uhd/host/lib/transport/zero_copy_flow_ctrl.cpp

//
// Copyright 2017 Ettus Research
// Copyright 2018 Ettus Research, a National Instruments Company
//
// SPDX-License-Identifier: GPL-3.0-or-later
//

#include <uhd/transport/bounded_buffer.hpp>
#include <uhd/transport/buffer_pool.hpp>
#include <uhd/transport/zero_copy_flow_ctrl.hpp>
#include <uhd/utils/log.hpp>
#include <uhd/utils/safe_call.hpp>
#include <boost/format.hpp>
#include <boost/thread/mutex.hpp>
#include <boost/thread/thread.hpp>
#include <functional>
#include <memory>

using namespace uhd;
using namespace uhd::transport;

typedef bounded_buffer<managed_send_buffer::sptr> bounded_buffer_t;

class zero_copy_flow_ctrl_msb : public managed_send_buffer
{
public:
    zero_copy_flow_ctrl_msb(flow_ctrl_func flow_ctrl)
        : _mb(nullptr), _flow_ctrl(flow_ctrl)
    {
        /* NOP */
    }

    ~zero_copy_flow_ctrl_msb()
    {
        /* NOP */
    }

    void release()
    {
        if (_mb) {
            _mb->commit(size());
            while (_flow_ctrl and not _flow_ctrl(_mb)) {
            }
            _mb.reset();
        }
    }

    UHD_INLINE sptr get(sptr& mb)
    {
        _mb = mb;
        return make(this, _mb->cast<void*>(), _mb->size());
    }

private:
    sptr _mb;
    flow_ctrl_func _flow_ctrl;
};

class zero_copy_flow_ctrl_mrb : public managed_recv_buffer
{
public:
    zero_copy_flow_ctrl_mrb(flow_ctrl_func flow_ctrl) : _mb(NULL), _flow_ctrl(flow_ctrl)
    {
        /* NOP */
    }

    ~zero_copy_flow_ctrl_mrb()
    {
        /* NOP */
    }

    void release()
    {
        if (_mb) {
            _mb.reset();
        }
    }

    UHD_INLINE sptr get(sptr& mb)
    {
        _mb = mb;
        while (_flow_ctrl and not _flow_ctrl(_mb)) {
        }
        return make(this, _mb->cast<void*>(), _mb->size());
    }

private:
    sptr _mb;
    flow_ctrl_func _flow_ctrl;
};

/***********************************************************************
 * Zero copy offload transport:
 * An intermediate transport that utilizes threading to free
 * the main thread from any receive work.
 **********************************************************************/
class zero_copy_flow_ctrl_impl : public zero_copy_flow_ctrl
{
public:
    typedef std::shared_ptr<zero_copy_flow_ctrl_impl> sptr;

    zero_copy_flow_ctrl_impl(zero_copy_if::sptr transport,
        flow_ctrl_func send_flow_ctrl,
        flow_ctrl_func recv_flow_ctrl)
        : _transport(transport)
        , _send_buffers(transport->get_num_send_frames())
        , _recv_buffers(transport->get_num_recv_frames())
        , _send_buff_index(0)
        , _recv_buff_index(0)
        , _send_flow_ctrl(send_flow_ctrl)
        , _recv_flow_ctrl(recv_flow_ctrl)
    {
        UHD_LOG_TRACE("TRANSPORT", "Created zero_copy_flow_ctrl");

        for (size_t i = 0; i < transport->get_num_send_frames(); i++) {
            _send_buffers[i] = std::make_shared<zero_copy_flow_ctrl_msb>(_send_flow_ctrl);
        }
        for (size_t i = 0; i < transport->get_num_recv_frames(); i++) {
            _recv_buffers[i] = std::make_shared<zero_copy_flow_ctrl_mrb>(_recv_flow_ctrl);
        }
    }

    ~zero_copy_flow_ctrl_impl() {}

    /*******************************************************************
     * Receive implementation:
     * Pop the receive buffer pointer from the underlying transport
     ******************************************************************/
    UHD_INLINE managed_recv_buffer::sptr get_recv_buff(double timeout)
    {
        managed_recv_buffer::sptr ptr;
        managed_recv_buffer::sptr buff = _transport->get_recv_buff(timeout);
        if (buff) {
            std::shared_ptr<zero_copy_flow_ctrl_mrb> mb =
                _recv_buffers[_recv_buff_index++];
            _recv_buff_index %= _recv_buffers.size();
            ptr = mb->get(buff);
        }
        return ptr;
    }

    UHD_INLINE size_t get_num_recv_frames() const
    {
        return _transport->get_num_recv_frames();
    }

    UHD_INLINE size_t get_recv_frame_size() const
    {
        return _transport->get_recv_frame_size();
    }

    /*******************************************************************
     * Send implementation:
     * Pass the send buffer pointer from the underlying transport
     ******************************************************************/
    managed_send_buffer::sptr get_send_buff(double timeout)
    {
        managed_send_buffer::sptr ptr;
        managed_send_buffer::sptr buff = _transport->get_send_buff(timeout);
        if (buff) {
            std::shared_ptr<zero_copy_flow_ctrl_msb> mb =
                _send_buffers[_send_buff_index++];
            _send_buff_index %= _send_buffers.size();
            ptr = mb->get(buff);
        }
        return ptr;
    }

    UHD_INLINE size_t get_num_send_frames() const
    {
        return _transport->get_num_send_frames();
    }

    UHD_INLINE size_t get_send_frame_size() const
    {
        return _transport->get_send_frame_size();
    }

private:
    // The underlying transport
    zero_copy_if::sptr _transport;

    // buffers
    std::vector<std::shared_ptr<zero_copy_flow_ctrl_msb>> _send_buffers;
    std::vector<std::shared_ptr<zero_copy_flow_ctrl_mrb>> _recv_buffers;
    size_t _send_buff_index;
    size_t _recv_buff_index;

    // Flow control functions
    flow_ctrl_func _send_flow_ctrl;
    flow_ctrl_func _recv_flow_ctrl;
};

zero_copy_flow_ctrl::sptr zero_copy_flow_ctrl::make(zero_copy_if::sptr transport,
    flow_ctrl_func send_flow_ctrl,
    flow_ctrl_func recv_flow_ctrl)
{
    zero_copy_flow_ctrl_impl::sptr zero_copy_flow_ctrl(
        new zero_copy_flow_ctrl_impl(transport, send_flow_ctrl, recv_flow_ctrl));

    return zero_copy_flow_ctrl;
}