common: add intrusive list

[wbpcode]

Commit Message: common: add intrusive list
Additional Description:

In the current implementation, the LinkedObject and std::list is widely used to store the linked heap object. But we will find although we use the LinkedObject to invade the heap object, but because std::list is used, we still always need to allocated a heap list node for every stored heap object.

This PR added an implementation of intrusive linked list which could be used to replace the std::list + LinkedObject and get better efficiency and eliminate unnecessary heap allocations.

Risk Level: low. Only new container implementation and does not change any existing feature.
Testing: unit.
Docs Changes: n/a.
Release Notes: n/a.
Platform Specific Features: n/a.

[wbpcode]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces a well-implemented intrusive linked list (IntrusiveList and IntrusiveListNode) as a more efficient alternative to std::list with LinkedObject. The implementation is solid, with clear ownership semantics and good test coverage. My feedback focuses on refining the API to be more idiomatic and robust.

[Copilot]

Pull request overview

Adds a new intrusive, owning doubly-linked list implementation alongside the existing LinkedObject helpers, aiming to avoid per-element std::list node allocations and improve locality for linked heap objects.

Changes:

• Introduces IntrusiveListNode<T> (CRTP) and IntrusiveList<T> into source/common/common/linked_object.h.
• Adds unit tests covering insert/remove and cross-list moves for the new intrusive list.

Reviewed changes

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

File	Description
source/common/common/linked_object.h	Adds the new intrusive list/node container implementation.
test/common/common/linked_object_test.cc	Adds unit tests for intrusive list insertion/removal and moving between lists.

---

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[wbpcode]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces a well-designed and thoroughly documented intrusive list implementation, IntrusiveList and IntrusiveListNode. This is a valuable addition that promises performance benefits by eliminating extra memory allocations compared to std::list<unique_ptr<T>>. The implementation is robust, featuring clear ownership semantics and compile-time safety checks. The unit tests are comprehensive, covering a wide range of scenarios. My feedback includes a couple of minor suggestions to improve the clarity of compile-time error messages.

[Copilot]

Pull request overview

Adds a new owning intrusive doubly-linked list implementation to source/common/common/linked_object.h, intended to avoid the per-element std::list node allocation currently incurred by std::list<std::unique_ptr<T>> patterns, and extends the existing unit tests to cover the new container behavior.

Changes:

• Introduce IntrusiveListNode<T> (CRTP) and IntrusiveList<T> (owning container) in linked_object.h.
• Add unit tests validating push front/back, removal in different positions, and moving elements between lists.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 6 comments.

File	Description
source/common/common/linked_object.h	Adds IntrusiveListNode + IntrusiveList implementation and documentation.
test/common/common/linked_object_test.cc	Adds unit tests covering the new intrusive list APIs.

---

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[wbpcode]

retest

[wbpcode]

/retest

[paul-r-gall]

Do you by any chance have benchmarks for this?

[repokitteh-read-only]

yavlasov cannot be assigned to this issue.

🐱

Caused by: a #43967 (comment) was created by @paul-r-gall.

see: more, trace.

[repokitteh-read-only]

🙀 Error while processing event:

evaluation error
error: function _github_call error: github error: POST https://api.github.com/repos/envoyproxy/envoy/issues/comments/4067553496/reactions: 404 Not Found []:
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  bootstrap:143: in <toplevel>
  bootstrap:135: in _main
  bootstrap:62: in _call
  bootstrap:15: in _call1
  github.com/repokitteh/modules/assign.star:21: in _assign
  github.com/repokitteh/modules/lib/utils.star:11: in react
  github:784: in issue_create_comment_reaction
  github:155: in call
Error: function _github_call error: github error: POST https://api.github.com/repos/envoyproxy/envoy/issues/comments/4067553496/reactions: 404 Not Found []

🐱

Caused by: a #43967 (comment) was created by @paul-r-gall.

see: more, trace.

[paul-r-gall]

/assign @yanavlasov

[wbpcode]

Do you by any chance have benchmarks for this?

Sure, Paul. Here is a result of the benchmark:

------------------------------------------------------------------------
Benchmark                              Time             CPU   Iterations
------------------------------------------------------------------------
BM_StdListPushFront/64               815 ns          815 ns       801049
BM_StdListPushFront/512             6444 ns         6444 ns       108817
BM_StdListRemoveAll/64               578 ns          578 ns      1211095
BM_StdListRemoveAll/512             3876 ns         3876 ns       180172
BM_StdListIterate/64                37.9 ns         37.9 ns     18506186
BM_StdListIterate/512                376 ns          376 ns      1857998
BM_IntrusiveListPushFront/64         417 ns          417 ns      1678990
BM_IntrusiveListPushFront/512       3252 ns         3252 ns       214056
BM_IntrusiveListRemoveAll/64         353 ns          353 ns      1986929
BM_IntrusiveListRemoveAll/512       2044 ns         2044 ns       342375
BM_IntrusiveListIterate/64          30.1 ns         30.1 ns     23278029
BM_IntrusiveListIterate/512          363 ns          363 ns      1925743

From the result, we can found the new intrusive list have similar iteration performance. And have ~50% improvement for insertion and removal. Sure this is before we used very simple heap object for test. If more complex structure are used, I guess there won't be such huge improvement.

[wbpcode]

/retest