support filling partial rows from backend (#4158)

Summary:

X-link: facebookresearch/FBGEMM#1238

change set
1. After enabling optimizer offloading, when read optimizer out, we want to only read the tailing bytes out instead of the whole value field. This isn't supported in EmbeddingRocksdb before,  add it here.
2. Once we have the functionality above, we dont need to call .narrow() or .continuous() on the output tensor anymore, remove those
3. We don't need optimizer chunking anymore(Ideally we can just return PMT to the checkpoint and let it handle KVT the same way as for weights)
4. fix UT bugs for constructing kv zch ssd tbe

Differential Revision: D75048595

Author: duduyi2013

fbgemm_gpu/fbgemm_gpu/split_table_batched_embeddings_ops_common.py

@@ -58,8 +58,6 @@ class KVZCHParams(NamedTuple):
     bucket_sizes: List[int] = []
     # enable optimizer offloading or not
     enable_optimizer_offloading: bool = False
-    # streaming load/save checkpoint chunk size
-    streaming_ckpt_chunk_size: int = 1000000
 
     def validate(self) -> None:
         assert len(self.bucket_offsets) == len(self.bucket_sizes), (

fbgemm_gpu/fbgemm_gpu/tbe/ssd/training.py

@@ -896,6 +896,8 @@ def _insert_all_kv(self) -> None:
             total_dim0 += dim0
 
         start_ts = time.time()
+        # TODO: do we have case for non-kvzch ssd with bulk init enabled + optimizer offloading? probably not?
+        #       if we have such cases, we should only init the emb dim not the optimizer dim
         chunk_tensor = torch.empty(
             row_count,
             self.cache_row_dim,
@@ -1944,9 +1946,8 @@ def split_optimizer_states(
 
         dtype = self.weights_precision.as_dtype()
         optimizer_dim = self.optimizer.state_size_dim(dtype)
-        pad4_optimizer_dim = pad4(optimizer_dim)
         logging.info(
-            f"split_optimizer_states: {optimizer_dim=} {pad4_optimizer_dim=} {self.optimizer.dtype()=} {self.enable_load_state_dict_mode=}"
+            f"split_optimizer_states: {optimizer_dim=}, {self.optimizer.dtype()=} {self.enable_load_state_dict_mode=}"
         )
 
         for t, (emb_height, emb_dim) in enumerate(self.embedding_specs):
@@ -1972,7 +1973,7 @@ def split_optimizer_states(
                         self.momentum1_dev.detach().cpu()[local_id_tensor].view(-1),
                     )
                 else:
-                    emb_opt_dim = pad4(emb_dim) + pad4_optimizer_dim
+                    emb_opt_dim = pad4(emb_dim) + optimizer_dim
                     row_offset = table_offset - (bucket_id_start * bucket_size)
                     # using KVTensorWrapper to query backend to avoid OOM memory, since
                     # backend will return both weight and optimizer in one tensor, read the whole tensor
@@ -1984,54 +1985,28 @@ def split_optimizer_states(
                         snapshot_handle=snapshot_handle,
                         materialized_shape=([sorted_id_tensor[t].size(0), emb_opt_dim]),
                         sorted_indices=sorted_id_tensor[t],
+                        width_offset=pad4(emb_dim),
                     )
                     (
                         tensor_wrapper.set_embedding_rocks_dp_wrapper(self.ssd_db)
                         if self.backend_type == BackendType.SSD
                         else tensor_wrapper.set_dram_db_wrapper(self.ssd_db)
                     )
                     opt_list.append(
-                        self.get_offloaded_optimizer_states(
-                            tensor_wrapper=tensor_wrapper,
-                            row=sorted_id_tensor[t].size(
-                                0
-                            ),  # we only need to copy the size of sorted_id_tensor
-                            optimizer_dim=optimizer_dim,
-                            start_dim_pos=pad4(emb_dim),
+                        tensor_wrapper.narrow(
+                            0,
+                            0,
+                            sorted_id_tensor[t].size(0),
                         )
+                        .view(-1)
+                        .view(self.optimizer.dtype())
                     )
             table_offset += emb_height
         logging.info(
             f"KV ZCH tables split_optimizer_states query latency: {(time.time() - start_time) * 1000} ms"
         )
         return opt_list
 
