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core: add reusable slab allocator

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1 parent a58659c commit 08032efed00bb798cb9e1b4aaa0b626fc87d78cc @bnoordhuis bnoordhuis committed Mar 28, 2012
Showing with 178 additions and 0 deletions.
  1. +2 −0 node.gyp
  2. +127 −0 src/slab_allocator.cc
  3. +49 −0 src/slab_allocator.h
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@@ -84,6 +84,7 @@
'src/node_zlib.cc',
'src/pipe_wrap.cc',
'src/stream_wrap.cc',
+ 'src/slab_allocator.cc',
'src/tcp_wrap.cc',
'src/timer_wrap.cc',
'src/tty_wrap.cc',
@@ -107,6 +108,7 @@
'src/node_version.h',
'src/pipe_wrap.h',
'src/req_wrap.h',
+ 'src/slab_allocator.h',
'src/stream_wrap.h',
'src/v8_typed_array.h',
'deps/http_parser/http_parser.h',
View
@@ -0,0 +1,127 @@
+// 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::Value;
+
+
+namespace node {
+
+SlabAllocator::SlabAllocator(unsigned int size) {
+ size_ = ROUND_UP(size ? size : 1, 8192);
+ initialized_ = false;
+}
+
+
+SlabAllocator::~SlabAllocator() {
+ if (!initialized_) return;
+ slab_sym_.Clear();
+ slab_sym_.Dispose();
+ slab_.Clear();
+ slab_.Dispose();
+}
+
+
+void SlabAllocator::Initialize() {
+ HandleScope scope;
+ 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(String::New(sym));
+}
+
+
+static Local<Object> NewSlab(unsigned int size) {
+ HandleScope scope;
+ Local<Value> arg = Integer::NewFromUnsigned(ROUND_UP(size, 16));
+ Local<Object> buf = Buffer::constructor_template
+ ->GetFunction()
+ ->NewInstance(1, &arg);
+ return scope.Close(buf);
+}
+
+
+char* SlabAllocator::Allocate(Handle<Object> obj, unsigned int size) {
+ HandleScope scope;
+
+ 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_.Clear();
+ slab_.Dispose();
+ slab_ = Persistent<Object>::New(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;
+ Local<Value> slab_v = obj->GetHiddenValue(slab_sym_);
+ obj->SetHiddenValue(slab_sym_, Null());
+ assert(!slab_v.IsEmpty());
+ assert(slab_v->IsObject());
+ Local<Object> slab = slab_v->ToObject();
+ if (ptr && ptr == last_ptr_) {
+ last_ptr_ = NULL;
+ offset_ = ptr - Buffer::Data(slab) + ROUND_UP(size, 16);
+ }
+ return scope.Close(slab);
+}
+
+
+} // namespace node
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@@ -0,0 +1,49 @@
+// 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

2 comments on commit 08032ef

This is nice, and I may have a use for this in my project.

Would it make sense to expose this, or is it a better idea to have a pure-JS version of this in NPM?

Never mind, I just discovered that buffer.js already does this sort of thing.

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