[1/4] Bitmap for L2 storage in MP mode by ApostaC · Pull Request #2563 · LMCache/LMCache

ApostaC · 2026-02-07T00:23:56Z

What this PR does / why we need it:

Part of #2562

Special notes for your reviewers:

If applicable:

this PR contains user facing changes - docs added
this PR contains unit tests

Signed-off-by: ApostaC <yihua98@uchicago.edu>

gemini-code-assist · 2026-02-07T00:24:13Z

Summary of Changes

Hello @ApostaC, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a fundamental C++ Bitmap utility class designed for efficient bit-level tracking, specifically intended for managing the state of L2 storage operations within a multi-process environment. The implementation includes methods for setting, clearing, testing individual bits, and performing advanced bit counting operations like popcount, clz, and clo, along with bitwise AND. To facilitate its use across the system, the Bitmap class is seamlessly integrated with Python through pybind11 bindings. The changes are accompanied by a thorough suite of unit tests to validate the correctness and robustness of the new bitmap functionality.

Highlights

New Bitmap Class: A new C++ Bitmap class has been introduced to efficiently track the state of L2 storage operation results, providing core bit manipulation functionalities.
Python Bindings: The new Bitmap class is exposed to Python via pybind11, allowing Python-based components to utilize its functionalities.
Comprehensive Unit Tests: Extensive unit tests have been added for the Bitmap class using pytest, covering various scenarios including bit setting, clearing, counting, and bitwise operations, especially for sizes not multiples of 8.
Build System Integration: The setup.py script has been updated to include the new bitmap.cpp source file in both CUDA and ROCm extensions, ensuring proper compilation and linking.

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Changelog

csrc/storage_manager/bitmap.cpp
- Added a new C++ source file implementing the Bitmap class.
- Implemented methods for set, clear, test, popcount, clz (count leading zeros), clo (count leading ones), bitwise AND (operator&), and to_string conversion.
csrc/storage_manager/bitmap.h
- Added a new header file defining the Bitmap class interface with Doxygen-style comments for clarity.
csrc/storage_manager/pybind.cpp
- Included the new bitmap.h header.
- Added using lmcache::storage_manager::Bitmap;.
- Exposed the Bitmap class and its methods to Python using pybind11, including constructor, set, clear, test, popcount, count_leading_zeros, count_leading_ones, __and__, and __repr__.
setup.py
- Updated storage_manager_sources in both cuda_extension and rocm_extension functions to include csrc/storage_manager/bitmap.cpp for compilation.
tests/v1/multiprocess/test_bitmap.py
- Added a new Python unit test file for the Bitmap class using pytest.
- Included tests for set, clear, test operations across various bitmap sizes.
- Added tests for popcount to verify correct counting of set bits.
- Implemented tests for clz and clo functionalities.
- Provided tests for bitwise AND operations, including scenarios with different bitmap sizes.
- Added tests for the to_string representation of the bitmap.
- Included specific tests to ensure correct behavior for bitmaps whose sizes are not multiples of 8.

Activity

This pull request is part of a larger effort tracked by issue Support L2 storage in MP mode #2562.
No human activity (comments, reviews, etc.) has been recorded yet for this pull request.

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Code Review

This pull request introduces a Bitmap class to support L2 storage in multiprocess mode, complete with C++ implementation, pybind11 bindings, and unit tests. A critical integer overflow vulnerability was identified in the Bitmap constructor's memory allocation logic, which can lead to out-of-bounds memory access and denial-of-service conditions for large bitmap sizes. Additionally, the review suggests improvements for C++ maintainability and performance, including refactoring complex functions and optimizing a string conversion method, and strengthening assertions in the Python tests.

Signed-off-by: ApostaC <yihua98@uchicago.edu>

Signed-off-by: Yihua Cheng <yihua98@uchicago.edu>

Signed-off-by: ApostaC <yihua98@uchicago.edu>

KuntaiDu

Code is straightforward for me.

ApostaC · 2026-02-26T18:46:21Z

Going to merge this as we discussed offline.

* [add] bitmap module Signed-off-by: ApostaC <yihua98@uchicago.edu> * adjust the cpp implementation and add pyi tests Signed-off-by: ApostaC <yihua98@uchicago.edu>

* [add] bitmap module Signed-off-by: ApostaC <yihua98@uchicago.edu> * adjust the cpp implementation and add pyi tests Signed-off-by: ApostaC <yihua98@uchicago.edu> Signed-off-by: Ofer Kiselov Nahman <ofer.kiselovnahman@weka.io>

* [add] bitmap module Signed-off-by: ApostaC <yihua98@uchicago.edu> * adjust the cpp implementation and add pyi tests Signed-off-by: ApostaC <yihua98@uchicago.edu>

* [add] bitmap module Signed-off-by: ApostaC <yihua98@uchicago.edu> * adjust the cpp implementation and add pyi tests Signed-off-by: ApostaC <yihua98@uchicago.edu> Signed-off-by: shaoxiawjc <wjc2800@163.com>

* [add] bitmap module Signed-off-by: ApostaC <yihua98@uchicago.edu> * adjust the cpp implementation and add pyi tests Signed-off-by: ApostaC <yihua98@uchicago.edu> Signed-off-by: Aaron Wu <aaron.wu@dell.com>

[add] bitmap module

18d0c40

Signed-off-by: ApostaC <yihua98@uchicago.edu>

gemini-code-assist Bot reviewed Feb 7, 2026

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ApostaC mentioned this pull request Feb 7, 2026

Support L2 storage in MP mode #2562

Closed

8 tasks

ApostaC added 2 commits February 8, 2026 15:29

Merge branch 'dev' into local-dev/l2-adapter-1

f8d7be8

adjust the cpp implementation and add pyi tests

4a3d233

Signed-off-by: ApostaC <yihua98@uchicago.edu>

ApostaC requested review from KuntaiDu and YaoJiayi February 9, 2026 01:02

ApostaC added the full Run comprehensive tests on this PR label Feb 9, 2026

ApostaC mentioned this pull request Feb 9, 2026

[2/4] L2Adapter interface and implementation of MockL2Adapter #2569

Merged

2 tasks

KuntaiDu reviewed Feb 25, 2026

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Comment thread csrc/storage_manager/bitmap.cpp

KuntaiDu reviewed Feb 25, 2026

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Comment thread csrc/storage_manager/bitmap.cpp

ApostaC added 2 commits February 25, 2026 17:27

Merge branch 'dev' into local-dev/l2-adapter-1

4906a72

Signed-off-by: Yihua Cheng <yihua98@uchicago.edu>

fix precommit

33296db

Signed-off-by: ApostaC <yihua98@uchicago.edu>

KuntaiDu approved these changes Feb 26, 2026

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ApostaC merged commit 743c5a7 into LMCache:dev Feb 26, 2026
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[1/4] Bitmap for L2 storage in MP mode #2563

[1/4] Bitmap for L2 storage in MP mode #2563
ApostaC merged 5 commits intoLMCache:devfrom
ApostaC:local-dev/l2-adapter-1

ApostaC commented Feb 7, 2026

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ApostaC commented Feb 7, 2026

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ApostaC commented Feb 26, 2026

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