ASIO进行过多的小堆分配还是我错了?

希望有人能做出贡献…

此外,在我在Booo::Asio的实验中,我决定,在服务器应用程序启动和运行之后,我会在C++的“新”代码中设置一个断点,即在“new .CPP”@函数“Vaul*y-CRTDECL操作符new(SiZeSt大小)注意,我使用的是MSVC 2008。

使用上面的代码,原始邮件的 :

既然BP接通了,我要连接一个客户。
分配已完成(多次)(如预期的那样)(我知道这一点是因为调试器在我设置时停止在“new”关键字处),新客户机现在可以发送/接收数据了。
我从客户机向服务器发送“嗨”。
“new”处的bp在handle_read()处被点击。
到的源是对async_write()的调用(我用msvc堆栈跟踪)。
按F5(continue)会在“new”处生成另一个断点,这一次是由async_read_some()调用生成的。

结论: 每一个这样的操作都会生成一个对“new”的调用 !!!!!!!!最坏的情况是一个真正的服务器可能有!

因此,进一步寻找某种方法来使用某种内存池,这样这些“新”调用就不存在了,这让我想到了一个例子:“分配”。
路径:“…….\boost\u 1_43_0\libs\asio\example\allocation\”。

用这个新代码(写在下面)做同样的事情给了我 欢呼的结果 ;
对async_write()和async_read_some()的调用 不生成 呼叫“新”。

到目前为止,这很好,但老实说,我不能说我完全理解这是怎么做到的;正如您所看到的,分配器被分成了几个部分,这让我有点困惑。

使_custom_alloc_handler()<---它到底做什么?
从这个()共享了什么??
我看到“session”对象具有成员“handler_allocator allocator_uu”。每个“会话”对象是否都包含这些对象的池?!我可以在“服务器”类级别上使用其中的一个,它是共享的还是其他的?

“分配器”示例代码:

//
// server.cpp
// ~~~~~~~~~~
//
// Copyright (c) 2003-2010 Christopher M. Kohlhoff (chris at kohlhoff dot com)
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//

#include <cstdlib>
#include <iostream>
#include <boost/aligned_storage.hpp>
#include <boost/array.hpp>
#include <boost/bind.hpp>
#include <boost/enable_shared_from_this.hpp>
#include <boost/noncopyable.hpp>
#include <boost/shared_ptr.hpp>
#include <boost/asio.hpp>

using boost::asio::ip::tcp;

// Class to manage the memory to be used for handler-based custom allocation.
// It contains a single block of memory which may be returned for allocation
// requests. If the memory is in use when an allocation request is made, the
// allocator delegates allocation to the global heap.
class handler_allocator
    : private boost::noncopyable
{
public:
    handler_allocator()
        : in_use_(false)
    {
    }

    void* allocate(std::size_t size)
    {
        if (!in_use_ && size < storage_.size)
        {
            in_use_ = true;
            return storage_.address();
        }
        else
        {
            return ::operator new(size);
        }
    }

    void deallocate(void* pointer)
    {
        if (pointer == storage_.address())
        {
            in_use_ = false;
        }
        else
        {
            ::operator delete(pointer);
        }
    }

private:
    // Storage space used for handler-based custom memory allocation.
    boost::aligned_storage<1024> storage_;

    // Whether the handler-based custom allocation storage has been used.
    bool in_use_;
};

// Wrapper class template for handler objects to allow handler memory
// allocation to be customised. Calls to operator() are forwarded to the
// encapsulated handler.
template <typename Handler>
class custom_alloc_handler
{
public:
    custom_alloc_handler(handler_allocator& a, Handler h)
        : allocator_(a),
        handler_(h)
    {
    }

    template <typename Arg1>
    void operator()(Arg1 arg1)
    {
        handler_(arg1);
    }

    template <typename Arg1, typename Arg2>
    void operator()(Arg1 arg1, Arg2 arg2)
    {
        handler_(arg1, arg2);
    }

    friend void* asio_handler_allocate(std::size_t size,
        custom_alloc_handler<Handler>* this_handler)
    {
        return this_handler->allocator_.allocate(size);
    }

    friend void asio_handler_deallocate(void* pointer, std::size_t /*size*/,
        custom_alloc_handler<Handler>* this_handler)
    {
        this_handler->allocator_.deallocate(pointer);
    }

private:
    handler_allocator& allocator_;
    Handler handler_;
};

// Helper function to wrap a handler object to add custom allocation.
template <typename Handler>
inline custom_alloc_handler<Handler> make_custom_alloc_handler(
    handler_allocator& a, Handler h)
{
    return custom_alloc_handler<Handler>(a, h);
}

class session
    : public boost::enable_shared_from_this<session>
{
public:
    session(boost::asio::io_service& io_service)
        : socket_(io_service)
    {
    }

    tcp::socket& socket()
    {
        return socket_;
    }

    void start()
    {
        socket_.async_read_some(boost::asio::buffer(data_),
            make_custom_alloc_handler(allocator_,
            boost::bind(&session::handle_read,
            shared_from_this(),
            boost::asio::placeholders::error,
            boost::asio::placeholders::bytes_transferred)));
    }

    void handle_read(const boost::system::error_code& error,
        size_t bytes_transferred)
    {
        if (!error)
        {
            boost::asio::async_write(socket_,
                boost::asio::buffer(data_, bytes_transferred),
                make_custom_alloc_handler(allocator_, boost::bind(&session::handle_write, shared_from_this(), boost::asio::placeholders::error))
                );
        }
    }

    void handle_write(const boost::system::error_code& error)
    {
        if (!error)
        {
            socket_.async_read_some(boost::asio::buffer(data_),
                make_custom_alloc_handler(allocator_,
                boost::bind(&session::handle_read,
                shared_from_this(),
                boost::asio::placeholders::error,
                boost::asio::placeholders::bytes_transferred)));
        }
    }

private:
    // The socket used to communicate with the client.
    tcp::socket socket_;

    // Buffer used to store data received from the client.
    boost::array<char, 1024> data_;

    // The allocator to use for handler-based custom memory allocation.
    handler_allocator allocator_;
};

typedef boost::shared_ptr<session> session_ptr;

class server
{
public:
    server(boost::asio::io_service& io_service, short port)
        : io_service_(io_service),
        acceptor_(io_service, tcp::endpoint(tcp::v4(), port))
    {
        session_ptr new_session(new session(io_service_));
        acceptor_.async_accept(new_session->socket(),
            boost::bind(&server::handle_accept, this, new_session,
            boost::asio::placeholders::error));
    }

    void handle_accept(session_ptr new_session,
        const boost::system::error_code& error)
    {
        if (!error)
        {
            new_session->start();
            new_session.reset(new session(io_service_));
            acceptor_.async_accept(new_session->socket(),
                boost::bind(&server::handle_accept, this, new_session,
                boost::asio::placeholders::error));
        }
    }

private:
    boost::asio::io_service& io_service_;
    tcp::acceptor acceptor_;
};

int main(int argc, char* argv[])
{
    try
    {
        if (argc != 2)
        {
            std::cerr << "Usage: server <port>\n";
            return 1;
        }

        boost::asio::io_service io_service;

        using namespace std; // For atoi.
        server s(io_service, atoi(argv[1]));

        io_service.run();
    }
    catch (std::exception& e)
    {
        std::cerr << "Exception: " << e.what() << "\n";
    }

    return 0;
}

要回答第二个问题,您可以使用IO服务::Post,方法是给它一个绑定到session::handle_read的boost::bind参数以及您想要的任何错误代码。