perf(runtime): lazily allocate activation request tracking by ReubenBond · Pull Request #10115 · dotnet/orleans

ReubenBond · 2026-05-17T05:22:38Z

Summary

Lazily allocate activation waiting/running request collections instead of creating them for every activation.
Return empty request tracking collections for reuse.
Preserve null-safe inactivity and request-count semantics for activations with no queued or running requests.

Validation

dotnet build src\Orleans.Runtime\Orleans.Runtime.csproj --nologo --verbosity minimal -property:UseSharedCompilation=false
dotnet build test\Grains\TestVersionGrains\TestVersionGrains.csproj --nologo --verbosity minimal -property:UseSharedCompilation=false
dotnet build test\Grains\TestVersionGrains2\TestVersionGrains2.csproj --nologo --verbosity minimal -property:UseSharedCompilation=false
dotnet test test\Orleans.Runtime.Tests\Orleans.Runtime.Tests.csproj --no-build --nologo --verbosity minimal -property:UseSharedCompilation=false

Microsoft Reviewers: Open in CodeFlow

Copilot

Pull request overview

This PR reduces per-activation allocations in the Orleans runtime by lazily creating (and reusing) the collections used to track queued and running requests for an activation, while keeping existing “no requests” semantics intact.

Changes:

Lazily allocate _waitingRequests and _runningRequests in ActivationData and update related logic to be null-safe.
Introduce shared pools for the request-tracking collections and return them for reuse when they become empty.

Show a summary per file

File	Description
`src/Orleans.Runtime/Catalog/GrainTypeSharedContext.cs`	Adds shared pools plus rent/return helpers for request-tracking collections.
`src/Orleans.Runtime/Catalog/ActivationData.cs`	Switches request tracking to lazy allocation, adds return-to-pool logic, and updates null-safe request-count/inactivity checks.

Copilot's findings

Files reviewed: 2/2 changed files
Comments generated: 1

Copilot

Review details

Suppressed comments (1)

src/Orleans.Runtime/Catalog/GrainTypeSharedContext.cs:26

The new request-tracking pools are unbounded (ConcurrentStack with no size cap) and will retain the backing arrays of any large List/Dictionary instances which get returned. In a long-running silo, a transient spike in queued/running requests could permanently increase steady-state memory usage (large-capacity collections stay rooted by the pool even after load subsides). Consider bounding the pool size and/or avoiding pooling large-capacity collections (e.g., discard or trim when above a threshold) to prevent memory bloat.

    private static readonly ConcurrentStack<Dictionary<Message, CoarseStopwatch>> RunningRequestsMapPool = new();
    private static readonly ConcurrentStack<List<(Message Message, CoarseStopwatch QueuedTime)>> WaitingRequestsListPool = new();

Files reviewed: 2/2 changed files
Comments generated: 0 new
Review effort level: Lite

Copilot

Review details

Suppressed comments (1)

src/Orleans.Runtime/Catalog/ActivationData.cs:505

GetRequestCount already holds this, but calling WaitingCount re-enters the monitor on every overload check and activation-metrics read. Since the waiting count can be read safely under this existing lock, use _waitingRequests?.Count ?? 0 directly here to avoid adding a synchronization operation to this hot path.

            return (_runningRequests?.Count ?? 0) + WaitingCount;

Files reviewed: 1/1 changed files
Comments generated: 0 new
Review effort level: Lite

Copilot

Review details

Files reviewed: 4/4 changed files
Comments generated: 0 new
Review effort level: Lite

github-actions · 2026-08-23T16:34:11Z

Code coverage

52.17% line coverage - 52,895 / 101,389 lines

Coverage details

Source files: 1,383
Scope: BVT, SlowBVT, and Functional tests on Linux with .NET 10
Sources: maintained repository code under src/
Commit: 384991520c
View the test run and merged coverage artifact
View the coverage reporting run

Rent waiting and running request collections only while an activation uses them. Bound pooled capacity and synchronize state observations so collection reuse preserves activation ownership and lifecycle invariants. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Use one pooled tracker lease per activation, return it only after waiting and running requests are empty, and collapse stateless-worker status reads to one lock acquisition. Add deterministic transition, cancellation, deactivation, reuse, double-return, and concurrent-reader coverage. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Copilot review overview

Review tier: Lite
Findings: 1 · 1

New issues introduced by this change (2)

Severity	Finding
	`src/Orleans.Runtime/Catalog/StatelessWorkerGrainContext.cs` — GetRequestStatus() acquires the ActivationData lock for every worker inspected. In…
	`src/Orleans.Runtime/Catalog/ActivationData.cs` — These public request-status properties now unconditionally take the activation lock. They are…

