Try to fix OOM issues with cards that have less vram than mine.

comfy/ldm/modules/attention.py

@@ -194,7 +194,14 @@ class CrossAttentionBirchSan(nn.Module):
 
         kv_chunk_size_min = None
 
-        query_chunk_size_x = 1024 * 4
+        #not sure at all about the math here
+        #TODO: tweak this
+        if mem_free_total > 8192 * 1024 * 1024 * 1.3:
+            query_chunk_size_x = 1024 * 4
+        elif mem_free_total > 4096 * 1024 * 1024 * 1.3:
+            query_chunk_size_x = 1024 * 2
+        else:
+            query_chunk_size_x = 1024
         kv_chunk_size_min_x = None
         kv_chunk_size_x = (int((chunk_threshold_bytes // (batch_x_heads * bytes_per_token * query_chunk_size_x)) * 2.0) // 1024) * 1024
         if kv_chunk_size_x < 1024: