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diff --git a/doc/guides/sample_app_ug/multi_process.rst b/doc/guides/sample_app_ug/multi_process.rst new file mode 100644 index 00000000..35714905 --- /dev/null +++ b/doc/guides/sample_app_ug/multi_process.rst @@ -0,0 +1,774 @@ +.. BSD LICENSE + Copyright(c) 2010-2014 Intel Corporation. All rights reserved. + All rights reserved. + + Redistribution and use in source and binary forms, with or without + modification, are permitted provided that the following conditions + are met: + + * Redistributions of source code must retain the above copyright + notice, this list of conditions and the following disclaimer. + * Redistributions in binary form must reproduce the above copyright + notice, this list of conditions and the following disclaimer in + the documentation and/or other materials provided with the + distribution. + * Neither the name of Intel Corporation nor the names of its + contributors may be used to endorse or promote products derived + from this software without specific prior written permission. + + THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS + "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT + LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR + A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT + OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, + SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT + LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, + DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY + THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE + OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + +.. _multi_process_app: + +Multi-process Sample Application +================================ + +This chapter describes the example applications for multi-processing that are included in the DPDK. + +Example Applications +-------------------- + +Building the Sample Applications +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The multi-process example applications are built in the same way as other sample applications, +and as documented in the *DPDK Getting Started Guide*. +To build all the example applications: + +#. Set RTE_SDK and go to the example directory: + + .. code-block:: console + + export RTE_SDK=/path/to/rte_sdk + cd ${RTE_SDK}/examples/multi_process + +#. Set the target (a default target will be used if not specified). For example: + + .. code-block:: console + + export RTE_TARGET=x86_64-native-linuxapp-gcc + + See the *DPDK Getting Started Guide* for possible RTE_TARGET values. + +#. Build the applications: + + .. code-block:: console + + make + +.. note:: + + If just a specific multi-process application needs to be built, + the final make command can be run just in that application's directory, + rather than at the top-level multi-process directory. + +Basic Multi-process Example +~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The examples/simple_mp folder in the DPDK release contains a basic example application to demonstrate how +two DPDK processes can work together using queues and memory pools to share information. + +Running the Application +^^^^^^^^^^^^^^^^^^^^^^^ + +To run the application, start one copy of the simple_mp binary in one terminal, +passing at least two cores in the coremask, as follows: + +.. code-block:: console + + ./build/simple_mp -c 3 -n 4 --proc-type=primary + +For the first DPDK process run, the proc-type flag can be omitted or set to auto, +since all DPDK processes will default to being a primary instance, +meaning they have control over the hugepage shared memory regions. +The process should start successfully and display a command prompt as follows: + +.. code-block:: console + + $ ./build/simple_mp -c 3 -n 4 --proc-type=primary + EAL: coremask set to 3 + EAL: Detected lcore 0 on socket 0 + EAL: Detected lcore 1 on socket 0 + EAL: Detected lcore 2 on socket 0 + EAL: Detected lcore 3 on socket 0 + ... + + EAL: Requesting 2 pages of size 1073741824 + EAL: Requesting 768 pages of size 2097152 + EAL: Ask a virtual area of 0x40000000 bytes + EAL: Virtual area found at 0x7ff200000000 (size = 0x40000000) + ... + + EAL: check igb_uio module + EAL: check module finished + EAL: Master core 0 is ready (tid=54e41820) + EAL: Core 1 is ready (tid=53b32700) + + Starting core 1 + + simple_mp > + +To run the secondary process to communicate with the primary process, +again run the same binary setting at least two cores in the coremask: + +.. code-block:: console + + ./build/simple_mp -c C -n 4 --proc-type=secondary + +When running a secondary process such as that shown above, the proc-type parameter can again be specified as auto. +However, omitting the parameter altogether will cause the process to try and start as a primary rather than secondary process. + +Once the process type is specified correctly, +the process starts up, displaying largely similar status messages to the primary instance as it initializes. +Once again, you will be presented with a command prompt. + +Once