uhd: Introduce I/O service manager

- Implement I/O service detach link methods
- The I/O service manager instantiates new I/O services or connects
  links to existing I/O services based on options provided by the user
  in stream_args.
- Add a streamer ID parameter to methods to create transports so that
  the I/O service manager can group transports appropriately when using
  offload threads.
- Change X300 and MPMD to use I/O service manager to connect links to
  I/O services.
- There is now a single I/O service manager per rfnoc_graph (and it is
  also stored in the graph)
- The I/O service manager now also knows the device args for the
  rfnoc_graph it was created with, and can make decisions based upon
  those (e.g, use a specific I/O service for DPDK, share cores between
  streamers, etc.)
- The I/O Service Manager does not get any decision logic with this
  commit, though
- The MB ifaces for mpmd and x300 now access this global I/O service
  manager
- Add configuration of link parameters with overrides

Co-Authored-By: Martin Braun <martin.braun@ettus.com>
Co-Authored-By: Aaron Rossetto <aaron.rossetto@ni.com>

2 files changed, 197 insertions, 0 deletions

diff --git a/host/lib/include/uhdlib/usrp/common/io_service_args.hpp b/host/lib/include/uhdlib/usrp/common/io_service_args.hpp
new file mode 100644
index 000000000..a783cc825
--- /dev/null
+++ b/host/lib/include/uhdlib/usrp/common/io_service_args.hpp
@@ -0,0 +1,93 @@
+//
+// Copyright 2019 Ettus Research, a National Instruments brand
+//
+// SPDX-License-Identifier: GPL-3.0-or-later
+//
+
+#ifndef INCLUDED_LIBUHD_IO_SERVICE_ARGS_HPP
+#define INCLUDED_LIBUHD_IO_SERVICE_ARGS_HPP
+
+#include <uhd/types/device_addr.hpp>
+#include <boost/optional.hpp>
+
+namespace uhd { namespace usrp {
+
+/*! Struct containing user options for I/O services
+ *
+ * The I/O service manager supports the following args:
+ *
+ * recv_offload: set to "true" to use an offload thread for RX_DATA links, "false"
+ *               to use an inline I/O service.
+ * send_offload: set to "true" to use an offload thread for TX_DATA links, "false"
+ *               to use an inline I/O service.
+ * recv_offload_wait_mode: set to "poll" to use a polling strategy in the offload
+ *                         thread, set to "block" to use a blocking strategy.
+ * send_offload_wait_mode: set to "poll" to use a polling strategy in the offload
+ *                         thread, set to "block" to use a blocking strategy.
+ * num_poll_offload_threads: set to the total number of offload threads to use for
+ *                           RX_DATA and TX_DATA in this rfnoc_graph. New connections
+ *                           always go to the offload thread containing the fewest
+ *                           connections, with lowest numbered thread as a second
+ *                           criterion. The default is 1.
+ * recv_offload_cpu_<N>: an integer to specify cpu affinity of the offload thread.
+ *                       N indicates the thread instance, starting with 0 for each
+ *                       streamer and ending with the number of transport adapters
+ *                       minus one. Only used if the I/O service is configured to
+ *                       block.
+ * send_offload_cpu_<N>: an integer to specify cpu affinity of the offload thread.
+ *                       N indicates the thread instance, starting with 0 for each
+ *                       streamer and ending with the number of transport adapters
+ *                       minus one. Only used if the I/O service is configured to
+ *                       block.
+ * poll_offload_cpu_<N>: an integer to specify cpu affinity of the offload thread.
+ *                       N indicates the thread instance, starting with 0 and up to
+ *                       num_poll_offload_threads minus 1. Only used if the I/O
+ *                       service is configured to poll.
+ */
+struct io_service_args_t
+{
+    enum wait_mode_t { POLL, BLOCK };
+
+    //! Whether to offload streaming I/O to a worker thread
+    bool recv_offload = false;
+
+    //! Whether to offload streaming I/O to a worker thread
+    bool send_offload = false;
+
+    //! Whether the offload thread should poll or block
+    wait_mode_t recv_offload_wait_mode = BLOCK;
+
+    //! Whether the offload thread should poll or block
+    wait_mode_t send_offload_wait_mode = BLOCK;
+
+    //! Number of polling threads to use, if wait_mode is set to POLL
+    size_t num_poll_offload_threads = 1;
+
+    //! CPU affinity of offload threads, if wait_mode is set to BLOCK (one item
+    //! per thread)
+    std::vector<boost::optional<size_t>> recv_offload_thread_cpu;
+
+    //! CPU affinity of offload threads, if wait_mode is set to BLOCK (one item
+    //! per thread)
+    std::vector<boost::optional<size_t>> send_offload_thread_cpu;
+
+    //! CPU affinity of offload threads, if wait_mode is set to POLL (one item
+    //! per thread)
+    std::vector<boost::optional<size_t>> poll_offload_thread_cpu;
+};
+
+/*! Reads I/O service args from provided dictionary
+ *
+ * If an option is not specified in the dictionary, the default value of the
+ * struct above is returned.
+ *
+ * \param args The dictionary from which to read the I/O service args
