Experimental	`91.48% <100.00%> (-0.05%)`	⬇️
unittests-Project-Stable	`91.46% <100.00%> (-0.07%)`	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
src/OpenTelemetry/Metrics/CircularBufferBuckets.cs	`100.00% <100.00%> (ø)`

... and 1 file with indirect coverage changes

….0 (#1316) Updated [OpenTelemetry.Exporter.OpenTelemetryProtocol](https://github.com/open-telemetry/opentelemetry-dotnet) from 1.17.0 to 1.18.0. <details> <summary>Release notes</summary> _Sourced from [OpenTelemetry.Exporter.OpenTelemetryProtocol's releases](https://github.com/open-telemetry/opentelemetry-dotnet/releases)._ ## 1.18.0 For highlights and announcements pertaining to this release see: [Release Notes > 1.18.0](https://github.com/open-telemetry/opentelemetry-dotnet/blob/main/RELEASENOTES.md#1180). The following changes are from the previous release [1.17.0](https://github.com/open-telemetry/opentelemetry-dotnet/releases/tag/core-1.17.0). * NuGet: [OpenTelemetry v1.18.0](https://www.nuget.org/packages/OpenTelemetry/1.18.0) * Fixed self-diagnostics log lines being silently dropped when an event message or parameter contained enough 3-byte UTF-8 characters to overflow the internal buffer estimate. Such content is now truncated. ([#7543](open-telemetry/opentelemetry-dotnet#7543)) * Fixed activity creation throwing when multiple tracer providers return a sampler attribute with the same key. ([#7558](open-telemetry/opentelemetry-dotnet#7558)) * Added the `otel.sdk.processor.log.processed` SDK self-observability metric. ([#7486](open-telemetry/opentelemetry-dotnet#7486)) * Added the `otel.sdk.processor.span.processed` SDK self-observability metric. ([#7598](open-telemetry/opentelemetry-dotnet#7598)) * `BatchActivityExportProcessor` and `SimpleActivityExportProcessor` no longer forward spans to the exporter once `Shutdown` has been called, and `BatchActivityExportProcessor.Shutdown` now waits for in-flight `OnEnd` calls to finish enqueueing before flushing. ([#7598](open-telemetry/opentelemetry-dotnet#7598)) * Fix logger, meter and tracer providers leaking background threads if an exception is thrown by their constructor after resource creation. ([#7615](open-telemetry/opentelemetry-dotnet#7615)) * `CircularBufferBuckets.Copy` optimized to use bulk array copies. ([#7670](open-telemetry/opentelemetry-dotnet#7670)) * Restored configured `MaxScale` after delta exponential histogram collection. ([#7671](open-telemetry/opentelemetry-dotnet#7671)) See [CHANGELOG](https://github.com/open-telemetry/opentelemetry-dotnet/blob/core-1.18.0/src/OpenTelemetry/CHANGELOG.md) for details. * NuGet: [OpenTelemetry.Api v1.18.0](https://www.nuget.org/packages/OpenTelemetry.Api/1.18.0) * Avoid formatting exceptions and creating exception attributes when `RecordException` is called on a span that is not recorded. ([#7669](open-telemetry/opentelemetry-dotnet#7669)) See [CHANGELOG](https://github.com/open-telemetry/opentelemetry-dotnet/blob/core-1.18.0/src/OpenTelemetry.Api/CHANGELOG.md) for details. * NuGet: [OpenTelemetry.Api.ProviderBuilderExtensions v1.18.0](https://www.nuget.org/packages/OpenTelemetry.Api.ProviderBuilderExtensions/1.18.0) No notable changes. See [CHANGELOG](https://github.com/open-telemetry/opentelemetry-dotnet/blob/core-1.18.0/src/OpenTelemetry.Api.ProviderBuilderExtensions/CHANGELOG.md) for details. * NuGet: [OpenTelemetry.Exporter.Console v1.18.0](https://www.nuget.org/packages/OpenTelemetry.Exporter.Console/1.18.0) * Added support for serializing attribute values that are key/value lists (`IEnumerable<KeyValuePair<string, object?>>`). These attributes will be serialized as JSON objects. ([#7015](open-telemetry/opentelemetry-dotnet#7015)) ... (truncated) ## 1.18.0-rc.1 The following changes are from the previous release [1.17.0](https://github.com/open-telemetry/opentelemetry-dotnet/releases/tag/core-1.17.0). * NuGet: [OpenTelemetry v1.18.0-rc.1](https://www.nuget.org/packages/OpenTelemetry/1.18.0-rc.1) * Fixed self-diagnostics log lines being silently dropped when an event message or parameter contained enough 3-byte UTF-8 characters to overflow the internal buffer estimate. Such content is now truncated. ([#7543](open-telemetry/opentelemetry-dotnet#7543)) * Fixed activity creation throwing when multiple tracer providers return a sampler attribute with the same key. ([#7558](open-telemetry/opentelemetry-dotnet#7558)) * Added the `otel.sdk.processor.log.processed` SDK self-observability