Export of internal Abseil changes

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3794fe8db7a8e5a17945a8d6e198cde1db1fed7d by Chris Kennelly <[email protected]>:

Record maximum reserve or rehash argument in hashtable statistics.

This makes it possible to identify containers that are large because of reserve
calls or ones that could have an opportunity for more precise capacity sizing.

PiperOrigin-RevId: 396851064

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c3d247c08acfd45d8e19cfd8e6e841e16e38e23d by Abseil Team <[email protected]>:

Remove extra semi-colon

PiperOrigin-RevId: 396823800
GitOrigin-RevId: 3794fe8db7a8e5a17945a8d6e198cde1db1fed7d
Change-Id: I9f26407c2dc6b3dff04f6f3e249571dd8ab288c3

Author: Abseil Team

absl/container/internal/hashtablez_sampler.cc

@@ -68,6 +68,7 @@ void HashtablezInfo::PrepareForSampling() {
   hashes_bitwise_or.store(0, std::memory_order_relaxed);
   hashes_bitwise_and.store(~size_t{}, std::memory_order_relaxed);
   hashes_bitwise_xor.store(0, std::memory_order_relaxed);
+  max_reserve.store(0, std::memory_order_relaxed);
 
   create_time = absl::Now();
   // The inliner makes hardcoded skip_count difficult (especially when combined

absl/container/internal/hashtablez_sampler.h

@@ -80,6 +80,7 @@ struct HashtablezInfo : public profiling_internal::Sample<HashtablezInfo> {
   std::atomic<size_t> hashes_bitwise_or;
   std::atomic<size_t> hashes_bitwise_and;
   std::atomic<size_t> hashes_bitwise_xor;
+  std::atomic<size_t> max_reserve;
 
   // All of the fields below are set by `PrepareForSampling`, they must not be
   // mutated in `Record*` functions.  They are logically `const` in that sense.
@@ -107,6 +108,18 @@ inline void RecordRehashSlow(HashtablezInfo* info, size_t total_probe_length) {
       std::memory_order_relaxed);
 }
 
+inline void RecordReservationSlow(HashtablezInfo* info,
+                                  size_t target_capacity) {
+  info->max_reserve.store(
+      (std::max)(info->max_reserve.load(std::memory_order_relaxed),
+                 target_capacity),
+      std::memory_order_relaxed);
+}
+
+inline void RecordClearedReservationSlow(HashtablezInfo* info) {
+  info->max_reserve.store(0, std::memory_order_relaxed);
+}
+
 inline void RecordStorageChangedSlow(HashtablezInfo* info, size_t size,
                                      size_t capacity) {
   info->size.store(size, std::memory_order_relaxed);
@@ -170,6 +183,16 @@ class HashtablezInfoHandle {
     RecordRehashSlow(info_, total_probe_length);
   }
 
+  inline void RecordReservation(size_t target_capacity) {
+    if (ABSL_PREDICT_TRUE(info_ == nullptr)) return;
+    RecordReservationSlow(info_, target_capacity);
+  }
+
+  inline void RecordClearedReservation() {
+    if (ABSL_PREDICT_TRUE(info_ == nullptr)) return;
+    RecordClearedReservationSlow(info_);
+  }
+
   inline void RecordInsert(size_t hash, size_t distance_from_desired) {
     if (ABSL_PREDICT_TRUE(info_ == nullptr)) return;
     RecordInsertSlow(info_, hash, distance_from_desired);
@@ -199,6 +222,8 @@ class HashtablezInfoHandle {
 
   inline void RecordStorageChanged(size_t /*size*/, size_t /*capacity*/) {}
   inline void RecordRehash(size_t /*total_probe_length*/) {}
+  inline void RecordReservation(size_t /*target_capacity*/) {}
+  inline void RecordClearedReservation() {}
   inline void RecordInsert(size_t /*hash*/, size_t /*distance_from_desired*/) {}
   inline void RecordErase() {}
 

absl/container/internal/hashtablez_sampler_test.cc

@@ -91,6 +91,7 @@ TEST(HashtablezInfoTest, PrepareForSampling) {
   EXPECT_EQ(info.hashes_bitwise_or.load(), 0);
   EXPECT_EQ(info.hashes_bitwise_and.load(), ~size_t{});
   EXPECT_EQ(info.hashes_bitwise_xor.load(), 0);
+  EXPECT_EQ(info.max_reserve.load(), 0);
   EXPECT_GE(info.create_time, test_start);
 
   info.capacity.store(1, std::memory_order_relaxed);
@@ -101,6 +102,7 @@ TEST(HashtablezInfoTest, PrepareForSampling) {
   info.hashes_bitwise_or.store(1, std::memory_order_relaxed);
   info.hashes_bitwise_and.store(1, std::memory_order_relaxed);
   info.hashes_bitwise_xor.store(1, std::memory_order_relaxed);
+  info.max_reserve.store(1, std::memory_order_relaxed);
   info.create_time = test_start - absl::Hours(20);
 
   info.PrepareForSampling();
@@ -113,6 +115,7 @@ TEST(HashtablezInfoTest, PrepareForSampling) {
   EXPECT_EQ(info.hashes_bitwise_or.load(), 0);
   EXPECT_EQ(info.hashes_bitwise_and.load(), ~size_t{});
   EXPECT_EQ(info.hashes_bitwise_xor.load(), 0);
+  EXPECT_EQ(info.max_reserve.load(), 0);
   EXPECT_GE(info.create_time, test_start);
 }
 
@@ -187,6 +190,22 @@ TEST(HashtablezInfoTest, RecordRehash) {
   EXPECT_EQ(info.num_rehashes.load(), 1);
 }
 
+TEST(HashtablezInfoTest, RecordReservation) {
+  HashtablezInfo info;
+  absl::MutexLock l(&info.init_mu);
+  info.PrepareForSampling();
+  RecordReservationSlow(&info, 3);
+  EXPECT_EQ(info.max_reserve.load(), 3);
+
+  RecordReservationSlow(&info, 2);
+  // High watermark does not change
+  EXPECT_EQ(info.max_reserve.load(), 3);
+
+  RecordReservationSlow(&info, 10);
+  // High watermark does change
+  EXPECT_EQ(info.max_reserve.load(), 10);
+}
+
 #if defined(ABSL_INTERNAL_HASHTABLEZ_SAMPLE)
 TEST(HashtablezSamplerTest, SmallSampleParameter) {
   SetHashtablezEnabled(true);

absl/container/internal/raw_hash_set.h

@@ -1069,6 +1069,8 @@ class raw_hash_set {
     // past that we simply deallocate the array.
     if (capacity_ > 127) {
       destroy_slots();
+
+      infoz().RecordClearedReservation();
     } else if (capacity_) {
       for (size_t i = 0; i != capacity_; ++i) {
         if (IsFull(ctrl_[i])) {
@@ -1382,21 +1384,31 @@ class raw_hash_set {
     if (n == 0 && size_ == 0) {
       destroy_slots();
       infoz().RecordStorageChanged(0, 0);
+      infoz().RecordClearedReservation();
       return;
     }
+
     // bitor is a faster way of doing `max` here. We will round up to the next
     // power-of-2-minus-1, so bitor is good enough.
     auto m = NormalizeCapacity(n | GrowthToLowerboundCapacity(size()));
     // n == 0 unconditionally rehashes as per the standard.
     if (n == 0 || m > capacity_) {
       resize(m);
+
+      // This is after resize, to ensure that we have completed the allocation
+      // and have potentially sampled the hashtable.
+      infoz().RecordReservation(n);
     }
   }
 
   void reserve(size_t n) {
     if (n > size() + growth_left()) {
       size_t m = GrowthToLowerboundCapacity(n);
       resize(NormalizeCapacity(m));
+
+      // This is after resize, to ensure that we have completed the allocation
+      // and have potentially sampled the hashtable.
+      infoz().RecordReservation(n);
     }
   }
 
@@ -1638,6 +1650,7 @@ class raw_hash_set {
         PolicyTraits::destroy(&alloc_ref(), slots_ + i);
       }
     }
+
     // Unpoison before returning the memory to the allocator.
     SanitizerUnpoisonMemoryRegion(slots_, sizeof(slot_type) * capacity_);
     Deallocate<alignof(slot_type)>(

absl/container/internal/raw_hash_set_test.cc

@@ -2049,15 +2049,31 @@ TEST(RawHashSamplerTest, Sample) {
   std::vector<IntTable> tables;
   for (int i = 0; i < 1000000; ++i) {
     tables.emplace_back();
+
+    const bool do_reserve = (i % 10 > 5);
+    const bool do_rehash = !do_reserve && (i % 10 > 0);
+
+    if (do_reserve) {
+      // Don't reserve on all tables.
+      tables.back().reserve(10 * (i % 10));
+    }
+
     tables.back().insert(1);
     tables.back().insert(i % 5);
+
+    if (do_rehash) {
+      // Rehash some other tables.
+      tables.back().rehash(10 * (i % 10));
+    }
   }
   size_t end_size = 0;
   std::unordered_map<size_t, int> observed_checksums;
+  std::unordered_map<ssize_t, int> reservations;
   end_size += sampler.Iterate([&](const HashtablezInfo& info) {
     if (preexisting_info.count(&info) == 0) {
       observed_checksums[info.hashes_bitwise_xor.load(
           std::memory_order_relaxed)]++;
+      reservations[info.max_reserve.load(std::memory_order_relaxed)]++;
     }
     ++end_size;
   });
@@ -2068,6 +2084,15 @@ TEST(RawHashSamplerTest, Sample) {
   for (const auto& [_, count] : observed_checksums) {
     EXPECT_NEAR((100 * count) / static_cast<double>(tables.size()), 0.2, 0.05);
   }
+
+  EXPECT_EQ(reservations.size(), 10);
+  for (const auto& [reservation, count] : reservations) {
+    EXPECT_GE(reservation, 0);
+    EXPECT_LT(reservation, 100);
+
+    EXPECT_NEAR((100 * count) / static_cast<double>(tables.size()), 0.1, 0.05)
+        << reservation;
+  }
 }
 #endif  // ABSL_INTERNAL_HASHTABLEZ_SAMPLE
 

absl/strings/internal/cord_rep_btree_reader.h

@@ -166,7 +166,7 @@ inline size_t CordRepBtreeReader::length() const {
 inline absl::string_view CordRepBtreeReader::Init(CordRepBtree* tree) {
   assert(tree != nullptr);
   const CordRep* edge = navigator_.InitFirst(tree);
-  remaining_ = tree->length - edge->length;;
+  remaining_ = tree->length - edge->length;
   return CordRepBtree::EdgeData(edge);
 }