Disabling exllama on old compute. (#986)

# What does this PR do?

Disabling exllama on old compute.

Exllama + T4 don't play nice together, this will disable it right away
to avoid issues at runtime.

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Fixes # (issue)


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server/text_generation_server/utils/layers.py

@@ -18,13 +18,20 @@ from accelerate import init_empty_weights
 
 from text_generation_server.utils.gptq.quant_linear import QuantLinear
 
-HAS_EXLLAMA = True
+try:
+    major, _minor = torch.cuda.get_device_capability()
+except Exception:
+    major = 1
+HAS_EXLLAMA = False
+CAN_EXLLAMA = major >= 8
 if os.getenv("DISABLE_EXLLAMA") == "True":
     HAS_EXLLAMA = False
-try:
+elif CAN_EXLLAMA:
+        try:
             from text_generation_server.utils.gptq.exllama import Ex4bitLinear
-except ImportError:
+            HAS_EXLLAMA = True
-    HAS_EXLLAMA = False
+        except ImportError:
+            pass
 
 from typing import Optional
 

server/text_generation_server/utils/weights.py

@@ -170,10 +170,10 @@ class Weights:
                     "Cannot load `gptq` weight, make sure the model is already quantized, or quantize it with `text-generation-server quantize ORIGINAL_MODEL_ID NEW_MODEL_ID`"
                 )
 
-            from text_generation_server.utils.layers import HAS_EXLLAMA
+            from text_generation_server.utils.layers import HAS_EXLLAMA, CAN_EXLLAMA
 
             if use_exllama:
-                if not HAS_EXLLAMA:
+                if not HAS_EXLLAMA and CAN_EXLLAMA:
                     logger.warning(
                         "Exllama GPTQ cuda kernels (which are faster) could have been used, but are not currently installed, try using BUILD_EXTENSIONS=True"
                     )