-    @torch.jit.export
-    def get_offloaded_optimizer_states(
-        self,
-        # pyre-ignore [2]
-        tensor_wrapper,
-        row: int,
-        optimizer_dim: int,
-        start_dim_pos: int,
-    ) -> torch.Tensor:
-        weight_dtype = self.weights_precision.as_dtype()
-        opt_state_t = torch.empty(
-            row, optimizer_dim, dtype=weight_dtype, device="cpu"
-        )  # 1D optimizer for OptimType.EXACT_ROWWISE_ADAGRAD
-
-        # pyre-ignore [16]
-        chunk_size = self.kv_zch_params.streaming_ckpt_chunk_size
-        for i in range(0, row, chunk_size):
-            length = min(chunk_size, row - i)
-            opt_state_t.narrow(0, i, length).copy_(
-                tensor_wrapper.narrow(0, i, length).narrow(
-                    1, start_dim_pos, optimizer_dim
-                )
-            )
-        # view optimizer state back to correct dtype
-        return opt_state_t.view(-1).view(self.optimizer.dtype())
-
     @torch.jit.export
     def get_optimizer_state(
         self,
@@ -2207,7 +2182,7 @@ def split_embedding_weights(
                         if bucket_ascending_id_tensor is not None
                         else emb_height
                     ),
-                    emb_dim,
+                    pad4(emb_dim),
                 ],
                 dtype=dtype,
                 row_offset=table_offset,

fbgemm_gpu/src/ssd_split_embeddings_cache/kv_db_table_batched_embeddings.cpp

@@ -457,7 +457,7 @@ void EmbeddingKVDB::set(
         << "]skip set_cuda since number evictions is " << num_evictions;
     return;
   }
-
+  CHECK_EQ(max_D_, weights.size(1));
   // defer the L2 cache/rocksdb update to the background thread as it could
   // be parallelized with other cuda kernels, as long as all updates are
   // finished before the next L2 cache lookup

fbgemm_gpu/src/ssd_split_embeddings_cache/kv_db_table_batched_embeddings.h

@@ -271,11 +271,15 @@ class EmbeddingKVDB : public std::enable_shared_from_this<EmbeddingKVDB> {
       const at::Tensor& weights,
       const int64_t start,
       const int64_t length,
-      const ssd::SnapshotHandle* snapshot_handle) {
+      const ssd::SnapshotHandle* snapshot_handle,
+      int64_t width_offset = 0,
+      std::optional<int64_t> width_length = std::nullopt) {
     (void)weights;
     (void)start;
     (void)length;
     (void)snapshot_handle;
+    (void)width_offset;
+    (void)width_length;
     FBEXCEPTION("Not implemented");
   }
 
@@ -287,10 +291,14 @@ class EmbeddingKVDB : public std::enable_shared_from_this<EmbeddingKVDB> {
   virtual void get_kv_from_storage_by_snapshot(
       const at::Tensor& ids,
       const at::Tensor& weights,
-      const ssd::SnapshotHandle* snapshot_handle) {
+      const ssd::SnapshotHandle* snapshot_handle,
+      int64_t width_offset = 0,
+      std::optional<int64_t> width_length = std::nullopt) {
     (void)ids;
     (void)weights;
     (void)snapshot_handle;
+    (void)width_offset;
+    (void)width_length;
     FBEXCEPTION("Not implemented");
   }
 

fbgemm_gpu/src/ssd_split_embeddings_cache/kv_tensor_wrapper.h

@@ -45,7 +45,8 @@ class KVTensorWrapper : public torch::jit::CustomClassHolder {
       int64_t row_offset,
       std::optional<c10::intrusive_ptr<EmbeddingSnapshotHandleWrapper>>
           snapshot_handle = std::nullopt,
-      std::optional<at::Tensor> sorted_indices = std::nullopt);
+      std::optional<at::Tensor> sorted_indices = std::nullopt,
+      int64_t width_offset = 0);
 
   at::Tensor narrow(int64_t dim, int64_t start, int64_t length);
 
@@ -97,6 +98,7 @@ class KVTensorWrapper : public torch::jit::CustomClassHolder {
   std::vector<int64_t> strides_;
   int64_t row_offset_;
   std::optional<at::Tensor> sorted_indices_ = std::nullopt;
+  int64_t width_offset_;
 };
 
 } // namespace ssd

fbgemm_gpu/src/ssd_split_embeddings_cache/kv_tensor_wrapper_cpu.cpp

@@ -34,7 +34,8 @@ KVTensorWrapper::KVTensorWrapper(
     int64_t row_offset,
     [[maybe_unused]] const std::optional<
         c10::intrusive_ptr<EmbeddingSnapshotHandleWrapper>> snapshot_handle,
-    [[maybe_unused]] const std::optional<at::Tensor> sorted_indices)
+    [[maybe_unused]] const std::optional<at::Tensor> sorted_indices,
+    [[maybe_unused]] int64_t width_offset)
     // @lint-ignore CLANGTIDY clang-diagnostic-missing-noreturn
     : shape_(std::move(shape)), row_offset_(row_offset) {
   FBEXCEPTION("Not implemented");