metric. ([#7486](open-telemetry/opentelemetry-dotnet#7486)) * Added the `otel.sdk.processor.span.processed` SDK self-observability metric. ([#7598](open-telemetry/opentelemetry-dotnet#7598)) * `BatchActivityExportProcessor` and `SimpleActivityExportProcessor` no longer forward spans to the exporter once `Shutdown` has been called, and `BatchActivityExportProcessor.Shutdown` now waits for in-flight `OnEnd` calls to finish enqueueing before flushing. ([#7598](open-telemetry/opentelemetry-dotnet#7598)) * Fix logger, meter and tracer providers leaking background threads if an exception is thrown by their constructor after resource creation. ([#7615](open-telemetry/opentelemetry-dotnet#7615)) * `CircularBufferBuckets.Copy` optimized to use bulk array copies. ([#7670](open-telemetry/opentelemetry-dotnet#7670)) * Restored configured `MaxScale` after delta exponential histogram collection. ([#7671](open-telemetry/opentelemetry-dotnet#7671)) See [CHANGELOG](https://github.com/open-telemetry/opentelemetry-dotnet/blob/core-1.18.0-rc.1/src/OpenTelemetry/CHANGELOG.md) for details. * NuGet: [OpenTelemetry.Api v1.18.0-rc.1](https://www.nuget.org/packages/OpenTelemetry.Api/1.18.0-rc.1) * Avoid formatting exceptions and creating exception attributes when `RecordException` is called on a span that is not recorded. ([#7669](open-telemetry/opentelemetry-dotnet#7669)) See [CHANGELOG](https://github.com/open-telemetry/opentelemetry-dotnet/blob/core-1.18.0-rc.1/src/OpenTelemetry.Api/CHANGELOG.md) for details. * NuGet: [OpenTelemetry.Api.ProviderBuilderExtensions v1.18.0-rc.1](https://www.nuget.org/packages/OpenTelemetry.Api.ProviderBuilderExtensions/1.18.0-rc.1) No notable changes. See [CHANGELOG](https://github.com/open-telemetry/opentelemetry-dotnet/blob/core-1.18.0-rc.1/src/OpenTelemetry.Api.ProviderBuilderExtensions/CHANGELOG.md) for details. * NuGet: [OpenTelemetry.Exporter.Console v1.18.0-rc.1](https://www.nuget.org/packages/OpenTelemetry.Exporter.Console/1.18.0-rc.1) * Added support for serializing attribute values that are key/value lists (`IEnumerable<KeyValuePair<string, object?>>`). These attributes will be serialized as JSON objects. ([#7015](open-telemetry/opentelemetry-dotnet#7015)) See [CHANGELOG](https://github.com/open-telemetry/opentelemetry-dotnet/blob/core-1.18.0-rc.1/src/OpenTelemetry.Exporter.Console/CHANGELOG.md) for details. ... (truncated) ## 1.18.0-beta.1 The following changes are from the previous release [1.17.0-beta.1](https://github.com/open-telemetry/opentelemetry-dotnet/releases/tag/coreunstable-1.17.0-beta.1). * NuGet: [OpenTelemetry.Exporter.Prometheus.AspNetCore v1.18.0-beta.1](https://www.nuget.org/packages/OpenTelemetry.Exporter.Prometheus.AspNetCore/1.18.0-beta.1) * Fix concurrent scrapes returning an empty response under contention. Now the exporter will return an HTTP 500 error instead. ([#7571](open-telemetry/opentelemetry-dotnet#7571)) * Waiting for concurrent scrapes to finish before collecting no longer blocks, which could stall concurrent scrapes being waited on. ([#7571](open-telemetry/opentelemetry-dotnet#7571)) * Fixed the interaction between `PrometheusAspNetCoreOptions.TranslationStrategy` and content negotiation. The configured strategy is now applied before content negotiation, instead of the negotiated escaping scheme replacing the strategy's, and the `Content-Type` header now reports the escaping scheme that was applied rather than the one that was negotiated. ([#7610](open-telemetry/opentelemetry-dotnet#7610)) * Fixed metric values and histogram bucket bounds being written with 17 significant digits instead of their shortest round-trippable representation. ([#7589](open-telemetry/opentelemetry-dotnet#7589)) * Fixed the canonical representation used for histogram `le` and summary `quantile` label values falling back to 17 significant digits incorrectly. ([#7589](open-telemetry/opentelemetry-dotnet#7589)) * Fixed a race where a slow scrape could return an HTTP 200 instead of 408. ([#7615](open-telemetry/opentelemetry-dotnet#7615)) * Updated OpenTelemetry core component version(s) to `1.18.0`. ([#7674](open-telemetry/opentelemetry-dotnet#7674)) See [CHANGELOG](https://github.com/open-telemetry/opentelemetry-dotnet/blob/coreunstable-1.18.0-beta.1/src/OpenTelemetry.Exporter.Prometheus.AspNetCore/CHANGELOG.md) for details. * NuGet: [OpenTelemetry.Exporter.Prometheus.HttpListener