add memtrace use Kconfig

[greenfool]

修改文档.pdf

[cebarobot]

Hi, thanks for your PR. This is a nice idea to improve our checkpoint flow. But there is still some issues that should be fixed before merging this PR.

1. Could you please add an PR description (and commit message) in English? Your PDF file is nice, but may be not suitable for a PR.
2. Could you please add an description in OpenXiangShan/XiangShan-doc? The motivation and result part of your PDF may be moved to there.
3. There is some problems in your codes. I'll point it out later.

For your contribution, I also have some questions:

1. I'm not sure whether your test results is strong enough to persuade us to switch to your way. Could you try to run more test programs?
2. Is CacheReplay a boot program like gcptRestorer? How does it works? Can it work on normal simulation environments, like XiangShan's verilator/pldm emulator? Why do you need to modify GEM5?

[greenfool]

Hi ,thanks for your valuable feedback and recognition of the PR! I totally agree with all your suggestions and will address each point promptly:

1. PR Description & Commit Message

I’ll add a detailed English description to the PR (including key changes, design logic, and compatibility notes) and update all commit messages to follow the English convention. This will be completed within next week.

2. XiangShan-doc Update

I’ll migrate the "Motivation" and "Experimental Results" sections from the PDF to OpenXiangShan/XiangShan-doc (under the appropriate directory). I’ll ensure the content is concise, structured, and aligned with the doc’s existing style. Will share the doc PR link for your review once ready.

3. Code Issues

No problem! Please feel free to point out the specific code issues – I’ll fix them immediately and add corresponding test cases to avoid regressions.

4. Test Results Enhancement

I fully understand the need for stronger validation. I’ll try to expand the test suite.

5. Questions About CacheReplay

• Is CacheReplay a boot program like gcptRestorer?

  No – CacheReplay is a standalone program, distinct from gcptRestorer. It first generates the microarchitectural state of the cache hierarchy for the corresponding checkpoints under different configurations by parsing and simulating the memtrace. Then, during checkpoint restoration in GEM5, it constructs the exact microarchitectural state of the cache hierarchy using this information, instead of relying on warm-up instructions.

• How does it work?

  First, in NEMU, we capture all memory accesses during execution and generate a memtrace . CacheReplay then reads this memtrace and runs simulations in accordance with specified cache configurations; through this simulation, it derives the exact cache microstate (including cache data, tags, LRU timestamps, and more) that the cache hierarchy should be in when restoring the target checkpoint under the given configurations. Finally, it outputs all these microstate details to a dedicated file. During checkpoint restoration in GEM5, the system reads this pre-generated microstate file and reconstructs the cache hierarchy’s state exactly as required based on the file’s information.

• Compatibility with Verilator/PLDM emulator?

  Currently, this implementation only runs on the XiangShan-specific GEM5 emulator and has not yet been tested on the Verilator or PLDM emulators.

• Why modify GEM5?

  GEM5 does not natively support the restoration of cache microarchitectural states. To allow GEM5 to read the output file from CacheReplay and restore the corresponding cache microarchitectural state, we need to add a set of additional behaviors to GEM5’s checkpoint restoration process. Importantly, this modification is fully controlled by dedicated configuration options and will not impact any of GEM5’s original functionalities or existing checkpoint workflows.

Thanks again for your guidance!