[sampling profiler] replace samples std::set with unordered_map

unordered_map is supposedly faster on deleting items.

BUG=chromium:889545

Change-Id: Id92d9d663e8b9ab2978b8016ef5dccfc93dc104e
Reviewed-on: https://chromium-review.googlesource.com/1255554Reviewed-by: Ali Ijaz Sheikh <ofrobots@google.com>
Commit-Queue: Alexei Filippov <alph@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56354}

src/profiler/sampling-heap-profiler.cc

@@ -6,8 +6,10 @@
 
 #include <stdint.h>
 #include <memory>
+
 #include "src/api-inl.h"
 #include "src/base/ieee754.h"
+#include "src/base/template-utils.h"
 #include "src/base/utils/random-number-generator.h"
 #include "src/frames-inl.h"
 #include "src/heap/heap.h"
@@ -61,7 +63,6 @@ SamplingHeapProfiler::SamplingHeapProfiler(
           heap->isolate()->random_number_generator())),
       names_(names),
       profile_root_(nullptr, "(root)", v8::UnboundScript::kNoScriptId, 0),
-      samples_(),
       stack_depth_(stack_depth),
       rate_(rate),
       flags_(flags) {
@@ -75,8 +76,6 @@ SamplingHeapProfiler::SamplingHeapProfiler(
 SamplingHeapProfiler::~SamplingHeapProfiler() {
   heap_->RemoveAllocationObserversFromAllSpaces(other_spaces_observer_.get(),
                                                 new_space_observer_.get());
-
-  samples_.clear();
 }
 
 
@@ -96,9 +95,9 @@ void SamplingHeapProfiler::SampleObject(Address soon_object, size_t size) {
 
   AllocationNode* node = AddStack();
   node->allocations_[size]++;
-  Sample* sample = new Sample(size, node, loc, this);
-  samples_.emplace(sample);
-  sample->global.SetWeak(sample, OnWeakCallback, WeakCallbackType::kParameter);
+  auto sample = base::make_unique<Sample>(size, node, loc, this);
+  sample->global.SetWeak(sample.get(), OnWeakCallback,
+                         WeakCallbackType::kParameter);
 #if __clang__
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wdeprecated"
@@ -109,6 +108,7 @@ void SamplingHeapProfiler::SampleObject(Address soon_object, size_t size) {
 #if __clang__
 #pragma clang diagnostic pop
 #endif
+  samples_.emplace(sample.get(), std::move(sample));
 }
 
 void SamplingHeapProfiler::OnWeakCallback(
@@ -129,13 +129,7 @@ void SamplingHeapProfiler::OnWeakCallback(
       node = parent;
     }
   }
-  auto it = std::find_if(sample->profiler->samples_.begin(),
-                         sample->profiler->samples_.end(),
-                         [&sample](const std::unique_ptr<Sample>& s) {
-                           return s.get() == sample;
-                         });
-
-  sample->profiler->samples_.erase(it);
+  sample->profiler->samples_.erase(sample);
   // sample is deleted because its unique ptr was erased from samples_.
 }
 

src/profiler/sampling-heap-profiler.h

@@ -8,7 +8,7 @@
 #include <deque>
 #include <map>
 #include <memory>
-#include <set>
+#include <unordered_map>
 #include "include/v8-profiler.h"
 #include "src/heap/heap.h"
 #include "src/profiler/strings-storage.h"
@@ -146,7 +146,7 @@ class SamplingHeapProfiler {
   std::unique_ptr<SamplingAllocationObserver> other_spaces_observer_;
   StringsStorage* const names_;
   AllocationNode profile_root_;
-  std::set<std::unique_ptr<Sample>> samples_;
+  std::unordered_map<Sample*, std::unique_ptr<Sample>> samples_;
   const int stack_depth_;
   const uint64_t rate_;
   v8::HeapProfiler::SamplingFlags flags_;