fixing vllm.

amdsmi-shim/strixhalo_vram_fix.py

@@ -1,22 +1,28 @@
 """
-Monkey-patch torch.cuda.mem_get_info for AMD APUs with unified memory.
+Monkey-patch torch.cuda memory reporting for AMD APUs with unified memory.
 
-On Strix Halo (and other AMD APUs), torch.cuda.mem_get_info() returns
-GTT (system RAM accessible to GPU) numbers instead of actual VRAM:
-  - Total:  128 GiB  (GTT pool, NOT real VRAM)
-  - Free:    29 GiB  (GTT free, NOT VRAM free)
+On Strix Halo (and other AMD APUs), PyTorch reports GTT (system RAM
+accessible to GPU) instead of actual VRAM:
+
+  torch.cuda.mem_get_info()              → (29 GiB free, 128 GiB total)  WRONG
+  torch.cuda.get_device_properties().total_memory → 128 GiB              WRONG
 
 Meanwhile sysfs reports the real VRAM:
-  - Total:  96 GiB   (actual dedicated VRAM from BIOS)
-  - Free:   95.8 GiB (actual VRAM free)
+  /sys/class/drm/cardN/device/mem_info_vram_total → 96 GiB
+  /sys/class/drm/cardN/device/mem_info_vram_used  → ~0.2 GiB
 
-vLLM uses torch.cuda.mem_get_info() to calculate how much memory to
-pre-allocate.  With wrong numbers it either OOMs or refuses to start.
+vLLM uses mem_get_info() and get_device_properties() to decide how much
+memory to pre-allocate. With wrong numbers it either OOMs or refuses to
+start ("Free memory less than desired GPU memory utilization").
 
-This module patches mem_get_info to return sysfs VRAM values, which
-are the physically meaningful numbers for allocation decisions.
+This module patches both APIs to return sysfs VRAM values instead.
 
 Installed as a .pth hook so it runs before any user code.
+
+IMPORTANT: The re-entry guard (_STRIXHALO_VRAM_FIX_ACTIVE env var) is
+set only during torch import to prevent infinite recursion when torch
+spawns offload-arch. It is CLEARED afterward so child processes (e.g.
+vLLM EngineCore subprocesses) can apply their own patch.
 """
 
 import os
@@ -63,6 +69,8 @@ def _should_skip() -> bool:
     # Re-entry guard: importing torch triggers subprocess calls to
     # offload-arch (a Python script), which re-enters this .pth hook.
     # Without this guard it creates an infinite fork bomb.
+    # NOTE: This is only set transiently during _apply_patch() and
+    # cleared afterward — child processes will NOT see it.
     if os.environ.get(_GUARD_ENV):
         return True
 
@@ -83,8 +91,31 @@ def _should_skip() -> bool:
     return False
 
 
+class _VRAMDeviceProperties:
+    """Proxy that overrides total_memory on torch device properties."""
+
+    def __init__(self, original, vram_total: int):
+        object.__setattr__(self, "_original", original)
+        object.__setattr__(self, "_vram_total", vram_total)
+
+    @property
+    def total_memory(self) -> int:
+        return object.__getattribute__(self, "_vram_total")
+
+    def __getattr__(self, name: str):
+        return getattr(object.__getattribute__(self, "_original"), name)
+
+    def __repr__(self) -> str:
+        orig = object.__getattribute__(self, "_original")
+        vram = object.__getattribute__(self, "_vram_total")
+        return repr(orig).replace(
+            f"total_memory={orig.total_memory}",
+            f"total_memory={vram}",
+        )
+
+
 def _apply_patch() -> None:
-    """Patch torch.cuda.mem_get_info if we detect unified memory mis-reporting."""
+    """Patch torch.cuda memory APIs if we detect unified memory mis-reporting."""
     if _should_skip():
         return
 
@@ -101,13 +132,18 @@ def _apply_patch() -> None:
             return
     except ImportError:
         return
+    finally:
+        # CRITICAL: Clear the guard so child processes (vLLM EngineCore
+        # subprocesses, Ray actor workers, etc.) can apply their own patch.
+        # The guard only needs to live during the torch import above to
+        # prevent the offload-arch → .pth → torch import recursion.
+        os.environ.pop(_GUARD_ENV, None)
 
     vram_info = _get_real_vram()
     if vram_info is None:
         return
 
     vram_total, vram_used = vram_info
-    vram_free = vram_total - vram_used
 
     # Only patch if PyTorch total differs significantly from sysfs VRAM
     # (i.e. PyTorch is reporting GTT/unified memory, not real VRAM)
@@ -120,13 +156,14 @@ def _apply_patch() -> None:
     if abs(pt_total - vram_total) / max(pt_total, 1) < 0.10:
         return
 
-    original_fn = torch.cuda.mem_get_info
+    # --- Patch 1: torch.cuda.mem_get_info ---
+    original_mem_get_info = torch.cuda.mem_get_info
 
     def _patched_mem_get_info(device=None):
         """Return real VRAM from sysfs instead of GTT numbers."""
         real = _get_real_vram()
         if real is None:
-            return original_fn(device)
+            return original_mem_get_info(device)
         total, used = real
         # Account for PyTorch's own allocations on top of sysfs baseline
         pt_allocated = torch.cuda.memory_allocated(device or 0)
@@ -134,9 +171,25 @@ def _apply_patch() -> None:
         return (max(free, 0), total)
 
     torch.cuda.mem_get_info = _patched_mem_get_info
+
+    # --- Patch 2: torch.cuda.get_device_properties ---
+    # total_memory is a read-only C property, so we wrap the return value
+    # in a proxy that overrides it with the real VRAM total.
+    original_get_device_properties = torch.cuda.get_device_properties
+
+    def _patched_get_device_properties(device=None):
+        props = original_get_device_properties(device)
+        real = _get_real_vram()
+        if real is None:
+            return props
+        return _VRAMDeviceProperties(props, real[0])
+
+    torch.cuda.get_device_properties = _patched_get_device_properties
+
     logger.info(
-        "strixhalo_vram_fix: patched torch.cuda.mem_get_info "
-        "(PyTorch reported %d GiB total, sysfs VRAM is %d GiB)",
+        "strixhalo_vram_fix: patched torch.cuda.mem_get_info and "
+        "get_device_properties (PyTorch reported %d GiB total, "
+        "sysfs VRAM is %d GiB)",
         pt_total // (1024**3),
         vram_total // (1024**3),
     )