ceph/src/spdk/dpdk/doc/guides/cryptodevs/scheduler.rst

   1 ..  SPDX-License-Identifier: BSD-3-Clause
   2     Copyright(c) 2017 Intel Corporation.
   3
   4 Cryptodev Scheduler Poll Mode Driver Library
   5 ============================================
   6
   7 Scheduler PMD is a software crypto PMD, which has the capabilities of
   8 attaching hardware and/or software cryptodevs, and distributes ingress
   9 crypto ops among them in a certain manner.
  10
  11 .. figure:: img/scheduler-overview.*
  12
  13    Cryptodev Scheduler Overview
  14
  15
  16 The Cryptodev Scheduler PMD library (**librte_pmd_crypto_scheduler**) acts as
  17 a software crypto PMD and shares the same API provided by librte_cryptodev.
  18 The PMD supports attaching multiple crypto PMDs, software or hardware, as
  19 slaves, and distributes the crypto workload to them with certain behavior.
  20 The behaviors are categorizes as different "modes". Basically, a scheduling
  21 mode defines certain actions for scheduling crypto ops to its slaves.
  22
  23 The librte_pmd_crypto_scheduler library exports a C API which provides an API
  24 for attaching/detaching slaves, set/get scheduling modes, and enable/disable
  25 crypto ops reordering.
  26
  27 Limitations
  28 -----------
  29
  30 * Sessionless crypto operation is not supported
  31 * OOP crypto operation is not supported when the crypto op reordering feature
  32   is enabled.
  33
  34
  35 Installation
  36 ------------
  37
  38 To build DPDK with CRYTPO_SCHEDULER_PMD the user is required to set
  39 CONFIG_RTE_LIBRTE_PMD_CRYPTO_SCHEDULER=y in config/common_base, and
  40 recompile DPDK
  41
  42
  43 Initialization
  44 --------------
  45
  46 To use the PMD in an application, user must:
  47
  48 * Call rte_vdev_init("crypto_scheduler") within the application.
  49
  50 * Use --vdev="crypto_scheduler" in the EAL options, which will call
  51   rte_vdev_init() internally.
  52
  53
  54 The following parameters (all optional) can be provided in the previous
  55 two calls:
  56
  57 * socket_id: Specify the socket where the memory for the device is going
  58   to be allocated (by default, socket_id will be the socket where the core
  59   that is creating the PMD is running on).
  60
  61 * max_nb_sessions: Specify the maximum number of sessions that can be
  62   created. This value may be overwritten internally if there are too
  63   many devices are attached.
  64
  65 * slave: If a cryptodev has been initialized with specific name, it can be
  66   attached to the scheduler using this parameter, simply filling the name
  67   here. Multiple cryptodevs can be attached initially by presenting this
  68   parameter multiple times.
  69
  70 * mode: Specify the scheduling mode of the PMD. The supported scheduling
  71   mode parameter values are specified in the "Cryptodev Scheduler Modes
  72   Overview" section.
  73
  74 * mode_param: Specify the mode-specific parameter. Some scheduling modes
  75   may be initialized with specific parameters other than the default ones,
  76   such as the **threshold** packet size of **packet-size-distr** mode. This
  77   parameter fulfills the purpose.
  78
  79 * ordering: Specify the status of the crypto operations ordering feature.
  80   The value of this parameter can be "enable" or "disable". This feature
  81   is disabled by default.
  82
  83 Example:
  84
  85 .. code-block:: console
  86
  87     ... --vdev "crypto_aesni_mb0,name=aesni_mb_1" --vdev "crypto_aesni_mb1,name=aesni_mb_2" --vdev "crypto_scheduler,slave=aesni_mb_1,slave=aesni_mb_2" ...
  88
  89 .. note::
  90
  91     * The scheduler cryptodev cannot be started unless the scheduling mode
  92       is set and at least one slave is attached. Also, to configure the
  93       scheduler in the run-time, like attach/detach slave(s), change
  94       scheduling mode, or enable/disable crypto op ordering, one should stop
  95       the scheduler first, otherwise an error will be returned.
  96
  97     * The crypto op reordering feature requires using the userdata field of
  98       every mbuf to be processed to store temporary data. By the end of
  99       processing, the field is set to pointing to NULL, any previously
 100       stored value of this field will be lost.