both processes are running, messages can be sent between them using the send command. +At any stage, either process can be terminated using the quit command. + +.. code-block:: console + + EAL: Master core 10 is ready (tid=b5f89820) EAL: Master core 8 is ready (tid=864a3820) + EAL: Core 11 is ready (tid=84ffe700) EAL: Core 9 is ready (tid=85995700) + Starting core 11 Starting core 9 + simple_mp > send hello_secondary simple_mp > core 9: Received 'hello_secondary' + simple_mp > core 11: Received 'hello_primary' simple_mp > send hello_primary + simple_mp > quit simple_mp > quit + +.. note:: + + If the primary instance is terminated, the secondary instance must also be shut-down and restarted after the primary. + This is necessary because the primary instance will clear and reset the shared memory regions on startup, + invalidating the secondary process's pointers. + The secondary process can be stopped and restarted without affecting the primary process. + +How the Application Works +^^^^^^^^^^^^^^^^^^^^^^^^^ + +The core of this example application is based on using two queues and a single memory pool in shared memory. +These three objects are created at startup by the primary process, +since the secondary process cannot create objects in memory as it cannot reserve memory zones, +and the secondary process then uses lookup functions to attach to these objects as it starts up. + +.. code-block:: c + + if (rte_eal_process_type() == RTE_PROC_PRIMARY){ + send_ring = rte_ring_create(_PRI_2_SEC, ring_size, SOCKET0, flags); + recv_ring = rte_ring_create(_SEC_2_PRI, ring_size, SOCKET0, flags); + message_pool = rte_mempool_create(_MSG_POOL, pool_size, string_size, pool_cache, priv_data_sz, NULL, NULL, NULL, NULL, SOCKET0, flags); + } else { + recv_ring = rte_ring_lookup(_PRI_2_SEC); + send_ring = rte_ring_lookup(_SEC_2_PRI); + message_pool = rte_mempool_lookup(_MSG_POOL); + } + +Note, however, that the named ring structure used as send_ring in the primary process is the recv_ring in the secondary process. + +Once the rings and memory pools are all available in both the primary and secondary processes, +the application simply dedicates two threads to sending and receiving messages respectively. +The receive thread simply dequeues any messages on the receive ring, prints them, +and frees the buffer space used by the messages back to the memory pool. +The send thread makes use of the command-prompt library to interactively request user input for messages to send. +Once a send command is issued by the user, a buffer is allocated from the memory pool, filled in with the message contents, +then enqueued on the appropriate rte_ring. + +Symmetric Multi-process Example +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The second example of DPDK multi-process support demonstrates how a set of processes can run in parallel, +with each process performing the same set of packet- processing operations. +(Since each process is identical in functionality to the others, +we refer to this as symmetric multi-processing, to differentiate it from asymmetric multi- processing - +such as a client-server mode of operation seen in the next example, +where different processes perform different tasks, yet co-operate to form a packet-processing system.) +The following diagram shows the data-flow through the application, using two processes. + +.. _figure_sym_multi_proc_app: + +.. figure:: img/sym_multi_proc_app.* + + Example Data Flow in a Symmetric Multi-process Application + + +As the diagram shows, each process reads packets from each of the network ports in use. +RSS is used to distribute incoming packets on each port to different hardware RX queues. +Each process reads a different RX queue on each port and so does not contend with any other process for that queue access. +Similarly, each process writes outgoing packets to a different TX queue on each port. + +Running the Application +^^^^^^^^^^^^^^^^^^^^^^^ + +As with the simple_mp example, the first instance of the symmetric_mp process must be run as the primary instance, +though with a number of other application- specific parameters also provided after the EAL arguments. +These additional parameters are: + +* -p <portmask>, where portmask is a hexadecimal bitmask of what ports on the system are to be used. + For example: -p 3 to use ports 0 and 1 only. + +* --num-procs <N>, where N is the total number of symmetric_mp instances that will be run side-by-side to perform packet processing. + This parameter is used to configure the appropriate number of receive queues on each network port. + +* --proc-id <n>, where n is a numeric value in the range 0 <= n < N (number of processes, specified above). + This identifies which symmetric_mp instance is being run, so that each process can read a unique receive queue on each network port. + +The secondary symmetric_mp instances must also have these parameters specified, +and the first two must be the same as those passed to the primary instance, or errors result. + +For