[Feature][Intel XPU] Add memory saver support for Intel XPU via upstream torch_memory_saver

[siju-samuel]

Motivation

Enable release/resume_memory_occupation on Intel XPU using the upstream torch_memory_saver package (Level Zero VMM backend). Replaces in-repo implementation with pip-installable upstream dependency.

Features:

• Pause/resume physical GPU memory while preserving virtual addresses
• Tag-based selective memory management (kv_cache, weights, cuda_graph)
• Optional CPU backup for content preservation
• Multi-device support (verified via the package's multi-device test)
• Sysman-based memory verification (torch accounting doesn't reflect unmapped pages)

Modifications

Changes:

• Add TorchMemorySaverAdapter for unified memory saver API
• XPU uses hook_mode='torch' (in-process pluggable allocator)
• configure_subprocess() and cuda_graph() are no-ops on XPU
• Update Dockerfile to build the upstream package for XPU
• Add test suite (10 tests, all passing)

Installation (XPU builds from source; TMS_PLATFORM=xpu forces the XPU backend and --no-build-isolation lets the build match libsycl to the installed torch):
source /opt/intel/oneapi/setvars.sh
TMS_PLATFORM=xpu pip install --no-build-isolation
git+https://github.com/fzyzcjy/torch_memory_saver.git

Usage:
python -m sglang.launch_server --model-path --device xpu --enable-memory-saver

Depends on: fzyzcjy/torch_memory_saver#78

Accuracy Tests

Speed Tests and Profiling

Checklist

• Format your code according to the Format code with pre-commit.
• Add unit tests according to the Run and add unit tests.
• Update documentation according to Write documentations.
• Provide accuracy and speed benchmark results according to [Test the accuracy] (https://docs.sglang.io/developer_guide/contribution_guide.html#test-the-accuracy) and Benchmark the speed. N/A
• Follow the SGLang code style guidance.

Review and Merge Process

1. Ping Merge Oncalls to start the process. See the PR Merge Process.
2. Get approvals from CODEOWNERS and other reviewers.
3. Trigger CI tests with comments or contact authorized users to do so.
   • Common commands include /tag-and-rerun-ci, /tag-run-ci-label, /rerun-failed-ci
4. After green CI and required approvals, ask Merge Oncalls or people with Write permission to merge the PR.

cc @mingfeima @fzyzcjy @habaohaba @yueming-yuan @jianan-gu @hnyls2002 @merrymercy

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CI States

Latest PR Test (Base): ❌ Run #34083643346
Latest PR Test (Extra): ❌ Run #34083643187
Latest PR Test (AMD ROCm 7.2): ❌ Run #34083643322

[gemini-code-assist]

Code Review

This pull request adds support for the experimental Memory Saver feature on Intel XPU, allowing the engine to temporarily release and reclaim GPU memory. The changes include updating the Dockerfile to install torch_memory_saver from source, adding documentation, adapting the TorchMemorySaverAdapter for XPU specifics (such as using the in-process pluggable allocator), updating memory utility functions, and introducing a comprehensive suite of unit tests. The reviewer feedback suggests pinning the torch_memory_saver repository to a specific commit hash in the Dockerfile to ensure reproducible builds, and removing an unused variable cur in the test setup.

Important

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[polisettyvarma]

why can't we support this ?

[siju-samuel]

/tag-run-ci-label

[mingfeima]

https://github.com/sgl-project/sglang/actions/runs/32100083362/job/95598837541 xpu ci failed. seems to be related to this pr, where torch_memory_saver import in torch_memory_saver_adapter.py:L7-L20, even without --enable-memory-saver.

please check.