slab_allocator: remove SlabAllocator

Now that Buffer instantiation has improved, the SlabAllocator is an
unnecessary layer of complexity preventing further performance
optimizations.

Currently there is a small performance loss with very small stream
requests, but this will soon be addressed.

node.gyp

@@ -108,7 +108,6 @@
         'src/smalloc.cc',
         'src/string_bytes.cc',
         'src/stream_wrap.cc',
-        'src/slab_allocator.cc',
         'src/tcp_wrap.cc',
         'src/timer_wrap.cc',
         'src/tty_wrap.cc',
@@ -140,7 +139,6 @@
         'src/tcp_wrap.h',
         'src/udp_wrap.h',
         'src/req_wrap.h',
-        'src/slab_allocator.h',
         'src/string_bytes.h',
         'src/stream_wrap.h',
         'src/tree.h',

src/slab_allocator.cc

@@ -1,127 +0,0 @@
-// Copyright Joyent, Inc. and other Node contributors.
-//
-// Permission is hereby granted, free of charge, to any person obtaining a
-// copy of this software and associated documentation files (the
-// "Software"), to deal in the Software without restriction, including
-// without limitation the rights to use, copy, modify, merge, publish,
-// distribute, sublicense, and/or sell copies of the Software, and to permit
-// persons to whom the Software is furnished to do so, subject to the
-// following conditions:
-//
-// The above copyright notice and this permission notice shall be included
-// in all copies or substantial portions of the Software.
-//
-// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
-// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
-// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
-// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
-// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
-// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
-// USE OR OTHER DEALINGS IN THE SOFTWARE.
-
-#include "v8.h"
-#include "node.h"
-#include "node_buffer.h"
-#include "slab_allocator.h"
-#include <stdio.h>
-#include <stdlib.h>
-#include <assert.h>
-
-
-using v8::Handle;
-using v8::HandleScope;
-using v8::Integer;
-using v8::Local;
-using v8::Null;
-using v8::Object;
-using v8::Persistent;
-using v8::String;
-using v8::V8;
-using v8::Value;
-
-
-namespace node {
-
-SlabAllocator::SlabAllocator(unsigned int size) {
-  size_ = ROUND_UP(size ? size : 1, 8192);
-  initialized_ = false;
-}
-
-
-SlabAllocator::~SlabAllocator() {
-  if (!initialized_) return;
-  if (V8::IsDead()) return;
-  slab_sym_.Dispose(node_isolate);
-  slab_sym_.Clear();
-  slab_.Dispose(node_isolate);
-  slab_.Clear();
-}
-
-
-void SlabAllocator::Initialize() {
-  HandleScope scope(node_isolate);
-  char sym[256];
-  snprintf(sym, sizeof(sym), "slab_%p", this); // namespace object key
-  offset_ = 0;
-  last_ptr_ = NULL;
-  initialized_ = true;
-  slab_sym_ = Persistent<String>::New(node_isolate, String::New(sym));
-}
-
-
-static Local<Object> NewSlab(unsigned int size) {
-  HandleScope scope(node_isolate);
-  Local<Object> buf = Buffer::New(ROUND_UP(size, 16));
-  return scope.Close(buf);
-}
-
-
-char* SlabAllocator::Allocate(Handle<Object> obj, unsigned int size) {
-  HandleScope scope(node_isolate);
-
-  assert(!obj.IsEmpty());
-
-  if (size == 0) return NULL;
-  if (!initialized_) Initialize();
-
-  if (size > size_) {
-    Local<Object> buf = NewSlab(size);
-    obj->SetHiddenValue(slab_sym_, buf);
-    return Buffer::Data(buf);
-  }
-
-  if (slab_.IsEmpty() || offset_ + size > size_) {
-    slab_.Dispose(node_isolate);
-    slab_.Clear();
-    slab_ = Persistent<Object>::New(node_isolate, NewSlab(size_));
-    offset_ = 0;
-    last_ptr_ = NULL;
-  }
-
-  obj->SetHiddenValue(slab_sym_, slab_);
-  last_ptr_ = Buffer::Data(slab_) + offset_;
-  offset_ += size;
-
-  return last_ptr_;
-}
-
-
-Local<Object> SlabAllocator::Shrink(Handle<Object> obj,
-                                    char* ptr,
-                                    unsigned int size) {
-  HandleScope scope(node_isolate);
-  Local<Value> slab_v = obj->GetHiddenValue(slab_sym_);
-  obj->SetHiddenValue(slab_sym_, Null(node_isolate));
-  assert(!slab_v.IsEmpty());
-  assert(slab_v->IsObject());
-  Local<Object> slab = slab_v->ToObject();
-  assert(ptr != NULL);
-  if (ptr == last_ptr_) {
-    last_ptr_ = NULL;
-    offset_ = ptr - Buffer::Data(slab) + ROUND_UP(size, 16);
-  }
-  return scope.Close(slab);
-}
-
-
-} // namespace node

