Files
blightbow 67baf66555 feat(mlx): add thread-safe LRU prompt cache and min_p/top_k sampling (#7556)
* feat(mlx): add thread-safe LRU prompt cache

Port mlx-lm's LRUPromptCache to fix race condition where concurrent
requests corrupt shared KV cache state. The previous implementation
used a single prompt_cache instance shared across all requests.

Changes:
- Add backend/python/common/mlx_cache.py with ThreadSafeLRUPromptCache
- Modify backend.py to use per-request cache isolation via fetch/insert
- Add prefix matching for cache reuse across similar prompts
- Add LRU eviction (default 10 entries, configurable)
- Add concurrency and cache unit tests

The cache uses a trie-based structure for efficient prefix matching,
allowing prompts that share common prefixes to reuse cached KV states.
Thread safety is provided via threading.Lock.

New configuration options:
- max_cache_entries: Maximum LRU cache entries (default: 10)
- max_kv_size: Maximum KV cache size per entry (default: None)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Signed-off-by: Blightbow <blightbow@users.noreply.github.com>

* feat(mlx): add min_p and top_k sampler support

Add MinP field to proto (field 52) following the precedent set by
other non-OpenAI sampling parameters like TopK, TailFreeSamplingZ,
TypicalP, and Mirostat.

Changes:
- backend.proto: Add float MinP field for min-p sampling
- backend.py: Extract and pass min_p and top_k to mlx_lm sampler
  (top_k was in proto but not being passed)
- test.py: Fix test_sampling_params to use valid proto fields and
  switch to MLX-compatible model (mlx-community/Llama-3.2-1B-Instruct)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Signed-off-by: Blightbow <blightbow@users.noreply.github.com>

* refactor(mlx): move mlx_cache.py from common to mlx backend

The ThreadSafeLRUPromptCache is only used by the mlx backend. After
evaluating mlx-vlm, it was determined that the cache cannot be shared
because mlx-vlm's generate/stream_generate functions don't support
the prompt_cache parameter that mlx_lm provides.

- Move mlx_cache.py from backend/python/common/ to backend/python/mlx/
- Remove sys.path manipulation from backend.py and test.py
- Fix test assertion to expect "MLX model loaded successfully"

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Signed-off-by: Blightbow <blightbow@users.noreply.github.com>

* test(mlx): add comprehensive cache tests and document upstream behavior

Added comprehensive unit tests (test_mlx_cache.py) covering all cache
operation modes:
- Exact match
- Shorter prefix match
- Longer prefix match with trimming
- No match scenarios
- LRU eviction and access order
- Reference counting and deep copy behavior
- Multi-model namespacing
- Thread safety with data integrity verification

Documents upstream mlx_lm/server.py behavior: single-token prefixes are
deliberately not matched (uses > 0, not >= 0) to allow longer cached
sequences to be preferred for trimming. This is acceptable because real
prompts with chat templates are always many tokens.

Removed weak unit tests from test.py that only verified "no exception
thrown" rather than correctness.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Signed-off-by: Blightbow <blightbow@users.noreply.github.com>

* chore(mlx): remove unused MinP proto field

The MinP field was added to PredictOptions but is not populated by the
Go frontend/API. The MLX backend uses getattr with a default value,
so it works without the proto field.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Signed-off-by: Blightbow <blightbow@users.noreply.github.com>

---------

Signed-off-by: Blightbow <blightbow@users.noreply.github.com>
Co-authored-by: Blightbow <blightbow@users.noreply.github.com>
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
2025-12-16 11:27:46 +01:00
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2025-08-22 08:42:29 +02:00
2025-08-22 08:42:29 +02:00
2025-08-22 08:42:29 +02:00
2025-08-22 08:42:29 +02:00