example, to run a set of four symmetric_mp instances, running on lcores 1-4, +all performing level-2 forwarding of packets between ports 0 and 1, +the following commands can be used (assuming run as root): + +.. code-block:: console + + # ./build/symmetric_mp -c 2 -n 4 --proc-type=auto -- -p 3 --num-procs=4 --proc-id=0 + # ./build/symmetric_mp -c 4 -n 4 --proc-type=auto -- -p 3 --num-procs=4 --proc-id=1 + # ./build/symmetric_mp -c 8 -n 4 --proc-type=auto -- -p 3 --num-procs=4 --proc-id=2 + # ./build/symmetric_mp -c 10 -n 4 --proc-type=auto -- -p 3 --num-procs=4 --proc-id=3 + +.. note:: + + In the above example, the process type can be explicitly specified as primary or secondary, rather than auto. + When using auto, the first process run creates all the memory structures needed for all processes - + irrespective of whether it has a proc-id of 0, 1, 2 or 3. + +.. note:: + + For the symmetric multi-process example, since all processes work in the same manner, + once the hugepage shared memory and the network ports are initialized, + it is not necessary to restart all processes if the primary instance dies. + Instead, that process can be restarted as a secondary, + by explicitly setting the proc-type to secondary on the command line. + (All subsequent instances launched will also need this explicitly specified, + as auto-detection will detect no primary processes running and therefore attempt to re-initialize shared memory.) + +How the Application Works +^^^^^^^^^^^^^^^^^^^^^^^^^ + +The initialization calls in both the primary and secondary instances are the same for the most part, +calling the rte_eal_init(), 1 G and 10 G driver initialization and then rte_eal_pci_probe() functions. +Thereafter, the initialization done depends on whether the process is configured as a primary or secondary instance. + +In the primary instance, a memory pool is created for the packet mbufs and the network ports to be used are initialized - +the number of RX and TX queues per port being determined by the num-procs parameter passed on the command-line. +The structures for the initialized network ports are stored in shared memory and +therefore will be accessible by the secondary process as it initializes. + +.. code-block:: c + + if (num_ports & 1) + rte_exit(EXIT_FAILURE, "Application must use an even number of ports\n"); + + for(i = 0; i < num_ports; i++){ + if(proc_type == RTE_PROC_PRIMARY) + if (smp_port_init(ports[i], mp, (uint16_t)num_procs) < 0) + rte_exit(EXIT_FAILURE, "Error initializing ports\n"); + } + +In the secondary instance, rather than initializing the network ports, the port information exported by the primary process is used, +giving the secondary process access to the hardware and software rings for each network port. +Similarly, the memory pool of mbufs is accessed by doing a lookup for it by name: + +.. code-block:: c + + mp = (proc_type == RTE_PROC_SECONDARY) ? rte_mempool_lookup(_SMP_MBUF_POOL) : rte_mempool_create(_SMP_MBUF_POOL, NB_MBUFS, MBUF_SIZE, ... ) + +Once this initialization is complete, the main loop of each process, both primary and secondary, +is exactly the same - each process reads from each port using the queue corresponding to its proc-id parameter, +and writes to the corresponding transmit queue on the output port. + +Client-Server Multi-process Example +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The third example multi-process application included with the DPDK shows how one can +use a client-server type multi-process design to do packet processing. +In this example, a single server process performs the packet reception from the ports being used and +distributes these packets using round-robin ordering among a set of client processes, +which perform the actual packet processing. +In this case, the client applications just perform level-2 forwarding of packets by sending each packet out on a different network port. + +The following diagram shows the data-flow through the application, using two client processes. + +.. _figure_client_svr_sym_multi_proc_app: + +.. figure:: img/client_svr_sym_multi_proc_app.* + + Example Data Flow in a Client-Server Symmetric Multi-process Application + + +Running the Application +^^^^^^^^^^^^^^^^^^^^^^^ + +The server process must be run initially as the primary process to set up all memory structures for use by the clients. +In addition to the EAL parameters, the application- specific parameters are: + +* -p <portmask >, where portmask is a hexadecimal bitmask of what ports on the system are to be used. + For example: -p 3 to use ports 0 and 1 only. + +* -n <num-clients>, where the num-clients parameter is the number of client processes that will process the packets received + by the server application. + +.. note:: + + In the server process, a single thread, the master thread, that is, the lowest numbered lcore in the coremask, performs all packet I/O. + If a coremask is specified with more than a single lcore bit set in it, + an additional lcore will be used for a thread to periodically