Exllama cache 8bit (#2719)

lm-sys · Nov 23, 2023 · 6ac7d76 · 6ac7d76
1 parent ff25295
commit 6ac7d76
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diff --git a/docs/exllama_v2.md b/docs/exllama_v2.md
@@ -41,6 +41,8 @@ python3 -m fastchat.serve.model_worker \
     --exllama-gpu-split 18,24
 ```
 
+`--exllama-cache-8bit` can be used to enable 8-bit caching with exllama and save some VRAM.
+
 ## Performance 
 
 Reference: https://github.com/turboderp/exllamav2#performance

diff --git a/fastchat/model/model_adapter.py b/fastchat/model/model_adapter.py
@@ -501,6 +501,11 @@ def add_model_args(parser):
         default=None,
         help="Used for exllamabv2. Comma-separated list of VRAM (in GB) to use per GPU. Example: 20,7,7",
     )
+    parser.add_argument(
+        "--exllama-cache-8bit",
+        action="store_true",
+        help="Used for exllamabv2. Use 8-bit cache to save VRAM.",
+    )
     parser.add_argument(
         "--enable-xft",
         action="store_true",

diff --git a/fastchat/modules/exllama.py b/fastchat/modules/exllama.py
@@ -6,6 +6,7 @@
 class ExllamaConfig:
     max_seq_len: int
     gpu_split: str = None
+    cache_8bit: bool = False
 
 
 class ExllamaModel:
@@ -22,6 +23,7 @@ def load_exllama_model(model_path, exllama_config: ExllamaConfig):
             ExLlamaV2Tokenizer,
             ExLlamaV2,
             ExLlamaV2Cache,
+            ExLlamaV2Cache_8bit,
         )
     except ImportError as e:
         print(f"Error: Failed to load Exllamav2. {e}")
@@ -31,6 +33,7 @@ def load_exllama_model(model_path, exllama_config: ExllamaConfig):
     exllamav2_config.model_dir = model_path
     exllamav2_config.prepare()
     exllamav2_config.max_seq_len = exllama_config.max_seq_len
+    exllamav2_config.cache_8bit = exllama_config.cache_8bit
 
     exllama_model = ExLlamaV2(exllamav2_config)
     tokenizer = ExLlamaV2Tokenizer(exllamav2_config)
@@ -40,7 +43,8 @@ def load_exllama_model(model_path, exllama_config: ExllamaConfig):
         split = [float(alloc) for alloc in exllama_config.gpu_split.split(",")]
     exllama_model.load(split)
 
-    exllama_cache = ExLlamaV2Cache(exllama_model)
+    cache_class = ExLlamaV2Cache_8bit if exllamav2_config.cache_8bit else ExLlamaV2Cache
+    exllama_cache = cache_class(exllama_model)
     model = ExllamaModel(exllama_model=exllama_model, exllama_cache=exllama_cache)
 
     return model, tokenizer
diff --git a/fastchat/serve/cli.py b/fastchat/serve/cli.py
@@ -201,6 +201,7 @@ def main(args):
         exllama_config = ExllamaConfig(
             max_seq_len=args.exllama_max_seq_len,
             gpu_split=args.exllama_gpu_split,
+            cache_8bit=args.exllama_cache_8bit,
         )
     else:
         exllama_config = None

diff --git a/fastchat/serve/model_worker.py b/fastchat/serve/model_worker.py
@@ -323,6 +323,7 @@ def create_model_worker():
         exllama_config = ExllamaConfig(
             max_seq_len=args.exllama_max_seq_len,
             gpu_split=args.exllama_gpu_split,
+            cache_8bit=args.exllama_cache_8bit,
         )
     else:
         exllama_config = None

diff --git a/fastchat/serve/multi_model_worker.py b/fastchat/serve/multi_model_worker.py
@@ -217,6 +217,7 @@ def create_multi_model_worker():
         exllama_config = ExllamaConfig(
             max_seq_len=args.exllama_max_seq_len,
             gpu_split=args.exllama_gpu_split,
+            cache_8bit=args.exllama_cache_8bit,
         )
     else:
         exllama_config = None