src/slab_allocator.h

@@ -1,49 +0,0 @@
-// Copyright Joyent, Inc. and other Node contributors.
-//
-// Permission is hereby granted, free of charge, to any person obtaining a
-// copy of this software and associated documentation files (the
-// "Software"), to deal in the Software without restriction, including
-// without limitation the rights to use, copy, modify, merge, publish,
-// distribute, sublicense, and/or sell copies of the Software, and to permit
-// persons to whom the Software is furnished to do so, subject to the
-// following conditions:
-//
-// The above copyright notice and this permission notice shall be included
-// in all copies or substantial portions of the Software.
-//
-// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
-// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
-// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
-// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
-// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
-// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
-// USE OR OTHER DEALINGS IN THE SOFTWARE.
-
-#include "v8.h"
-
-namespace node {
-
-class SlabAllocator {
-public:
-  SlabAllocator(unsigned int size = 10485760); // default to 10M
-  ~SlabAllocator();
-
-  // allocate memory from slab, attaches the slice to `obj`
-  char* Allocate(v8::Handle<v8::Object> obj, unsigned int size);
-
-  // return excess memory to the slab, returns a handle to the parent buffer
-  v8::Local<v8::Object> Shrink(v8::Handle<v8::Object> obj,
-                               char* ptr,
-                               unsigned int size);
-
-private:
-  void Initialize();
-  bool initialized_;
-  v8::Persistent<v8::Object> slab_;
-  v8::Persistent<v8::String> slab_sym_;
-  unsigned int offset_;
-  unsigned int size_;
-  char* last_ptr_;
-};
-
-} // namespace node

src/stream_wrap.cc

@@ -22,7 +22,6 @@
 #include "node.h"
 #include "node_buffer.h"
 #include "handle_wrap.h"
-#include "slab_allocator.h"
 #include "stream_wrap.h"
 #include "pipe_wrap.h"
 #include "tcp_wrap.h"
@@ -33,8 +32,6 @@
 #include <stdlib.h> // abort()
 #include <limits.h> // INT_MAX
 
-#define SLAB_SIZE (1024 * 1024)
-
 
 namespace node {
 
@@ -49,6 +46,7 @@ using v8::Number;
 using v8::Object;
 using v8::Persistent;
 using v8::String;
+using v8::Uint32;
 using v8::Value;
 
 
@@ -58,23 +56,13 @@ static Persistent<String> write_queue_size_sym;
 static Persistent<String> onread_sym;
 static Persistent<String> oncomplete_sym;
 static Persistent<String> handle_sym;
-static SlabAllocator* slab_allocator;
 static bool initialized;
 
 
-static void DeleteSlabAllocator(void*) {
-  delete slab_allocator;
-  slab_allocator = NULL;
-}
-
-
 void StreamWrap::Initialize(Handle<Object> target) {
   if (initialized) return;
   initialized = true;
 
-  slab_allocator = new SlabAllocator(SLAB_SIZE);
-  AtExit(DeleteSlabAllocator, NULL);
-
   HandleScope scope(node_isolate);
 
   HandleWrap::Initialize(target);
@@ -592,8 +580,7 @@ void StreamWrapCallbacks::AfterWrite(WriteWrap* w) {
 
 uv_buf_t StreamWrapCallbacks::DoAlloc(uv_handle_t* handle,
                                       size_t suggested_size) {
-  char* buf = slab_allocator->Allocate(wrap_->object_, suggested_size);
+  return uv_buf_init(new char[suggested_size], suggested_size);
-  return uv_buf_init(buf, suggested_size);
 }
 
 
@@ -604,26 +591,30 @@ void StreamWrapCallbacks::DoRead(uv_stream_t* handle,
   HandleScope scope(node_isolate);
 
   if (nread < 0)  {
-    // If libuv reports an error or EOF it *may* give us a buffer back. In that
-    // case, return the space to the slab.
     if (buf.base != NULL)
-      slab_allocator->Shrink(Self(), buf.base, 0);
+      delete[] buf.base;
 
     SetErrno(uv_last_error(uv_default_loop()));
     MakeCallback(Self(), onread_sym, 0, NULL);
     return;
   }
 
-  Local<Object> slab = slab_allocator->Shrink(wrap_->object_, buf.base, nread);
+  if (nread == 0) {
+    if (buf.base != NULL)
+      delete[] buf.base;
+    return;
+  }
+
+  // TODO(trevnorris): not kosher to use new/delete w/ realloc
+  buf.base = static_cast<char*>(realloc(buf.base, nread));
 
