1 /* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
2 
3 Licensed under the Apache License, Version 2.0 (the "License");
4 you may not use this file except in compliance with the License.
5 You may obtain a copy of the License at
6 
7     http://www.apache.org/licenses/LICENSE-2.0
8 
9 Unless required by applicable law or agreed to in writing, software
10 distributed under the License is distributed on an "AS IS" BASIS,
11 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 See the License for the specific language governing permissions and
13 limitations under the License.
14 ==============================================================================*/
15 #ifndef TENSORFLOW_CORE_COMMON_RUNTIME_BUF_RENDEZVOUS_H_
16 #define TENSORFLOW_CORE_COMMON_RUNTIME_BUF_RENDEZVOUS_H_
17 
18 #include <functional>
19 #include <string>
20 
21 #include "absl/container/flat_hash_map.h"
22 #include "absl/strings/string_view.h"
23 #include "tensorflow/core/framework/allocator.h"
24 #include "tensorflow/core/framework/cancellation.h"
25 #include "tensorflow/core/lib/core/status.h"
26 #include "tensorflow/core/platform/mutex.h"
27 
28 namespace tensorflow {
29 class Device;
30 class DeviceContext;
31 class DeviceMgr;
32 class Tensor;
33 
34 // EXPERIMENTAL: RDMA oriented producer/consumer rendezvous on a local
35 // Tensor value for which DMAHelper::CanUseDMA() is true, i.e. dense
36 // numeric types.  Similar to Rendezvous but never owns a Ref on the
37 // tensor, instead it uses an explicit callback to the producer when
38 // the consumer side is finished with the value.  This allows the
39 // producer to perform in-place updates on the source buffer or to take
40 // other actions that depend on knowing the consumer has passed a certain
41 // execution point.
42 class BufRendezvous {
43  public:
BufRendezvous(uint64 step_id,const DeviceMgr * dev_mgr)44   explicit BufRendezvous(uint64 step_id, const DeviceMgr* dev_mgr)
45       : step_id_(step_id), dev_mgr_(dev_mgr) {}
46 
47   ~BufRendezvous();
48 
49   // Inform all waiting parties that this BufRendezvous is defunct because of
50   // an error Status interrupting the Step.
51   void StartAbort(const Status& s);
52 
53   struct Hook;
54   // Provided by the consumer to be called when access to the buffer
55   // is available.  If the Status arg is not OK, then hook will not
56   // be populated.  Ownership of Hook passes to consumer with the
57   // callback.
58   typedef std::function<void(const Status&, Hook*)> ConsumerCallback;
59   // Provided by the producer to be called when the consumer has finished
60   // reading the buffer and will no longer access it.
61   typedef std::function<void(const Status&)> ProducerCallback;
62 
63   struct Hook {
64     Device* prod_dev;
65     DeviceContext* prod_ctx;
66     const Tensor* prod_value;
67     AllocatorAttributes prod_attr;
68     ProducerCallback prod_cb;
69     ConsumerCallback cons_cb;
70     CancellationManager* cancellation_manager;
71     CancellationToken cancellation_token;
HookHook72     explicit Hook(CancellationManager* cancellation_manager,
73                   CancellationToken cancellation_token)
74         : prod_dev(nullptr),
75           prod_ctx(nullptr),
76           prod_value(nullptr),
77           prod_cb(nullptr),
78           cons_cb(nullptr),
79           cancellation_manager(cancellation_manager),
80           cancellation_token(cancellation_token) {}
81     string DebugString() const;
82   };
83 
84   // Called to advertise availability of a Tensor value corresponding
85   // to key.  That value must stay valid until done is called.
86   //
87   // If a non-null cancellation manager is provided, this function registers a
88   // callback to delete the hook and invoke provider/consumer callbacks with
89   // cancelled error.
90   void ProvideBuf(const string& key, Device* dev, DeviceContext* dev_ctx,
91                   const Tensor* v, const AllocatorAttributes& attr,
92                   const ProducerCallback& done,
93                   CancellationManager* cancellation_manager);
94 
95   // Called to request access to a Tensor value corresponding to key.
96   // Consumer is provided with a Hook as soon as available.
97   //
98   // This function also checks that the current incarnation number of the
99   // `device` that produced this value matches the `incarnation` expected by the
100   // consumer, and invokes `done` with `FailedPrecondition` status and
101   // `nullptr` hook if it does not match.
102   //
103   // If a non-null cancellation manager is provided, this function registers a
104   // callback to delete the hook and invoke provider/consumer callbacks with
105   // cancelled error.
106   void ConsumeBuf(const string& key, const string& device,
107                   const uint64 incarnation, const ConsumerCallback& done,
108                   CancellationManager* cancellation_manager);
109 
110   // Cancel the rendezvous entry corresponding to `key`.  Triggered by the
111   // cancellation manager. No-op if the rendezvous was already successful.
112   void CancelHook(const string& key);
113 
114   // Consumer must call this function when it's done reading the Hook provided
115   // by the ConsumerCallback.  This function will invoke the producer callback
116   // and then delete h.
117   static void DoneWithHook(Hook* h);
118 
119   // Write the current contents of the table to the INFO log.
120   void LogContents();
121 
122  protected:
123   const uint64 step_id_;
124   const DeviceMgr* const dev_mgr_;  // Not owned.
125   mutex mu_;
126   Status status_ TF_GUARDED_BY(mu_);
127   typedef absl::flat_hash_map<string, Hook*> HookTable;
128   HookTable hook_table_ TF_GUARDED_BY(mu_);
129 
130   void PurgeTable(const Status& s, HookTable* table);
131 };
132 }  // namespace tensorflow
133 #endif  // TENSORFLOW_CORE_COMMON_RUNTIME_BUF_RENDEZVOUS_H_
134