Fix Intel GPU memory allocation accuracy and documentation update. (#3459)

* Change calculation of memory total to be more accurate, allocated is actually smaller than reserved.

* Update README.md install documentation for Intel GPUs.

README.md

@@ -136,7 +136,16 @@ After this you should have everything installed and can proceed to running Comfy
 
 ### Others:
 
-#### [Intel Arc](https://github.com/comfyanonymous/ComfyUI/discussions/476)
+#### Intel GPUs
+
+Intel GPU support is available for all Intel GPUs supported by Intel's Extension for Pytorch (IPEX) with the support requirements listed in the [Installation](https://intel.github.io/intel-extension-for-pytorch/index.html#installation?platform=gpu) page. Choose your platform and method of install and follow the instructions. The steps are as follows:
+
+1. Start by installing the drivers or kernel listed or newer in the Installation page of IPEX linked above for Windows and Linux if needed.
+1. Follow the instructions to install [Intel's oneAPI Basekit](https://www.intel.com/content/www/us/en/developer/tools/oneapi/base-toolkit-download.html) for your platform.
+1. Install the packages for IPEX using the instructions provided in the Installation page for your platform.
+1. Follow the [ComfyUI manual installation](#manual-install-windows-linux) instructions for Windows and Linux and run ComfyUI normally as described above after everything is installed.
+
+Additional discussion and help can be found [here](https://github.com/comfyanonymous/ComfyUI/discussions/476).
 
 #### Apple Mac silicon
 

comfy/model_management.py

@@ -102,8 +102,8 @@ def get_total_memory(dev=None, torch_total_too=False):
         elif is_intel_xpu():
             stats = torch.xpu.memory_stats(dev)
             mem_reserved = stats['reserved_bytes.all.current']
-            mem_total = torch.xpu.get_device_properties(dev).total_memory
             mem_total_torch = mem_reserved
+            mem_total = torch.xpu.get_device_properties(dev).total_memory
         else:
             stats = torch.cuda.memory_stats(dev)
             mem_reserved = stats['reserved_bytes.all.current']
@@ -701,10 +701,10 @@ def get_free_memory(dev=None, torch_free_too=False):
         elif is_intel_xpu():
             stats = torch.xpu.memory_stats(dev)
             mem_active = stats['active_bytes.all.current']
-            mem_allocated = stats['allocated_bytes.all.current']
             mem_reserved = stats['reserved_bytes.all.current']
             mem_free_torch = mem_reserved - mem_active
-            mem_free_total = torch.xpu.get_device_properties(dev).total_memory - mem_allocated
+            mem_free_xpu = torch.xpu.get_device_properties(dev).total_memory - mem_reserved
+            mem_free_total = mem_free_xpu + mem_free_torch
         else:
             stats = torch.cuda.memory_stats(dev)
             mem_active = stats['active_bytes.all.current']