+                    var candidate = _workers[i];
+                    var status = candidate.GetRequestStatus();
+                    if (status.IsInactive)
                    {


Copilot

Copilot review overview

Review tier: Lite
Findings: 2 · 1

New issues introduced by this change (2)

Severity	Finding
	`src/Orleans.Runtime/Catalog/ActivationData.cs` — Throwing InvalidOperationException when a running request cannot be removed introduces a new…
	`test/Orleans.Runtime.Internal.Tests/ActivationsLifeCycleTests/ActivationRequestTrackerTests.cs` — Using TaskCreationOptions.LongRunning here can create a dedicated thread per producer (64 threads),…

Pre-existing issues (1)

Severity	Finding
	`src/Orleans.Runtime/Catalog/StatelessWorkerGrainContext.cs` — GetRequestStatus() acquires the ActivationData lock for every worker inspected. In… View comment

Issues resolved since last review (1)

Severity	Finding
	`src/Orleans.Runtime/Catalog/ActivationData.cs` — These public request-status properties now unconditionally take the activation lock. They are… View resolved comment

+            if (!_requestTracker!.RemoveRunning(message))
+            {
+                throw new InvalidOperationException($"Completed request {message} was not tracked by activation {this}.");
+            }
+
+            ReturnRequestTrackerIfEmpty();


+                    tracker.AddWaiting(messages[index]);
+                    UpdateRequestStatus(activation, tracker);
+                }
+            }, cancellationToken, TaskCreationOptions.LongRunning, TaskScheduler.Default)).ToArray();


ReubenBond requested a lite review from Copilot May 17, 2026 15:17

Copilot started reviewing on behalf of ReubenBond May 17, 2026 15:18 View session

Copilot AI reviewed May 17, 2026

View reviewed changes

Comment thread src/Orleans.Runtime/Catalog/GrainTypeSharedContext.cs Outdated

ReubenBond changed the title ~~Lazily allocate activation request tracking~~ perf(runtime): lazily allocate activation request tracking May 29, 2026

Copilot AI review requested due to automatic review settings August 18, 2026 09:41

ReubenBond force-pushed the rebond/lazy-activation-request-tracking branch from 2119bab to 932b619 Compare August 18, 2026 09:41

Copilot started reviewing on behalf of ReubenBond August 18, 2026 09:41 View session

Copilot AI reviewed Aug 18, 2026

View reviewed changes

Copilot AI review requested due to automatic review settings August 21, 2026 21:14

ReubenBond force-pushed the rebond/lazy-activation-request-tracking branch from 932b619 to fe6d45c Compare August 21, 2026 21:14

Copilot started reviewing on behalf of ReubenBond August 21, 2026 21:14 View session

Copilot AI reviewed Aug 21, 2026

View reviewed changes

ReubenBond marked this pull request as ready for review August 21, 2026 22:30

Copilot AI review requested due to automatic review settings August 23, 2026 15:51

ReubenBond force-pushed the rebond/lazy-activation-request-tracking branch from fe6d45c to 3849915 Compare August 23, 2026 15:51

Copilot started reviewing on behalf of ReubenBond August 23, 2026 15:51 View session

Copilot AI reviewed Aug 23, 2026

View reviewed changes

Copilot AI review requested due to automatic review settings August 28, 2026 17:26

ReubenBond force-pushed the rebond/lazy-activation-request-tracking branch from 3849915 to aedf82f Compare August 28, 2026 17:26

Copilot started reviewing on behalf of ReubenBond August 28, 2026 17:26 View session

ReubenBond and others added 3 commits August 28, 2026 10:26

test(runtime): strengthen activation request tracker coverage

2efa3fe

Copilot AI reviewed Aug 28, 2026

View reviewed changes

Comment thread src/Orleans.Runtime/Catalog/StatelessWorkerGrainContext.cs

Comment on lines +268 to 271

var candidate = _workers[i];

var status = candidate.GetRequestStatus();

if (status.IsInactive)

{

Comment thread src/Orleans.Runtime/Catalog/ActivationData.cs Outdated

perf(runtime): use lock-free activation request status

9c6fbca

Copilot AI review requested due to automatic review settings August 28, 2026 18:18

ReubenBond force-pushed the rebond/lazy-activation-request-tracking branch from aedf82f to 9c6fbca Compare August 28, 2026 18:18

Copilot started reviewing on behalf of ReubenBond August 28, 2026 18:18 View session

Copilot AI reviewed Aug 28, 2026

View reviewed changes

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perf(runtime): lazily allocate activation request tracking - #10115

perf(runtime): lazily allocate activation request tracking#10115
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