[Mem Snapshot] Add Metadata Field (#165490)

Summary:
The implementation adds the ability to:

Set custom metadata strings that will be attached to all subsequent allocations
Clear or change the metadata at any point
View the metadata in memory snapshots via _dump_snapshot()

Test Plan: Added test in test_cuda.py and check manually in snapshot to see that metadata was added.

Differential Revision: D84654933

Pull Request resolved: https://github.com/pytorch/pytorch/pull/165490
Approved by: https://github.com/yushangdi

c10/cuda/CUDACachingAllocator.cpp

@@ -1260,6 +1260,9 @@ class DeviceCachingAllocator {
   // thread local compile context for each device
   static thread_local std::stack<std::string> compile_context;
 
+  // thread local user metadata for annotating allocations
+  static thread_local std::string user_metadata;
+
  public:
   // NOLINTNEXTLINE(cppcoreguidelines-pro-type-member-init)
   explicit DeviceCachingAllocator(c10::DeviceIndex id)
@@ -1302,6 +1305,14 @@ class DeviceCachingAllocator {
     }
   }
 
+  void setUserMetadata(const std::string& metadata) {
+    user_metadata = metadata;
+  }
+
+  std::string getUserMetadata() {
+    return user_metadata;
+  }
+
   bool checkPoolLiveAllocations(
       MempoolId_t mempool_id,
       const std::unordered_set<void*>& expected_live_allocations) const {
@@ -3682,7 +3693,8 @@ class DeviceCachingAllocator {
         mempool_id,
         getApproximateTime(),
         record_context_ >= RecordContext::ALLOC ? std::move(context) : nullptr,
-        compile_string);
+        compile_string,
+        user_metadata);
 
     // Callbacks should not include any Pytorch call
     for (const auto& cb : trace_trackers_) {
@@ -3737,6 +3749,7 @@ static void uncached_delete(void* ptr) {
 
 static void local_raw_delete(void* ptr);
 thread_local std::stack<std::string> DeviceCachingAllocator::compile_context;
+thread_local std::string DeviceCachingAllocator::user_metadata;
 #ifdef __cpp_lib_hardware_interference_size
 using std::hardware_destructive_interference_size;
 #else
@@ -3934,6 +3947,18 @@ class NativeCachingAllocator : public CUDAAllocator {
     device_allocator[device]->popCompileContext();
   }
 
+  void setUserMetadata(const std::string& metadata) override {
+    c10::DeviceIndex device = 0;
+    C10_CUDA_CHECK(c10::cuda::GetDevice(&device));
+    device_allocator[device]->setUserMetadata(metadata);
+  }
+
+  std::string getUserMetadata() override {
+    c10::DeviceIndex device = 0;
+    C10_CUDA_CHECK(c10::cuda::GetDevice(&device));
+    return device_allocator[device]->getUserMetadata();
+  }
+
   bool isHistoryEnabled() override {
     c10::DeviceIndex device = 0;
     C10_CUDA_CHECK(c10::cuda::GetDevice(&device));

c10/cuda/CUDACachingAllocator.h

@@ -118,7 +118,8 @@ struct TraceEntry {
       MempoolId_t mempool,
       approx_time_t time,
       std::shared_ptr<GatheredContext> context = nullptr,
-      std::string compile_context = "")
+      std::string compile_context = "",
+      std::string user_metadata = "")
       : action_(action),
         device_(device),
         addr_(addr),
@@ -126,7 +127,8 @@ struct TraceEntry {
         stream_(stream),
         size_(size),
         mempool_(std::move(mempool)),
-        compile_context_(std::move(compile_context)) {
+        compile_context_(std::move(compile_context)),
+        user_metadata_(std::move(user_metadata)) {
     time_.approx_t_ = time;
   }
   Action action_;
@@ -138,6 +140,7 @@ struct TraceEntry {
   MempoolId_t mempool_;
   trace_time_ time_{};
   std::string compile_context_;
+  std::string user_metadata_;
 };
 
 // Calls made by record_function will save annotations
@@ -297,6 +300,10 @@ class CUDAAllocator : public DeviceAllocator {
       const std::vector<std::pair<std::string, std::string>>& /*md*/) {}
   virtual void pushCompileContext(std::string& md) {}
   virtual void popCompileContext() {}
+  virtual void setUserMetadata(const std::string& metadata) {}
+  virtual std::string getUserMetadata() {
+    return "";
+  }
   virtual void attachOutOfMemoryObserver(OutOfMemoryObserver observer) = 0;
 
   // Attached AllocatorTraceTracker callbacks will be called while the
@@ -536,6 +543,14 @@ inline void enablePeerAccess(
   get()->enablePeerAccess(dev, dev_to_access);
 }
 
+inline void setUserMetadata(const std::string& metadata) {
+  get()->setUserMetadata(metadata);
+}
+
+inline std::string getUserMetadata() {
+  return get()->getUserMetadata();
+}
+
 } // namespace c10::cuda::CUDACachingAllocator
 
 namespace c10::cuda {