Reland: Create libsampler as V8 sampler library.

This patch does five things:

1. Extracts sampler as libsampler to provide sampling functionality support.
2. Makes SampleStack virtual so embedders can override the behaviour of sample collecting.
3. Removes sampler.[h|cc].
4. Moves sampling thread into log.cc as workaround to keep the --prof functionality.
5. Creates SamplerManager to manage the relationship between samplers and threads.

The reason we port hashmap.h is that in debug mode, STL containers are using
mutexes from a mutex pool, which may lead to deadlock when using asynchronously
signal handler.

Currently libsampler is used in V8 temporarily.

BUG=v8:4789
LOG=n

Committed: https://crrev.com/06cc9b7c176a6223971deaa9fbcafe1a05058c7b
Cr-Commit-Position: refs/heads/master@{#36527}

Review-Url: https://codereview.chromium.org/1922303002
Cr-Commit-Position: refs/heads/master@{#36532}

BUILD.gn

@@ -105,6 +105,11 @@ config("libplatform_config") {
   include_dirs = [ "include" ]
 }
 
+# This config should be applied to code using the libsampler.
+config("libsampler_config") {
+  include_dirs = [ "include" ]
+}
+
 # This config should only be applied to code using V8 and not any V8 code
 # itself.
 config("external_config") {
@@ -1329,8 +1334,6 @@ v8_source_set("v8_base") {
     "src/profiler/profile-generator-inl.h",
     "src/profiler/profile-generator.cc",
     "src/profiler/profile-generator.h",
-    "src/profiler/sampler.cc",
-    "src/profiler/sampler.h",
     "src/profiler/sampling-heap-profiler.cc",
     "src/profiler/sampling-heap-profiler.h",
     "src/profiler/strings-storage.cc",
@@ -1816,6 +1819,7 @@ v8_source_set("v8_base") {
   defines = []
   deps = [
     ":v8_libbase",
+    ":v8_libsampler",
   ]
 
   if (is_win) {
@@ -1970,6 +1974,23 @@ v8_source_set("v8_libplatform") {
   ]
 }
 
+v8_source_set("v8_libsampler") {
+  sources = [
+    "src/libsampler/hashmap.h",
+    "src/libsampler/utils.h",
+    "src/libsampler/v8-sampler.cc",
+    "src/libsampler/v8-sampler.h",
+  ]
+
+  configs = [ ":internal_config_base" ]
+
+  public_configs = [ ":libsampler_config" ]
+
+  deps = [
+    ":v8_libbase",
+  ]
+}
+
 v8_source_set("fuzzer_support") {
   visibility = [ ":*" ]  # Only targets in this file can depend on this.
 

include/v8.h

@@ -6331,6 +6331,12 @@ class V8_EXPORT Isolate {
    */
   void VisitWeakHandles(PersistentHandleVisitor* visitor);
 
+  /**
+   * Check if this isolate is in use.
+   * True if at least one thread Enter'ed this isolate.
+   */
+  bool IsInUse();
+
  private:
   template <class K, class V, class Traits>
   friend class PersistentValueMapBase;

src/api.cc

@@ -7793,6 +7793,12 @@ void Isolate::VisitExternalResources(ExternalResourceVisitor* visitor) {
 }
 
 
+bool Isolate::IsInUse() {
+  i::Isolate* isolate = reinterpret_cast<i::Isolate*>(this);
+  return isolate->IsInUse();
+}
+
+
 class VisitorAdapter : public i::ObjectVisitor {
  public:
   explicit VisitorAdapter(PersistentHandleVisitor* visitor)

src/isolate.cc

@@ -27,10 +27,10 @@
 #include "src/ic/stub-cache.h"
 #include "src/interpreter/interpreter.h"
 #include "src/isolate-inl.h"
+#include "src/libsampler/v8-sampler.h"
 #include "src/log.h"
 #include "src/messages.h"
 #include "src/profiler/cpu-profiler.h"
-#include "src/profiler/sampler.h"
 #include "src/prototype.h"
 #include "src/regexp/regexp-stack.h"
 #include "src/runtime-profiler.h"
@@ -2006,7 +2006,7 @@ void Isolate::Deinit() {
   }
 