print packet count statistics. + +Since the server application stores configuration data in shared memory, including the network ports to be used, +the only application parameter needed by a client process is its client instance ID. +Therefore, to run a server application on lcore 1 (with lcore 2 printing statistics) along with two client processes running on lcores 3 and 4, +the following commands could be used: + +.. code-block:: console + + # ./mp_server/build/mp_server -c 6 -n 4 -- -p 3 -n 2 + # ./mp_client/build/mp_client -c 8 -n 4 --proc-type=auto -- -n 0 + # ./mp_client/build/mp_client -c 10 -n 4 --proc-type=auto -- -n 1 + +.. note:: + + If the server application dies and needs to be restarted, all client applications also need to be restarted, + as there is no support in the server application for it to run as a secondary process. + Any client processes that need restarting can be restarted without affecting the server process. + +How the Application Works +^^^^^^^^^^^^^^^^^^^^^^^^^ + +The server process performs the network port and data structure initialization much as the symmetric multi-process application does when run as primary. +One additional enhancement in this sample application is that the server process stores its port configuration data in a memory zone in hugepage shared memory. +This eliminates the need for the client processes to have the portmask parameter passed into them on the command line, +as is done for the symmetric multi-process application, and therefore eliminates mismatched parameters as a potential source of errors. + +In the same way that the server process is designed to be run as a primary process instance only, +the client processes are designed to be run as secondary instances only. +They have no code to attempt to create shared memory objects. +Instead, handles to all needed rings and memory pools are obtained via calls to rte_ring_lookup() and rte_mempool_lookup(). +The network ports for use by the processes are obtained by loading the network port drivers and probing the PCI bus, +which will, as in the symmetric multi-process example, +automatically get access to the network ports using the settings already configured by the primary/server process. + +Once all applications are initialized, the server operates by reading packets from each network port in turn and +distributing those packets to the client queues (software rings, one for each client process) in round-robin order. +On the client side, the packets are read from the rings in as big of bursts as possible, then routed out to a different network port. +The routing used is very simple. All packets received on the first NIC port are transmitted back out on the second port and vice versa. +Similarly, packets are routed between the 3rd and 4th network ports and so on. +The sending of packets is done by writing the packets directly to the network ports; they are not transferred back via the server process. + +In both the server and the client processes, outgoing packets are buffered before being sent, +so as to allow the sending of multiple packets in a single burst to improve efficiency. +For example, the client process will buffer packets to send, +until either the buffer is full or until we receive no further packets from the server. + +Master-slave Multi-process Example +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The fourth example of DPDK multi-process support demonstrates a master-slave model that +provide the capability of application recovery if a slave process crashes or meets unexpected conditions. +In addition, it also demonstrates the floating process, +which can run among different cores in contrast to the traditional way of binding a process/thread to a specific CPU core, +using the local cache mechanism of mempool structures. + +This application performs the same functionality as the L2 Forwarding sample application, +therefore this chapter does not cover that part but describes functionality that is introduced in this multi-process example only. +Please refer to :doc:`l2_forward_real_virtual` for more information. + +Unlike previous examples where all processes are started from the command line with input arguments, in this example, +only one process is spawned from the command line and that process creates other processes. +The following section describes this in more detail. + +Master-slave Process Models +^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +The process spawned from the command line is called the *master process* in this document. +A process created by the master is called a *slave process*. +The application has only one master process, but could have multiple slave processes. + +Once the master process begins to run, it tries to initialize all the resources such as +memory, CPU cores, driver, ports, and so on, as the other examples do. +Thereafter, it creates slave processes, as shown in the following figure. + +.. _figure_master_slave_proc: + +.. figure:: img/master_slave_proc.