Improve UnwindInfoTable's performance by eduardo-vp · Pull Request #125545 · dotnet/runtime

eduardo-vp · 2026-03-14T01:05:52Z

Place the entries of UnwindInfoTable in a buffer and flush such that we amortize the cost of the operations (pRtlAddGrowableFunctionTable + pRtlDeleteGrowableFunctionTable) to create the internal table of RUNTIME_FUNCTIONs.

Contributes to #123124.

src/coreclr/vm/codeman.cpp

eduardo-vp · 2026-03-18T01:20:38Z

Storing in a buffer and flushing with two locks actually led to better performance of the test case mentioned in #123124 (comment).

Change	Time
Main	~580 ms
Buffer + flush with 2 locks	~200 ms

src/coreclr/vm/codeman.cpp

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src/coreclr/vm/codeman.cpp:1

Removal only searches the published table and ignores entries that are still in the pending buffer. If a method is unpublished before its unwind data is flushed, the pending entry can later be published to the OS (stale unwind info), and removal will incorrectly report not found. Fix by also searching/removing matching entries from the pending buffer under s_pUnwindInfoTablePendingLock (and/or forcing a flush before attempting removal) so unpublish is correct regardless of whether the entry was already published.

// Licensed to the .NET Foundation under one or more agreements.

src/coreclr/vm/codeman.cpp

Co-authored-by: Jan Kotas <jkotas@microsoft.com>

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Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

src/coreclr/vm/codeman.cpp

jkotas · 2026-03-20T01:15:19Z

What does the perf look like with the latest delta?

eduardo-vp · 2026-03-20T01:38:21Z

These are the results with the latest changes

Branch	Test execution time
Main	~580 ms
Current	~198 ms

AaronRobinsonMSFT

Two nits I'd personally like to see fix, but other than that, LGTM. Thanks!

src/coreclr/vm/codeman.cpp

Copilot

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

src/coreclr/vm/codeman.cpp

eduardo-vp · 2026-03-20T07:47:38Z

/ba-g unrelated failure

agocke · 2026-03-29T20:59:51Z

/backport to release/10.0

github-actions · 2026-03-29T21:00:00Z

Started backporting to release/10.0 (link to workflow run)

github-actions · 2026-03-29T21:01:52Z

@agocke backporting to release/10.0 failed, the patch most likely resulted in conflicts. Please backport manually!

git am output

$ git am --3way --empty=keep --ignore-whitespace --keep-non-patch changes.patch

Applying: Batch unwind info table entries
Applying: Flush before method is done JITing
Applying: Use two locks
error: sha1 information is lacking or useless (src/coreclr/vm/codeman.cpp).
error: could not build fake ancestor
hint: Use 'git am --show-current-patch=diff' to see the failed patch
hint: When you have resolved this problem, run "git am --continue".
hint: If you prefer to skip this patch, run "git am --skip" instead.
hint: To restore the original branch and stop patching, run "git am --abort".
hint: Disable this message with "git config set advice.mergeConflict false"
Patch failed at 0003 Use two locks
Error: The process '/usr/bin/git' failed with exit code 128

Link to workflow output

agocke · 2026-03-30T20:29:17Z

@eduardo-vp Could you port this over manually? The automation seems to be having issues.

Place the entries of UnwindInfoTable in a buffer and flush such that we amortize the cost of the operations (pRtlAddGrowableFunctionTable + pRtlDeleteGrowableFunctionTable) to create the internal table of `RUNTIME_FUNCTION`s. Contributes to dotnet#123124. --------- Co-authored-by: Eduardo Velarde <evelardepola@microsoft.com> Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com> Co-authored-by: Jan Kotas <jkotas@microsoft.com>

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AaronRobinsonMSFT mentioned this pull request Mar 16, 2026

Fix parallel JIT performance regression: move RtlGrowFunctionTable outside global lock #124680

Closed

Batch unwind info table entries

7358ca6

eduardo-vp force-pushed the lock-per-UnwindInfoTableObject branch from 75cd28d to 7358ca6 Compare March 17, 2026 02:05

jkotas reviewed Mar 17, 2026

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This was referenced Mar 17, 2026

AOT precompile failed on ios-arm64: 'No space left on device' (exit code 1) #125107

Closed

Crst Level violation: Can't take level 17 lock CrstLoaderAllocatorReferences #125638

Closed

Flush before method is done JITing

23fc617

eduardo-vp requested a review from AaronRobinsonMSFT March 17, 2026 19:34

eduardo-vp changed the title ~~Use a lock per UnwindInfoTable object instead of global lock~~ Improve UnwindInfoTable's performance Mar 17, 2026

Use two locks

2d1341c

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Copilot code review

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jkotas reviewed Mar 19, 2026

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Eduardo Velarde added 3 commits March 19, 2026 16:47

Some PR feedback

f0560fd

Remove unnecessary check of the pending buffer when removing unwind info

9db1f73

Take publish lock at the beginning of FlushPendingEntries

8a82cf5

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Free the old table outside the lock

d41ee90

Co-authored-by: Jan Kotas <jkotas@microsoft.com>

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PR feedback

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Co-authored-by: Jan Kotas <jkotas@microsoft.com>

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Nits

84a197a

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eduardo-vp merged commit 43502e5 into dotnet:main Mar 20, 2026
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dotnet-maestro bot mentioned this pull request Mar 21, 2026

[main] Source code updates from dotnet/runtime dotnet/dotnet#5588

Merged

snakefoot mentioned this pull request Mar 29, 2026

Severe performance regression in .NET 10 vs .NET 9 for xUnit v3 test execution #123124

Open

eduardo-vp mentioned this pull request Mar 30, 2026

[release/10.0] Improve UnwindInfoTable's performance #126331

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eduardo-vp commented Mar 14, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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eduardo-vp commented Mar 18, 2026

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eduardo-vp commented Mar 20, 2026

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eduardo-vp commented Mar 14, 2026 •

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