+ * \param defaults Default values (not including boost::optional values)
+ * \return The I/O service args read
+ */
+io_service_args_t read_io_service_args(
+    const device_addr_t& args, const io_service_args_t& defaults);
+
+}} // namespace uhd::usrp
+
+#endif /* INCLUDED_LIBUHD_IO_SERVICE_ARGS_HPP */
diff --git a/host/lib/include/uhdlib/usrp/common/io_service_mgr.hpp b/host/lib/include/uhdlib/usrp/common/io_service_mgr.hpp
new file mode 100644
index 000000000..1093f7bec
--- /dev/null
+++ b/host/lib/include/uhdlib/usrp/common/io_service_mgr.hpp
@@ -0,0 +1,104 @@
+//
+// Copyright 2019 Ettus Research, a National Instruments Brand
+//
+// SPDX-License-Identifier: GPL-3.0-or-later
+//
+
+#ifndef INCLUDED_LIBUHD_IO_SERVICE_MGR_HPP
+#define INCLUDED_LIBUHD_IO_SERVICE_MGR_HPP
+
+#include <uhd/transport/adapter_id.hpp>
+#include <uhd/types/device_addr.hpp>
+#include <uhdlib/transport/io_service.hpp>
+#include <uhdlib/transport/link_if.hpp>
+#include <uhdlib/transport/links.hpp>
+#include <uhdlib/usrp/common/io_service_args.hpp>
+#include <memory>
+
+namespace uhd { namespace usrp {
+
+/*! Class to create and manage I/O services
+ *
+ * The I/O service manager connects links to I/O services, instantiating new I/O
+ * services as needed. It chooses the I/O service to connect based on options
+ * from the user passed through stream_args, as well as defaults provided by the
+ * caller.
+ *
+ * The I/O service manager supports two types of I/O services: inline I/O service
+ * and offload I/O service. Inline I/O services execute all I/O in the caller
+ * thread. Offload I/O services execute all I/O in an offload thread. The offload
+ * thread can be configured to block or poll. All control links use inline I/O
+ * services, only RX and TX data links currently use offload I/O services.
+ *
+ * If polling I/O services are requested, the I/O service manager instantiates
+ * the number of I/O services specified by the user through args. It chooses
+ * which I/O service to connect a set of links to by selecting the I/O service
+ * with the fewest number of connections.
+ *
+ * If blocking I/O services are requested, the I/O service manager instantiates
+ * one offload I/O service for each transport adapter used by a streamer. When
+ * there are multiple streamers, this manager creates a separate set of I/O
+ * services for each streamer.
+ *
+ * Offload I/O services have a number of restrictions that must be observed:
+ * - Offload I/O services currently do not support links that require frame
+ *   buffers to be released in order.
+ * - Blocking I/O services should only be used for groups of RX or TX data
+ *   transport in the same streamer. Since the I/O service blocks on each
+ *   channel, if two streamers were to be configured to share the I/O service,
+ *   one streamer would block the progress of the other. The I/O service
+ *   manager ensures this restriction is observed by grouping I/O services
+ *   and links appropriately.
+ * - Blocking I/O services do not currently support muxed links, since the I/O
+ *   service is specialized to either RX or TX data and the procedure to configure
+ *   a data transport requires both RX and TX clients. The I/O service manager
+ *   throws an exception if requested to mux a link configured with a blocking
+ *   I/O service.
+ */
+class io_service_mgr
+{
+public:
+    using sptr = std::shared_ptr<io_service_mgr>;
+
+    /*! Connects a pair of links to an I/O service
+     *
+     * Call this method to connect a pair of links to an I/O service. For muxed
+     * links, the I/O service manager keeps track of the number of muxed
+     * connections (the number of times this method has been called with the same
+     * links).
+     *
+     * The last two parameters are ignored for control links.
+     *
+     * \param recv_link The recv link to connect to an I/O service
+     * \param send_link The send link to connect to an I/O service
+     * \param link_type The type of transport in which the links will be used
+     * \param io_srv_args The user-requested options for the stream
+     * \param streamer_id A unique ID for the streamer that will use the links
+     * \return The I/O service to which the links are connected
+     */
+    virtual transport::io_service::sptr connect_links(
+        transport::recv_link_if::sptr recv_link,
+        transport::send_link_if::sptr send_link,
+        const transport::link_type_t link_type,
+        const io_service_args_t& io_srv_args = io_service_args_t(),
+        const std::string& streamer_id       = "") = 0;
+
+    /*! Disconnects links from their I/O service
+     *
+     * \param recv_link The recv link to disconnect from an I/O service
+     * \param send_link The send link to disconnect from an I/O service
+     */
+    virtual void disconnect_links(transport::recv_link_if::sptr recv_link,
+        transport::send_link_if::sptr send_link) = 0;
+
+    /*! Creates an instance of an I/O service manager
+     *
+     * \params Device args used to create the UHD session
+     * \return The I/O service manager instance
+     */
+    static sptr make(const uhd::device_addr_t& args);
+};
+
+}} // namespace uhd::usrp
+
+#endif /* INCLUDED_LIBUHD_IO_SERVICE_MGR_HPP */