* + + Master-slave Process Workflow + + +The master process calls the rte_eal_mp_remote_launch() EAL function to launch an application function for each pinned thread through the pipe. +Then, it waits to check if any slave processes have exited. +If so, the process tries to re-initialize the resources that belong to that slave and launch them in the pinned thread entry again. +The following section describes the recovery procedures in more detail. + +For each pinned thread in EAL, after reading any data from the pipe, it tries to call the function that the application specified. +In this master specified function, a fork() call creates a slave process that performs the L2 forwarding task. +Then, the function waits until the slave exits, is killed or crashes. Thereafter, it notifies the master of this event and returns. +Finally, the EAL pinned thread waits until the new function is launched. + +After discussing the master-slave model, it is necessary to mention another issue, global and static variables. + +For multiple-thread cases, all global and static variables have only one copy and they can be accessed by any thread if applicable. +So, they can be used to sync or share data among threads. + +In the previous examples, each process has separate global and static variables in memory and are independent of each other. +If it is necessary to share the knowledge, some communication mechanism should be deployed, such as, memzone, ring, shared memory, and so on. +The global or static variables are not a valid approach to share data among processes. +For variables in this example, on the one hand, the slave process inherits all the knowledge of these variables after being created by the master. +On the other hand, other processes cannot know if one or more processes modifies them after slave creation since that +is the nature of a multiple process address space. +But this does not mean that these variables cannot be used to share or sync data; it depends on the use case. +The following are the possible use cases: + +#. The master process starts and initializes a variable and it will never be changed after slave processes created. This case is OK. + +#. After the slave processes are created, the master or slave cores need to change a variable, but other processes do not need to know the change. + This case is also OK. + +#. After the slave processes are created, the master or a slave needs to change a variable. + In the meantime, one or more other process needs to be aware of the change. + In this case, global and static variables cannot be used to share knowledge. Another communication mechanism is needed. + A simple approach without lock protection can be a heap buffer allocated by rte_malloc or mem zone. + +Slave Process Recovery Mechanism +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +Before talking about the recovery mechanism, it is necessary to know what is needed before a new slave instance can run if a previous one exited. + +When a slave process exits, the system returns all the resources allocated for this process automatically. +However, this does not include the resources that were allocated by the DPDK. All the hardware resources are shared among the processes, +which include memzone, mempool, ring, a heap buffer allocated by the rte_malloc library, and so on. +If the new instance runs and the allocated resource is not returned, either resource allocation failed or the hardware resource is lost forever. + +When a slave process runs, it may have dependencies on other processes. +They could have execution sequence orders; they could share the ring to communicate; they could share the same port for reception and forwarding; +they could use lock structures to do exclusive access in some critical path. +What happens to the dependent process(es) if the peer leaves? +The consequence are varied since the dependency cases are complex. +It depends on what the processed had shared. +However, it is necessary to notify the peer(s) if one slave exited. +Then, the peer(s) will be aware of that and wait until the new instance begins to run. + +Therefore, to provide the capability to resume the new slave instance if the previous one exited, it is necessary to provide several mechanisms: + +#. Keep a resource list for each slave process. + Before a slave process run, the master should prepare a resource list. + After it exits, the master could either delete the allocated resources and create new ones, + or re-initialize those for use by the new instance. + +#. Set up a notification mechanism for slave process exit cases. After the specific slave leaves, + the master should be notified and then help to create a new instance. + This mechanism is provided in Section `Master-slave Process Models`_. + +#. Use a synchronization mechanism among dependent processes. + The master should have the capability to stop or kill slave processes that have a dependency on the one that has exited. + Then, after the new instance of exited slave process begins to run, the dependency ones could resume or run from the start. + The example sends a STOP command to slave processes dependent on the exited one, then they will exit. + Thereafter, the master creates new instances for the exited slave processes. + +The following diagram describes slave process recovery. + +.. _figure_slave_proc_recov: + +.. figure:: img/slave_proc_recov.