From cf76b0447a633f78ebba6053ba7ed1df539bc7ab Mon Sep 17 00:00:00 2001
From: Rattus <rattus128@gmail.com>
Date: Tue, 27 Jan 2026 14:19:07 +1000
Subject: [PATCH] mm: redefine free memory for Windows

As commented.
---
 comfy/model_management.py |  8 +++++-
 comfy/windows.py          | 52 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 59 insertions(+), 1 deletion(-)
 create mode 100644 comfy/windows.py

diff --git a/comfy/model_management.py b/comfy/model_management.py
index 412752503..804be7768 100644
--- a/comfy/model_management.py
+++ b/comfy/model_management.py
@@ -585,9 +585,15 @@ WINDOWS = any(platform.win32_ver())
 
 EXTRA_RESERVED_VRAM = 400 * 1024 * 1024
 if WINDOWS:
+    import comfy.windows
     EXTRA_RESERVED_VRAM = 600 * 1024 * 1024 #Windows is higher because of the shared vram issue
     if total_vram > (15 * 1024):  # more extra reserved vram on 16GB+ cards
         EXTRA_RESERVED_VRAM += 100 * 1024 * 1024
+    def get_free_ram():
+        return comfy.windows.get_free_ram()
+else:
+    def get_free_ram():
+        return psutil.virtual_memory().available
 
 if args.reserve_vram is not None:
     EXTRA_RESERVED_VRAM = args.reserve_vram * 1024 * 1024 * 1024
@@ -618,7 +624,7 @@ def free_memory(memory_required, device, keep_loaded=[], for_dynamic=False, ram_
         ram_to_free = 1e32
         if not DISABLE_SMART_MEMORY:
             memory_to_free = memory_required - get_free_memory(device)
-            ram_to_free = ram_required - psutil.virtual_memory().available
+            ram_to_free = ram_required - get_free_ram()
 
         if current_loaded_models[i].model.is_dynamic() and for_dynamic:
             #don't actually unload dynamic models for the sake of other dynamic models
diff --git a/comfy/windows.py b/comfy/windows.py
new file mode 100644
index 000000000..213dc481d
--- /dev/null
+++ b/comfy/windows.py
@@ -0,0 +1,52 @@
+import ctypes
+import logging
+import psutil
+from ctypes import wintypes
+
+import comfy_aimdo.control
+
+psapi = ctypes.WinDLL("psapi")
+kernel32 = ctypes.WinDLL("kernel32")
+
+class PERFORMANCE_INFORMATION(ctypes.Structure):
+    _fields_ = [
+        ("cb", wintypes.DWORD),
+        ("CommitTotal", ctypes.c_size_t),
+        ("CommitLimit", ctypes.c_size_t),
+        ("CommitPeak", ctypes.c_size_t),
+        ("PhysicalTotal", ctypes.c_size_t),
+        ("PhysicalAvailable", ctypes.c_size_t),
+        ("SystemCache", ctypes.c_size_t),
+        ("KernelTotal", ctypes.c_size_t),
+        ("KernelPaged", ctypes.c_size_t),
+        ("KernelNonpaged", ctypes.c_size_t),
+        ("PageSize", ctypes.c_size_t),
+        ("HandleCount", wintypes.DWORD),
+        ("ProcessCount", wintypes.DWORD),
+        ("ThreadCount", wintypes.DWORD),
+    ]
+
+def get_free_ram():
+    #Windows is way too conservative and chalks recently used uncommitted model RAM
+    #as "in-use". So, calculate free RAM for the sake of general use as the greater of:
+    #
+    #1: What psutil says
+    #2: Total Memory - (Committed Memory - VRAM in use)
+    #
+    #We have to subtract VRAM in use from the comitted memory as WDDM creates a naked
+    #commit charge for all VRAM used just incase it wants to page it all out. This just
+    #isn't realistic so "overcommit" on our calculations by just subtracting it off.
+
+    pi = PERFORMANCE_INFORMATION()
+    pi.cb = ctypes.sizeof(pi)
+
+    if not psapi.GetPerformanceInfo(ctypes.byref(pi), pi.cb):
+        logging.warning("WARNING: Failed to query windows performance info. RAM usage may be sub optimal")
+        return psutil.virtual_memory().available
+
+    committed = pi.CommitTotal * pi.PageSize
+    total = pi.PhysicalTotal * pi.PageSize
+
+    return max(psutil.virtual_memory().available,
+               total - (committed - comfy_aimdo.control.get_total_vram_usage()))
+