 101
 102
 103 Cryptodev Scheduler Modes Overview
 104 ----------------------------------
 105
 106 Currently the Crypto Scheduler PMD library supports following modes of
 107 operation:
 108
 109 *   **CDEV_SCHED_MODE_ROUNDROBIN:**
 110
 111    *Initialization mode parameter*: **round-robin**
 112
 113    Round-robin mode, which distributes the enqueued burst of crypto ops
 114    among its slaves in a round-robin manner. This mode may help to fill
 115    the throughput gap between the physical core and the existing cryptodevs
 116    to increase the overall performance.
 117
 118 *   **CDEV_SCHED_MODE_PKT_SIZE_DISTR:**
 119
 120    *Initialization mode parameter*: **packet-size-distr**
 121
 122    Packet-size based distribution mode, which works with 2 slaves, the primary
 123    slave and the secondary slave, and distributes the enqueued crypto
 124    operations to them based on their data lengths. A crypto operation will be
 125    distributed to the primary slave if its data length is equal to or bigger
 126    than the designated threshold, otherwise it will be handled by the secondary
 127    slave.
 128
 129    A typical usecase in this mode is with the QAT cryptodev as the primary and
 130    a software cryptodev as the secondary slave. This may help applications to
 131    process additional crypto workload than what the QAT cryptodev can handle on
 132    its own, by making use of the available CPU cycles to deal with smaller
 133    crypto workloads.
 134
 135    The threshold is set to 128 bytes by default. It can be updated by calling
 136    function **rte_cryptodev_scheduler_option_set**. The parameter of
 137    **option_type** must be **CDEV_SCHED_OPTION_THRESHOLD** and **option** should
 138    point to a rte_cryptodev_scheduler_threshold_option structure filled with
 139    appropriate threshold value. Please NOTE this threshold has be a power-of-2
 140    unsigned integer. It is possible to use **mode_param** initialization
 141    parameter to achieve the same purpose. For example:
 142
 143    ... --vdev "crypto_scheduler,mode=packet-size-distr,mode_param=threshold:512" ...
 144
 145    The above parameter will overwrite the threshold value to 512.
 146
 147 *   **CDEV_SCHED_MODE_FAILOVER:**
 148
 149    *Initialization mode parameter*: **fail-over**
 150
 151    Fail-over mode, which works with 2 slaves, the primary slave and the
 152    secondary slave. In this mode, the scheduler will enqueue the incoming
 153    crypto operation burst to the primary slave. When one or more crypto
 154    operations fail to be enqueued, then they will be enqueued to the secondary
 155    slave.
 156
 157 *   **CDEV_SCHED_MODE_MULTICORE:**
 158
 159    *Initialization mode parameter*: **multi-core**
 160
 161    Multi-core mode, which distributes the workload with several (up to eight)
 162    worker cores. The enqueued bursts are distributed among the worker cores in a
 163    round-robin manner. If scheduler cannot enqueue entire burst to the same worker,
 164    it will enqueue the remaining operations to the next available worker.
 165    For pure small packet size (64 bytes) traffic however the multi-core mode is not
 166    an optimal solution, as it doesn't give significant per-core performance improvement.
 167    For mixed traffic (IMIX) the optimal number of worker cores is around 2-3.
 168    For large packets (1.5 kbytes) scheduler shows linear scaling in performance
 169    up to eight cores.
 170    Each worker uses its own slave cryptodev. Only software cryptodevs
 171    are supported. Only the same type of cryptodevs should be used concurrently.
 172
 173    The multi-core mode uses one extra parameter:
 174
 175    * corelist: Semicolon-separated list of logical cores to be used as workers.
 176      The number of worker cores should be equal to the number of slave cryptodevs.
 177      These cores should be present in EAL core list parameter and
 178      should not be used by the application or any other process.
 179
 180    Example:
 181     ... --vdev "crypto_aesni_mb1,name=aesni_mb_1" --vdev "crypto_aesni_mb_pmd2,name=aesni_mb_2" \
 182     --vdev "crypto_scheduler,slave=aesni_mb_1,slave=aesni_mb_2,mode=multi-core,corelist=23;24" ...