v1.18.0-beta.1](https://www.nuget.org/packages/OpenTelemetry.Exporter.Prometheus.HttpListener/1.18.0-beta.1) * Fix concurrent scrapes returning an empty response under contention. Now the exporter will return an HTTP 500 error instead. ([#7571](open-telemetry/opentelemetry-dotnet#7571)) * Waiting for concurrent scrapes to finish before collecting no longer blocks, which could stall concurrent scrapes being waited on. ([#7571](open-telemetry/opentelemetry-dotnet#7571)) * A scrape which is still collecting when the listener is disposed now returns an HTTP 503 response. ([#7587](open-telemetry/opentelemetry-dotnet#7587)) * Shutting down the listener no longer waits indefinitely for its request processing loop to stop, and no longer throws if the loop faulted. ([#7587](open-telemetry/opentelemetry-dotnet#7587)) * Fixed the interaction between `PrometheusHttpListenerOptions.TranslationStrategy` and content negotiation. The configured strategy is now applied before content negotiation, instead of the negotiated escaping scheme replacing the strategy's, and the `Content-Type` header now reports the escaping scheme that was applied rather than the one that was negotiated. ([#7610](open-telemetry/opentelemetry-dotnet#7610)) * Fixed metric values and histogram bucket bounds being written with 17 significant digits instead of their shortest round-trippable representation. ([#7589](open-telemetry/opentelemetry-dotnet#7589)) * Fixed the canonical representation used for histogram `le` and summary `quantile` label values falling back to 17 significant digits incorrectly. ([#7589](open-telemetry/opentelemetry-dotnet#7589)) ... (truncated) Commits viewable in [compare view](open-telemetry/opentelemetry-dotnet@core-1.17.0...core-1.18.0). </details> [![Dependabot compatibility score](https://dependabot-badges.githubapp.com/badges/compatibility_score?dependency-name=OpenTelemetry.Exporter.OpenTelemetryProtocol&package-manager=nuget&previous-version=1.17.0&new-version=1.18.0)](https://docs.github.com/en/github/managing-security-vulnerabilities/about-dependabot-security-updates#about-compatibility-scores) Dependabot will resolve any conflicts with this PR as long as you don't alter it yourself. You can also trigger a rebase manually by commenting `@dependabot rebase`. [//]: # (dependabot-automerge-start) [//]: # (dependabot-automerge-end) --- <details> <summary>Dependabot commands and options</summary> <br /> You can trigger Dependabot actions by commenting on this PR: - `@dependabot rebase` will rebase this PR - `@dependabot recreate` will recreate this PR, overwriting any edits that have been made to it - `@dependabot show <dependency name> ignore conditions` will show all of the ignore conditions of the specified dependency - `@dependabot ignore this major version` will close this PR and stop Dependabot creating any more for this major version (unless you reopen the PR or upgrade to it yourself) - `@dependabot ignore this minor version` will close this PR and stop Dependabot creating any more for this minor version (unless you reopen the PR or upgrade to it yourself) - `@dependabot ignore this dependency` will close this PR and stop Dependabot creating any more for this dependency (unless you reopen the PR or upgrade to it yourself) </details> Signed-off-by: dependabot[bot] <support@github.com> Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

replace copy logic

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github-actions Bot added the pkg:OpenTelemetry Issues related to OpenTelemetry NuGet package label Aug 20, 2026

CHANGELOG

3a23974

matt-hensley marked this pull request as ready for review August 20, 2026 20:13

matt-hensley requested a review from a team as a code owner August 20, 2026 20:13

opentelemetry-pr-dashboard Bot mentioned this pull request Aug 20, 2026

Pull Request Dashboard #7539

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martincostello approved these changes Aug 21, 2026

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martincostello added this to the v1.18.0 milestone Aug 21, 2026

martincostello added this pull request to the merge queue Aug 21, 2026

Merged via the queue into open-telemetry:main with commit f6f6022 Aug 21, 2026
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[SDK] Optimize `CircularBufferBuckets.Copy` to use bulk array copies - #7670

[SDK] Optimize `CircularBufferBuckets.Copy` to use bulk array copies#7670
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