* + + Slave Process Recovery Process Flow + + +Floating Process Support +^^^^^^^^^^^^^^^^^^^^^^^^ + +When the DPDK application runs, there is always a -c option passed in to indicate the cores that are enabled. +Then, the DPDK creates a thread for each enabled core. +By doing so, it creates a 1:1 mapping between the enabled core and each thread. +The enabled core always has an ID, therefore, each thread has a unique core ID in the DPDK execution environment. +With the ID, each thread can easily access the structures or resources exclusively belonging to it without using function parameter passing. +It can easily use the rte_lcore_id() function to get the value in every function that is called. + +For threads/processes not created in that way, either pinned to a core or not, they will not own a unique ID and the +rte_lcore_id() function will not work in the correct way. +However, sometimes these threads/processes still need the unique ID mechanism to do easy access on structures or resources. +For example, the DPDK mempool library provides a local cache mechanism +(refer to :ref:`mempool_local_cache`) +for fast element allocation and freeing. +If using a non-unique ID or a fake one, +a race condition occurs if two or more threads/ processes with the same core ID try to use the local cache. + +Therefore, unused core IDs from the passing of parameters with the -c option are used to organize the core ID allocation array. +Once the floating process is spawned, it tries to allocate a unique core ID from the array and release it on exit. + +A natural way to spawn a floating process is to use the fork() function and allocate a unique core ID from the unused core ID array. +However, it is necessary to write new code to provide a notification mechanism for slave exit +and make sure the process recovery mechanism can work with it. + +To avoid producing redundant code, the Master-Slave process model is still used to spawn floating processes, +then cancel the affinity to specific cores. +Besides that, clear the core ID assigned to the DPDK spawning a thread that has a 1:1 mapping with the core mask. +Thereafter, get a new core ID from the unused core ID allocation array. + +Run the Application +^^^^^^^^^^^^^^^^^^^ + +This example has a command line similar to the L2 Forwarding sample application with a few differences. + +To run the application, start one copy of the l2fwd_fork binary in one terminal. +Unlike the L2 Forwarding example, +this example requires at least three cores since the master process will wait and be accountable for slave process recovery. +The command is as follows: + +.. code-block:: console + + #./build/l2fwd_fork -c 1c -n 4 -- -p 3 -f + +This example provides another -f option to specify the use of floating process. +If not specified, the example will use a pinned process to perform the L2 forwarding task. + +To verify the recovery mechanism, proceed as follows: First, check the PID of the slave processes: + +.. code-block:: console + + #ps -fe | grep l2fwd_fork + root 5136 4843 29 11:11 pts/1 00:00:05 ./build/l2fwd_fork + root 5145 5136 98 11:11 pts/1 00:00:11 ./build/l2fwd_fork + root 5146 5136 98 11:11 pts/1 00:00:11 ./build/l2fwd_fork + +Then, kill one of the slaves: + +.. code-block:: console + + #kill -9 5145 + +After 1 or 2 seconds, check whether the slave has resumed: + +.. code-block:: console + + #ps -fe | grep l2fwd_fork + root 5136 4843 3 11:11 pts/1 00:00:06 ./build/l2fwd_fork + root 5247 5136 99 11:14 pts/1 00:00:01 ./build/l2fwd_fork + root 5248 5136 99 11:14 pts/1 00:00:01 ./build/l2fwd_fork + +It can also monitor the traffic generator statics to see whether slave processes have resumed. + +Explanation +^^^^^^^^^^^ + +As described in previous sections, +not all global and static variables need to change to be accessible in multiple processes; +it depends on how they are used. +In this example, +the statics info on packets dropped/forwarded/received count needs to be updated by the slave process, +and the master needs to see the update and print them out. +So, it needs to allocate a heap buffer using rte_zmalloc. +In addition, if the -f option is specified, +an array is needed to store the allocated core ID for the floating process so that the master can return it +after a slave has exited accidentally. + +.. code-block:: c + + static int + l2fwd_malloc_shared_struct(void) + { + port_statistics = rte_zmalloc("port_stat", sizeof(struct l2fwd_port_statistics) * RTE_MAX_ETHPORTS, 0); + + if (port_statistics == NULL) + return -1; + + /* allocate mapping_id array */ + + if (float_proc) { + int i; + + mapping_id = rte_malloc("mapping_id", sizeof(unsigned) * RTE_MAX_LCORE, 