Export of internal Abseil changes

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ca3a0009e675b699b5d6dd41f00ebac0e7d1935c by Derek Mauro <dmauro@google.com>:

Internal change

PiperOrigin-RevId: 396475923

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04d9fff79085bb18612af3da49007907394ae0b6 by Abseil Team <absl-team@google.com>:

Move HastablezSampler from container/internal to profiling/internal.

PiperOrigin-RevId: 396362093
GitOrigin-RevId: ca3a0009e675b699b5d6dd41f00ebac0e7d1935c
Change-Id: I42d6d2944786afa24259fde002fed5e611f4e1f9

1 files changed, 6 insertions, 75 deletions

diff --git a/absl/container/internal/hashtablez_sampler.h b/absl/container/internal/hashtablez_sampler.h
index 85685f72..d86207f5 100644
--- a/absl/container/internal/hashtablez_sampler.h
+++ b/absl/container/internal/hashtablez_sampler.h
@@ -47,6 +47,7 @@
 #include "absl/base/internal/per_thread_tls.h"
 #include "absl/base/optimization.h"
 #include "absl/container/internal/have_sse.h"
+#include "absl/profiling/internal/sample_recorder.h"
 #include "absl/synchronization/mutex.h"
 #include "absl/utility/utility.h"
 
@@ -57,7 +58,7 @@ namespace container_internal {
 // Stores information about a sampled hashtable.  All mutations to this *must*
 // be made through `Record*` functions below.  All reads from this *must* only
 // occur in the callback to `HashtablezSampler::Iterate`.
-struct HashtablezInfo {
+struct HashtablezInfo : public profiling_internal::Sample<HashtablezInfo> {
   // Constructs the object but does not fill in any fields.
   HashtablezInfo();
   ~HashtablezInfo();
@@ -80,14 +81,6 @@ struct HashtablezInfo {
   std::atomic<size_t> hashes_bitwise_and;
   std::atomic<size_t> hashes_bitwise_xor;
 
-  // `HashtablezSampler` maintains intrusive linked lists for all samples.  See
-  // comments on `HashtablezSampler::all_` for details on these.  `init_mu`
-  // guards the ability to restore the sample to a pristine state.  This
-  // prevents races with sampling and resurrecting an object.
-  absl::Mutex init_mu;
-  HashtablezInfo* next;
-  HashtablezInfo* dead ABSL_GUARDED_BY(init_mu);
-
   // All of the fields below are set by `PrepareForSampling`, they must not be
   // mutated in `Record*` functions.  They are logically `const` in that sense.
   // These are guarded by init_mu, but that is not externalized to clients, who
@@ -231,73 +224,11 @@ inline HashtablezInfoHandle Sample() {
 #endif  // !ABSL_PER_THREAD_TLS
 }
 
-// Holds samples and their associated stack traces with a soft limit of
-// `SetHashtablezMaxSamples()`.
-//
-// Thread safe.
-class HashtablezSampler {
- public:
-  // Returns a global Sampler.
-  static HashtablezSampler& Global();
-
-  HashtablezSampler();
-  ~HashtablezSampler();
-
-  // Registers for sampling.  Returns an opaque registration info.
-  HashtablezInfo* Register();
+using HashtablezSampler =
+    ::absl::profiling_internal::SampleRecorder<HashtablezInfo>;
 
-  // Unregisters the sample.
-  void Unregister(HashtablezInfo* sample);
-
-  // The dispose callback will be called on all samples the moment they are
-  // being unregistered. Only affects samples that are unregistered after the
-  // callback has been set.
-  // Returns the previous callback.
-  using DisposeCallback = void (*)(const HashtablezInfo&);
-  DisposeCallback SetDisposeCallback(DisposeCallback f);
-
-  // Iterates over all the registered `StackInfo`s.  Returning the number of
-  // samples that have been dropped.
-  int64_t Iterate(const std::function<void(const HashtablezInfo& stack)>& f);
-
- private:
-  void PushNew(HashtablezInfo* sample);
-  void PushDead(HashtablezInfo* sample);
-  HashtablezInfo* PopDead();
-
-  std::atomic<size_t> dropped_samples_;
-  std::atomic<size_t> size_estimate_;
-
-  // Intrusive lock free linked lists for tracking samples.
-  //
-  // `all_` records all samples (they are never removed from this list) and is
-  // terminated with a `nullptr`.
-  //
-  // `graveyard_.dead` is a circular linked list.  When it is empty,
-  // `graveyard_.dead == &graveyard`.  The list is circular so that
-  // every item on it (even the last) has a non-null dead pointer.  This allows
-  // `Iterate` to determine if a given sample is live or dead using only
-  // information on the sample itself.
-  //
-  // For example, nodes [A, B, C, D, E] with [A, C, E] alive and [B, D] dead
-  // looks like this (G is the Graveyard):
-  //
-  //           +---+    +---+    +---+    +---+    +---+
-  //    all -->| A |--->| B |--->| C |--->| D |--->| E |
-  //           |   |    |   |    |   |    |   |    |   |
-  //   +---+   |   | +->|   |-+  |   | +->|   |-+  |   |
-  //   | G |   +---+ |  +---+ |  +---+ |  +---+ |  +---+
-  //   |   |         |        |        |        |
-  //   |   | --------+        +--------+        |
-  //   +---+                                    |
-  //     ^                                      |
-  //     +--------------------------------------+
-  //
-  std::atomic<HashtablezInfo*> all_;
-  HashtablezInfo graveyard_;
-
-  std::atomic<DisposeCallback> dispose_;
-};
+// Returns a global Sampler.
+HashtablezSampler& GlobalHashtablezSampler();
 
 // Enables or disables sampling for Swiss tables.
 void SetHashtablezEnabled(bool enabled);