-  if (nread == 0) return;
   assert(static_cast<size_t>(nread) <= buf.len);
 
   int argc = 3;
   Local<Value> argv[4] = {
-    slab,
+    Buffer::Use(buf.base, nread),
-    Integer::NewFromUnsigned(buf.base - Buffer::Data(slab), node_isolate),
+    Uint32::New(0, node_isolate),
-    Integer::NewFromUnsigned(nread, node_isolate)
+    Uint32::New(nread, node_isolate)
   };
 
   Local<Object> pending_obj;

src/stream_wrap.h

@@ -135,8 +135,6 @@ class StreamWrap : public HandleWrap {
   void UpdateWriteQueueSize();
 
  private:
-  static inline char* NewSlab(v8::Handle<v8::Object> global, v8::Handle<v8::Object> wrap_obj);
-
   // Callbacks for libuv
   static void AfterWrite(uv_write_t* req, int status);
   static uv_buf_t OnAlloc(uv_handle_t* handle, size_t suggested_size);
@@ -151,7 +149,6 @@ class StreamWrap : public HandleWrap {
   template <enum encoding encoding>
   static v8::Handle<v8::Value> WriteStringImpl(const v8::Arguments& args);
 
-  size_t slab_offset_;
   uv_stream_t* stream_;
 
   StreamWrapCallbacks default_callbacks_;

src/udp_wrap.cc

@@ -21,15 +21,12 @@
 
 #include "node.h"
 #include "node_buffer.h"
-#include "slab_allocator.h"
 #include "req_wrap.h"
 #include "handle_wrap.h"
 #include "udp_wrap.h"
 
 #include <stdlib.h>
 
-#define SLAB_SIZE (1024 * 1024)
-
 
 namespace node {
 
@@ -45,6 +42,7 @@ using v8::Object;
 using v8::Persistent;
 using v8::PropertyAttribute;
 using v8::String;
+using v8::Uint32;
 using v8::Value;
 
 typedef ReqWrap<uv_udp_send_t> SendWrap;
@@ -56,13 +54,6 @@ static Persistent<Function> constructor;
 static Persistent<String> buffer_sym;
 static Persistent<String> oncomplete_sym;
 static Persistent<String> onmessage_sym;
-static SlabAllocator* slab_allocator;
-
-
-static void DeleteSlabAllocator(void*) {
-  delete slab_allocator;
-  slab_allocator = NULL;
-}
 
 
 UDPWrap::UDPWrap(Handle<Object> object)
@@ -79,9 +70,6 @@ UDPWrap::~UDPWrap() {
 void UDPWrap::Initialize(Handle<Object> target) {
   HandleWrap::Initialize(target);
 
-  slab_allocator = new SlabAllocator(SLAB_SIZE);
-  AtExit(DeleteSlabAllocator, NULL);
-
   HandleScope scope(node_isolate);
 
   buffer_sym = NODE_PSYMBOL("buffer");
@@ -383,9 +371,7 @@ void UDPWrap::OnSend(uv_udp_send_t* req, int status) {
 
 
 uv_buf_t UDPWrap::OnAlloc(uv_handle_t* handle, size_t suggested_size) {
-  UDPWrap* wrap = static_cast<UDPWrap*>(handle->data);
+  return uv_buf_init(new char[suggested_size], suggested_size);
-  char* buf = slab_allocator->Allocate(wrap->object_, suggested_size);
-  return uv_buf_init(buf, suggested_size);
 }
 
 
@@ -397,23 +383,30 @@ void UDPWrap::OnRecv(uv_udp_t* handle,
   HandleScope scope(node_isolate);
 
   UDPWrap* wrap = reinterpret_cast<UDPWrap*>(handle->data);
-  Local<Object> slab = slab_allocator->Shrink(wrap->object_,
-                                              buf.base,
-                                              nread < 0 ? 0 : nread);
-  if (nread == 0) return;
 
   if (nread < 0) {
+    if (buf.base != NULL)
+      delete[] buf.base;
     Local<Value> argv[] = { Local<Object>::New(node_isolate, wrap->object_) };
     SetErrno(uv_last_error(uv_default_loop()));
     MakeCallback(wrap->object_, onmessage_sym, ARRAY_SIZE(argv), argv);
     return;
   }
 
+  if (nread == 0) {
+    if (buf.base != NULL)
+      delete[] buf.base;
+    return;
+  }
+
+  // TODO(trevnorris): not kosher to use new/delete w/ realloc
+  buf.base = static_cast<char*>(realloc(buf.base, nread));
+
   Local<Value> argv[] = {
     Local<Object>::New(node_isolate, wrap->object_),
-    slab,
+    Buffer::Use(buf.base, nread),
-    Integer::NewFromUnsigned(buf.base - Buffer::Data(slab), node_isolate),
+    Uint32::New(0, node_isolate),
-    Integer::NewFromUnsigned(nread, node_isolate),
+    Uint32::New(nread, node_isolate),
     AddressToJS(addr)
   };
   MakeCallback(wrap->object_, onmessage_sym, ARRAY_SIZE(argv), argv);