   // We must stop the logger before we tear down other components.
-  Sampler* sampler = logger_->sampler();
+  sampler::Sampler* sampler = logger_->sampler();
   if (sampler && sampler->IsActive()) sampler->Stop();
 
   delete deoptimizer_data_;

src/libsampler/DEPS

@@ -0,0 +1,6 @@
+include_rules = [
+  "+include",
+  "-src",
+  "+src/base",
+  "+src/libsampler",
+]

src/libsampler/hashmap.h

@@ -0,0 +1,278 @@
+// Copyright 2012 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// This file is ported from src/hashmap.h
+
+#ifndef V8_LIBSAMPLER_HASHMAP_H_
+#define V8_LIBSAMPLER_HASHMAP_H_
+
+#include "src/base/bits.h"
+#include "src/base/logging.h"
+#include "src/libsampler/utils.h"
+
+namespace v8 {
+namespace sampler {
+
+class HashMapImpl {
+ public:
+  typedef bool (*MatchFun) (void* key1, void* key2);
+
+  // The default capacity.
+  static const uint32_t kDefaultHashMapCapacity = 8;
+
+  // initial_capacity is the size of the initial hash map;
+  // it must be a power of 2 (and thus must not be 0).
+  HashMapImpl(MatchFun match,
+              uint32_t capacity = kDefaultHashMapCapacity);
+
+  ~HashMapImpl();
+
+  // HashMap entries are (key, value, hash) triplets.
+  // Some clients may not need to use the value slot
+  // (e.g. implementers of sets, where the key is the value).
+  struct Entry {
+    void* key;
+    void* value;
+    uint32_t hash;  // The full hash value for key
+    int order;  // If you never remove entries this is the insertion order.
+  };
+
+  // If an entry with matching key is found, returns that entry.
+  // Otherwise, NULL is returned.
+  Entry* Lookup(void* key, uint32_t hash) const;
+
+  // If an entry with matching key is found, returns that entry.
+  // If no matching entry is found, a new entry is inserted with
+  // corresponding key, key hash, and NULL value.
+  Entry* LookupOrInsert(void* key, uint32_t hash);
+
+  // Removes the entry with matching key.
+  // It returns the value of the deleted entry
+  // or null if there is no value for such key.
+  void* Remove(void* key, uint32_t hash);
+
+  // Empties the hash map (occupancy() == 0).
+  void Clear();
+
+  // The number of (non-empty) entries in the table.
+  uint32_t occupancy() const { return occupancy_; }
+
+  // The capacity of the table. The implementation
+  // makes sure that occupancy is at most 80% of
+  // the table capacity.
+  uint32_t capacity() const { return capacity_; }
+
+  // Iteration
+  //
+  // for (Entry* p = map.Start(); p != NULL; p = map.Next(p)) {
+  //   ...
+  // }
+  //
+  // If entries are inserted during iteration, the effect of
+  // calling Next() is undefined.
+  Entry* Start() const;
+  Entry* Next(Entry* p) const;
+
+  // Some match functions defined for convenience.
+  static bool PointersMatch(void* key1, void* key2) {
+    return key1 == key2;
+  }
+
+ private:
+  MatchFun match_;
+  Entry* map_;
+  uint32_t capacity_;
+  uint32_t occupancy_;
+
+  Entry* map_end() const { return map_ + capacity_; }
+  Entry* Probe(void* key, uint32_t hash) const;
+  void Initialize(uint32_t capacity);
+  void Resize();
+};
+
+typedef HashMapImpl HashMap;
+
+HashMapImpl::HashMapImpl(MatchFun match, uint32_t initial_capacity) {
+  match_ = match;
+  Initialize(initial_capacity);
+}
+
+
+HashMapImpl::~HashMapImpl() {
+  Malloced::Delete(map_);
+}
+
+
+HashMapImpl::Entry* HashMapImpl::Lookup(void* key, uint32_t hash) const {
+  Entry* p = Probe(key, hash);
+  return p->key != NULL ? p : NULL;
+}
+
+
+HashMapImpl::Entry* HashMapImpl::LookupOrInsert(void* key, uint32_t hash) {
+  // Find a matching entry.
+  Entry* p = Probe(key, hash);
+  if (p->key != NULL) {
+    return p;
+  }
+
+  // No entry found; insert one.
+  p->key = key;
+  p->value = NULL;
+  p->hash = hash;
+  p->order = occupancy_;
+  occupancy_++;
+
+  // Grow the map if we reached >= 80% occupancy.
+  if (occupancy_ + occupancy_ / 4 >= capacity_) {
+    Resize();
+    p = Probe(key, hash);
+  }
+
+  return p;
+}
+
+
+void* HashMapImpl::Remove(void* key, uint32_t hash) {
