[BugFix] Fix GC bug for `LLM` class (#2882)

tests/test_regression.py

@@ -4,6 +4,10 @@ It should include tests that are reported by users and making sure they
 will never happen again.
 
 """
+import gc
+
+import torch
+
 from vllm import LLM, SamplingParams
 
 
@@ -35,6 +39,20 @@ def test_max_tokens_none():
     assert len(prompts) == len(outputs)
 
 
+def test_gc():
+    llm = LLM("facebook/opt-125m", enforce_eager=True)
+    del llm
+
+    gc.collect()
+    torch.cuda.empty_cache()
+
+    # The memory allocated for model and KV cache should be released.
+    # The memory allocated for PyTorch and others should be less than 50MB.
+    # Usually, it's around 10MB.
+    allocated = torch.cuda.memory_allocated()
+    assert allocated < 50 * 1024 * 1024
+
+
 if __name__ == "__main__":
     import pytest
     pytest.main([__file__])

vllm/lora/punica.py

@@ -4,23 +4,26 @@ from typing import Optional
 
 import torch
 
-import_exc = None
 
-try:
-    import vllm._punica_C as punica_kernels
-except ImportError as e:
-    import_exc = e
+def _raise_import_error(e):
+    if torch.cuda.get_device_capability() < (8, 0):
+        raise ImportError(
+            "punica LoRA kernels require compute capability >= 8.0") from e
+    else:
+        raise ImportError(
+            "punica LoRA kernels could not be imported. If you built vLLM "
+            "from source, make sure VLLM_INSTALL_PUNICA_KERNELS=1 env var "
+            "was set.") from e
 
-if import_exc is None:
 
-    def bgmv(
+def bgmv(
     y: torch.Tensor,
     x: torch.Tensor,
     w_t_all: torch.Tensor,
     indicies: torch.LongTensor,
     layer_idx: int,
     scale: float,
-    ):
+):
     """
     Semantics:
       y[i] += (
@@ -38,9 +41,15 @@ if import_exc is None:
       layer_idx: Layer index of the weight matrices.
       scale: Scaling factor.
     """
+    try:
+        import vllm._punica_C as punica_kernels
+    except ImportError as e:
+        _raise_import_error(e)
+
     punica_kernels.dispatch_bgmv(y, x, w_t_all, indicies, layer_idx, scale)
 
-    def add_lora(y: torch.Tensor,
+
+def add_lora(y: torch.Tensor,
              x: torch.Tensor,
              wa_t_all: torch.Tensor,
              wb_t_all: torch.Tensor,
@@ -70,6 +79,11 @@ if import_exc is None:
       scale: Scaling factor.
       buffer: Optional. Shape: `[B, R]`. Temporary buffer.
     """
+    try:
+        import vllm._punica_C as punica_kernels
+    except ImportError as e:
+        _raise_import_error(e)
+
     r = wb_t_all.size(-1)
     if buffer is None:
         # We set the buffer to be float32 by default to avoid
@@ -78,12 +92,12 @@ if import_exc is None:
         buffer = torch.zeros((x.size(0), r),
                              dtype=torch.float32,
                              device=x.device)
-        punica_kernels.dispatch_bgmv(buffer, x, wa_t_all, indicies, layer_idx,
-                                     1.0)
+    punica_kernels.dispatch_bgmv(buffer, x, wa_t_all, indicies, layer_idx, 1.0)
     punica_kernels.dispatch_bgmv(y, buffer, wb_t_all, indicies, layer_idx,
                                  scale)
 
-    def add_lora_slice(y: torch.Tensor,
+
+def add_lora_slice(y: torch.Tensor,
                    x: torch.Tensor,
                    wa_t_all: torch.Tensor,
                    wb_t_all: torch.Tensor,
@@ -119,6 +133,11 @@ if import_exc is None:
       y_offset: Offset to apply to the starting column of y.
       y_slice_size: Size of the y column slice.
     """
+    try:
+        import vllm._punica_C as punica_kernels
+    except ImportError as e:
+        _raise_import_error(e)
+
     r = wb_t_all.size(-1)
     if buffer is None:
         # We set the buffer to be float32 by default to avoid
@@ -149,28 +168,3 @@ if import_exc is None:
         y_slice_size,
         y_offset,
     )
-
-else:
-
-    def _raise_exc(
-        *args,  # pylint: disable=unused-argument
-        **kwargs  # pylint: disable=unused-argument
-    ):
-        if torch.cuda.get_device_capability() < (8, 0):
-            raise ImportError("punica LoRA kernels require compute "
-                              "capability>=8.0") from import_exc
-        else:
-            raise ImportError(
-                "punica LoRA kernels could not be imported. If you built vLLM "
-                "from source, make sure VLLM_INSTALL_PUNICA_KERNELS=1 env var "
-                "was set.") from import_exc
-
-    bgmv = _raise_exc
-    add_lora = _raise_exc
-    add_lora_slice = _raise_exc
-
-__all__ = [
-    "bgmv",
-    "add_lora",
-    "add_lora_slice",
-]