fbgemm_gpu/src/ssd_split_embeddings_cache/ssd_split_table_batched_embeddings.cpp

@@ -308,8 +308,13 @@ KVTensorWrapper::KVTensorWrapper(
     int64_t row_offset,
     const std::optional<c10::intrusive_ptr<EmbeddingSnapshotHandleWrapper>>
         snapshot_handle,
-    std::optional<at::Tensor> sorted_indices)
-    : db_(nullptr), shape_(std::move(shape)), row_offset_(row_offset) {
+    std::optional<at::Tensor> sorted_indices,
+    int64_t width_offset_)
+    : db_(nullptr),
+      shape_(std::move(shape)),
+      row_offset_(row_offset),
+      width_offset_(width_offset_) {
+  CHECK_GE(width_offset_, 0);
   CHECK_EQ(shape_.size(), 2) << "Only 2D emb tensors are supported";
   options_ = at::TensorOptions()
                  .dtype(static_cast<c10::ScalarType>(dtype))
@@ -342,25 +347,28 @@ void KVTensorWrapper::set_dram_db_wrapper(
 
 at::Tensor KVTensorWrapper::narrow(int64_t dim, int64_t start, int64_t length) {
   CHECK_EQ(dim, 0) << "Only narrow on dim 0 is supported";
-  CHECK_GE(db_->get_max_D(), shape_[1]);
   CHECK_TRUE(db_ != nullptr);
-  // Do not force snapshot handle is not nullptr since DRAM DB does not have
-  // rocksdb snapshot
+  CHECK_GE(db_->get_max_D(), shape_[1]);
+  TORCH_CHECK(
+      (snapshot_handle_ == nullptr) ==
+          (std::dynamic_pointer_cast<EmbeddingRocksDB>(db_).get() == nullptr),
+      "snapshot handler must be valid for rocksdb and nullptr for emb kvdb");
   if (!sorted_indices_.has_value()) {
-    auto t = at::empty(c10::IntArrayRef({length, db_->get_max_D()}), options_);
+    int64_t tensor_width = shape_[1] - width_offset_;
+    auto t = at::empty(c10::IntArrayRef({length, tensor_width}), options_);
     db_->get_range_from_snapshot(
         t,
         start + row_offset_,
         length,
-        snapshot_handle_ != nullptr ? snapshot_handle_->handle : nullptr);
-    // TBE may have multiple embeddings in one table padded to max D
-    // narrow to the actual shape here before returning
-    return t.narrow(1, 0, shape_[1]).contiguous();
+        snapshot_handle_ != nullptr ? snapshot_handle_->handle : nullptr,
+        width_offset_,
+        tensor_width);
+    CHECK(t.is_contiguous());
+    return t;
   } else {
     at::Tensor sliced_ids =
         sorted_indices_.value().slice(0, start, start + length);
-    auto out_weights = get_weights_by_ids(sliced_ids);
-    return out_weights.narrow(1, 0, shape_[1]).contiguous();
+    return get_weights_by_ids(sliced_ids);
   }
 }
 
@@ -404,14 +412,23 @@ void KVTensorWrapper::set_weights_and_ids(
 
 at::Tensor KVTensorWrapper::get_weights_by_ids(const at::Tensor& ids) {
   CHECK_TRUE(db_ != nullptr);
+  CHECK_GE(db_->get_max_D(), shape_[1]);
+  TORCH_CHECK(
+      (snapshot_handle_ == nullptr) ==
+          (std::dynamic_pointer_cast<EmbeddingRocksDB>(db_).get() == nullptr),
+      "snapshot handler must be valid for rocksdb and nullptr for emb kvdb");
+  int64_t tensor_width = shape_[1] - width_offset_;
   auto weights =
-      at::empty(c10::IntArrayRef({ids.size(0), db_->get_max_D()}), options_);
+      at::empty(c10::IntArrayRef({ids.size(0), tensor_width}), options_);
   auto linearized_ids = ids + row_offset_;
   db_->get_kv_from_storage_by_snapshot(
       linearized_ids,
       weights,
-      snapshot_handle_ != nullptr ? snapshot_handle_->handle : nullptr);
-  return weights.narrow(1, 0, shape_[1]);
+      snapshot_handle_ != nullptr ? snapshot_handle_->handle : nullptr,
+      width_offset_,
+      tensor_width);
+  CHECK(weights.is_contiguous());
+  return weights;
 }
 
 c10::IntArrayRef KVTensorWrapper::sizes() {
@@ -634,15 +651,17 @@ static auto kv_tensor_wrapper =
                 int64_t,
                 std::optional<
                     c10::intrusive_ptr<EmbeddingSnapshotHandleWrapper>>,
-                std::optional<at::Tensor>>(),
+                std::optional<at::Tensor>,
+                int64_t>(),
             "",
             {torch::arg("shape"),
              torch::arg("dtype"),
              torch::arg("row_offset"),
              // snapshot must be provided for reading
              // not needed for writing
              torch::arg("snapshot_handle") = std::nullopt,
-             torch::arg("sorted_indices") = std::nullopt})
+             torch::arg("sorted_indices") = std::nullopt,
+             torch::arg("width_offset") = 0})
         .def(
             "set_embedding_rocks_dp_wrapper",
             &KVTensorWrapper::set_embedding_rocks_dp_wrapper,