+  // Lookup the entry for the key to remove.
+  Entry* p = Probe(key, hash);
+  if (p->key == NULL) {
+    // Key not found nothing to remove.
+    return NULL;
+  }
+
+  void* value = p->value;
+  // To remove an entry we need to ensure that it does not create an empty
+  // entry that will cause the search for another entry to stop too soon. If all
+  // the entries between the entry to remove and the next empty slot have their
+  // initial position inside this interval, clearing the entry to remove will
+  // not break the search. If, while searching for the next empty entry, an
+  // entry is encountered which does not have its initial position between the
+  // entry to remove and the position looked at, then this entry can be moved to
+  // the place of the entry to remove without breaking the search for it. The
+  // entry made vacant by this move is now the entry to remove and the process
+  // starts over.
+  // Algorithm from http://en.wikipedia.org/wiki/Open_addressing.
+
+  // This guarantees loop termination as there is at least one empty entry so
+  // eventually the removed entry will have an empty entry after it.
+  DCHECK(occupancy_ < capacity_);
+
+  // p is the candidate entry to clear. q is used to scan forwards.
+  Entry* q = p;  // Start at the entry to remove.
+  while (true) {
+    // Move q to the next entry.
+    q = q + 1;
+    if (q == map_end()) {
+      q = map_;
+    }
+
+    // All entries between p and q have their initial position between p and q
+    // and the entry p can be cleared without breaking the search for these
+    // entries.
+    if (q->key == NULL) {
+      break;
+    }
+
+    // Find the initial position for the entry at position q.
+    Entry* r = map_ + (q->hash & (capacity_ - 1));
+
+    // If the entry at position q has its initial position outside the range
+    // between p and q it can be moved forward to position p and will still be
+    // found. There is now a new candidate entry for clearing.
+    if ((q > p && (r <= p || r > q)) ||
+        (q < p && (r <= p && r > q))) {
+      *p = *q;
+      p = q;
+    }
+  }
+
+  // Clear the entry which is allowed to en emptied.
+  p->key = NULL;
+  occupancy_--;
+  return value;
+}
+
+
+void HashMapImpl::Clear() {
+  // Mark all entries as empty.
+  const Entry* end = map_end();
+  for (Entry* p = map_; p < end; p++) {
+    p->key = NULL;
+  }
+  occupancy_ = 0;
+}
+
+
+HashMapImpl::Entry* HashMapImpl::Start() const {
+  return Next(map_ - 1);
+}
+
+
+HashMapImpl::Entry* HashMapImpl::Next(Entry* p) const {
+  const Entry* end = map_end();
+  DCHECK(map_ - 1 <= p && p < end);
+  for (p++; p < end; p++) {
+    if (p->key != NULL) {
+      return p;
+    }
+  }
+  return NULL;
+}
+
+
+HashMapImpl::Entry* HashMapImpl::Probe(void* key, uint32_t hash) const {
+  DCHECK(key != NULL);
+
+  DCHECK(base::bits::IsPowerOfTwo32(capacity_));
+  Entry* p = map_ + (hash & (capacity_ - 1));
+  const Entry* end = map_end();
+  DCHECK(map_ <= p && p < end);
+
+  DCHECK(occupancy_ < capacity_);  // Guarantees loop termination.
+  while (p->key != NULL && (hash != p->hash || !match_(key, p->key))) {
+    p++;
+    if (p >= end) {
+      p = map_;
+    }
+  }
+
+  return p;
+}
+
+
+void HashMapImpl::Initialize(uint32_t capacity) {
+  DCHECK(base::bits::IsPowerOfTwo32(capacity));
+  map_ = reinterpret_cast<Entry*>(Malloced::New(capacity * sizeof(Entry)));
+  CHECK(map_ != NULL);
+  capacity_ = capacity;
+  Clear();
+}
+
+
+void HashMapImpl::Resize() {
+  Entry* map = map_;
+  uint32_t n = occupancy_;
+
+  // Allocate larger map.
+  Initialize(capacity_ * 2);
+
+  // Rehash all current entries.
+  for (Entry* p = map; n > 0; p++) {
+    if (p->key != NULL) {
+      Entry* entry = LookupOrInsert(p->key, p->hash);
+      entry->value = p->value;
+      entry->order = p->order;
+      n--;
+    }
+  }
+
+  // Delete old map.
+  Malloced::Delete(map);
+}
+
+}  // namespace sampler
+}  // namespace v8
+
+#endif  // V8_LIBSAMPLER_HASHMAP_H_