CPU Pinned embedding Layer (intel#9538)

* CPU Pinned embedding

python/llm/src/bigdl/llm/transformers/embedding.py

@@ -17,11 +17,40 @@
 
 import torch
 from torch import Tensor
+from torch.nn import functional as F
+from torch.nn import Parameter
+from typing import Optional
+
+
+# To prevent insufficient available memory when moving embedding from XPU back to CPU,
+# we can pin the embedding to CPU if `cpu_embedding==True`.
+class CPUPinnedParam(Parameter):
+    def to(self, *args, **kwargs):
+        device, dtype, non_blocking, convert_to_format = torch._C._nn._parse_to(*args, **kwargs)
+        if device.type == 'xpu':
+            if convert_to_format is not None and self.dim() in (4, 5):
+                return super().to('cpu', dtype,
+                                  non_blocking, memory_format=convert_to_format)
+            return super().to('cpu', dtype, non_blocking)
+        return super().to(*args, **kwargs)
 
 
 class LLMEmbedding(torch.nn.Embedding):
+    def __init__(self,
+                 num_embeddings: int,
+                 embedding_dim: int,
+                 padding_idx: Optional[int] = None,
+                 max_norm: Optional[float] = None,
+                 norm_type: float = 2.,
+                 scale_grad_by_freq: bool = False,
+                 sparse: bool = False,
+                 _weight: Optional[Tensor] = None,
+                 _freeze: bool = False,
+                 device=None, dtype=None) -> None:
+        super().__init__(num_embeddings, embedding_dim, padding_idx,
+                         max_norm, norm_type, scale_grad_by_freq, sparse,
+                         _weight, device, dtype)
+        self.weight = CPUPinnedParam(self.weight.data, requires_grad=not _freeze)
+
     def forward(self, x: Tensor):
-        if self.weight.device != 'cpu':
-            self.to('cpu')
-            torch.xpu.empty_cache()
         return super().forward(x.to('cpu')).to(x.device)