0); + if (mapping_id == NULL) + return -1; + + for (i = 0 ;i < RTE_MAX_LCORE; i++) + mapping_id[i] = INVALID_MAPPING_ID; + + } + return 0; + } + +For each slave process, packets are received from one port and forwarded to another port that another slave is operating on. +If the other slave exits accidentally, the port it is operating on may not work normally, +so the first slave cannot forward packets to that port. +There is a dependency on the port in this case. So, the master should recognize the dependency. +The following is the code to detect this dependency: + +.. code-block:: c + + for (portid = 0; portid < nb_ports; portid++) { + /* skip ports that are not enabled */ + + if ((l2fwd_enabled_port_mask & (1 << portid)) == 0) + continue; + + /* Find pair ports' lcores */ + + find_lcore = find_pair_lcore = 0; + pair_port = l2fwd_dst_ports[portid]; + + for (i = 0; i < RTE_MAX_LCORE; i++) { + if (!rte_lcore_is_enabled(i)) + continue; + + for (j = 0; j < lcore_queue_conf[i].n_rx_port;j++) { + if (lcore_queue_conf[i].rx_port_list[j] == portid) { + lcore = i; + find_lcore = 1; + break; + } + + if (lcore_queue_conf[i].rx_port_list[j] == pair_port) { + pair_lcore = i; + find_pair_lcore = 1; + break; + } + } + + if (find_lcore && find_pair_lcore) + break; + } + + if (!find_lcore || !find_pair_lcore) + rte_exit(EXIT_FAILURE, "Not find port=%d pair\\n", portid); + + printf("lcore %u and %u paired\\n", lcore, pair_lcore); + + lcore_resource[lcore].pair_id = pair_lcore; + lcore_resource[pair_lcore].pair_id = lcore; + } + +Before launching the slave process, +it is necessary to set up the communication channel between the master and slave so that +the master can notify the slave if its peer process with the dependency exited. +In addition, the master needs to register a callback function in the case where a specific slave exited. + +.. code-block:: c + + for (i = 0; i < RTE_MAX_LCORE; i++) { + if (lcore_resource[i].enabled) { + /* Create ring for master and slave communication */ + + ret = create_ms_ring(i); + if (ret != 0) + rte_exit(EXIT_FAILURE, "Create ring for lcore=%u failed",i); + + if (flib_register_slave_exit_notify(i,slave_exit_cb) != 0) + rte_exit(EXIT_FAILURE, "Register master_trace_slave_exit failed"); + } + } + +After launching the slave process, the master waits and prints out the port statics periodically. +If an event indicating that a slave process exited is detected, +it sends the STOP command to the peer and waits until it has also exited. +Then, it tries to clean up the execution environment and prepare new resources. +Finally, the new slave instance is launched. + +.. code-block:: c + + while (1) { + sleep(1); + cur_tsc = rte_rdtsc(); + diff_tsc = cur_tsc - prev_tsc; + + /* if timer is enabled */ + + if (timer_period > 0) { + /* advance the timer */ + timer_tsc += diff_tsc; + + /* if timer has reached its timeout */ + if (unlikely(timer_tsc >= (uint64_t) timer_period)) { + print_stats(); + + /* reset the timer */ + timer_tsc = 0; + } + } + + prev_tsc = cur_tsc; + + /* Check any slave need restart or recreate */ + + rte_spinlock_lock(&res_lock); + + for (i = 0; i < RTE_MAX_LCORE; i++) { + struct lcore_resource_struct *res = &lcore_resource[i]; + struct lcore_resource_struct *pair = &lcore_resource[res->pair_id]; + + /* If find slave exited, try to reset pair */ + + if (res->enabled && res->flags && pair->enabled) { + if (!pair->flags) { + master_sendcmd_with_ack(pair->lcore_id, CMD_STOP); + rte_spinlock_unlock(&res_lock); + sleep(1); + rte_spinlock_lock(&res_lock); + if (pair->flags) + continue; + } + + if (reset_pair(res->lcore_id, pair->lcore_id) != 0) + rte_exit(EXIT_FAILURE, "failed to reset slave"); + + res->flags = 0; + pair->flags = 0; + } + } + rte_spinlock_unlock(&res_lock); + } + +When the slave process is spawned and starts to run, it checks whether the floating process option is applied. +If so, it clears the affinity to a specific core and also sets the unique core ID to 0. +Then, it tries to allocate a new core ID. +Since the core ID has changed, the resource allocated by the master cannot work, +so it remaps the resource to the new core ID slot. + +.. code-block:: c + + static int + l2fwd_launch_one_lcore( attribute ((unused)) void *dummy) + { + unsigned lcore_id = rte_lcore_id(); + + if (float_proc) { + unsigned flcore_id; + + /* Change it to floating process, also change it's lcore_id */ + + clear_cpu_affinity(); + + RTE_PER_LCORE(_lcore_id) = 0; + + /* Get a lcore_id */ + + if (flib_assign_lcore_id() < 0 ) { + printf("flib_assign_lcore_id failed\n"); + return -1; + } + + flcore_id = rte_lcore_id(); + + /* Set mapping id, so master can return it after slave exited */ + + mapping_id[lcore_id] = flcore_id; + printf("Org lcore_id = %u, cur lcore_id = %u\n",lcore_id, flcore_id); + remapping_slave_resource(lcore_id, flcore_id); + } + + l2fwd_main_loop(); + + /* return lcore_id before return */ + if (float_proc) { + flib_free_lcore_id(rte_lcore_id()); + mapping_id[lcore_id] = INVALID_MAPPING_ID; + } + return 0; + } |