Prs/lora reservations (reduce massive Lora reservations especially on Flux2) (#11069)

* mp: only count the offload cost of math once

This was previously bundling the combined weight storage and computation
cost

* ops: put all post async transfer compute on the main stream

Some models have massive weights that need either complex
dequantization or lora patching. Don't do these patchings on the offload
stream, instead do them on the main stream to syncrhonize the
potentially large vram spikes for these compute processes. This avoids
having to assume a worst case scenario of multiple offload streams
all spiking VRAM is parallel with whatever the main stream is doing.

comfy/model_patcher.py

@@ -704,7 +704,7 @@ class ModelPatcher:
 
                 lowvram_weight = False
 
-                potential_offload = max(offload_buffer, module_offload_mem * (comfy.model_management.NUM_STREAMS + 1))
+                potential_offload = max(offload_buffer, module_offload_mem + (comfy.model_management.NUM_STREAMS * module_mem))
                 lowvram_fits = mem_counter + module_mem + potential_offload < lowvram_model_memory
 
                 weight_key = "{}.weight".format(n)
@@ -883,7 +883,7 @@ class ModelPatcher:
                     break
                 module_offload_mem, module_mem, n, m, params = unload
 
-                potential_offload = (comfy.model_management.NUM_STREAMS + 1) * module_offload_mem
+                potential_offload = module_offload_mem + (comfy.model_management.NUM_STREAMS * module_mem)
 
                 lowvram_possible = hasattr(m, "comfy_cast_weights")
                 if hasattr(m, "comfy_patched_weights") and m.comfy_patched_weights == True:

comfy/ops.py

@@ -111,22 +111,24 @@ def cast_bias_weight(s, input=None, dtype=None, device=None, bias_dtype=None, of
     if s.bias is not None:
         bias = comfy.model_management.cast_to(s.bias, bias_dtype, device, non_blocking=non_blocking, copy=bias_has_function, stream=offload_stream)
 
-        if bias_has_function:
+    comfy.model_management.sync_stream(device, offload_stream)
-            with wf_context:
+
+    bias_a = bias
+    weight_a = weight
+
+    if s.bias is not None:
         for f in s.bias_function:
             bias = f(bias)
 
     if weight_has_function or weight.dtype != dtype:
-        with wf_context:
         weight = weight.to(dtype=dtype)
         if isinstance(weight, QuantizedTensor):
             weight = weight.dequantize()
         for f in s.weight_function:
             weight = f(weight)
 
-    comfy.model_management.sync_stream(device, offload_stream)
     if offloadable:
-        return weight, bias, offload_stream
+        return weight, bias, (offload_stream, weight_a, bias_a)
     else:
         #Legacy function signature
         return weight, bias
@@ -135,13 +137,16 @@ def cast_bias_weight(s, input=None, dtype=None, device=None, bias_dtype=None, of
 def uncast_bias_weight(s, weight, bias, offload_stream):
     if offload_stream is None:
         return
-    if weight is not None:
+    os, weight_a, bias_a = offload_stream
-        device = weight.device
+    if os is None:
-    else:
-        if bias is None:
         return
-        device = bias.device
+    if weight_a is not None:
-    offload_stream.wait_stream(comfy.model_management.current_stream(device))
+        device = weight_a.device
+    else:
+        if bias_a is None:
+            return
+        device = bias_a.device
+    os.wait_stream(comfy.model_management.current_stream(device))
 
 
 class CastWeightBiasOp: