[ovs-dev] [PATCH v1] dpdk: Support both shared and per port mempools.

Aaron Conole aconole at redhat.com
Tue Jun 26 20:30:45 UTC 2018


Hi Ian,

Ian Stokes <ian.stokes at intel.com> writes:

> This commit re-introduces the concept of shared mempools as the default
> memory model for DPDK devices. Per port mempools are still available but
> must be enabled explicitly by a user.
>
> OVS previously used a shared mempool model for ports with the same MTU
> and socket configuration. This was replaced by a per port mempool model
> to address issues flagged by users such as:
>
> https://mail.openvswitch.org/pipermail/ovs-discuss/2016-September/042560.html
>
> However the per port model potentially requires an increase in memory
> resource requirements to support the same number of ports and configuration
> as the shared port model.
>
> This is considered a blocking factor for current deployments of OVS
> when upgrading to future OVS releases as a user may have to redimension
> memory for the same deployment configuration. This may not be possible for
> users.
>
> This commit resolves the issue by re-introducing shared mempools as
> the default memory behaviour in OVS DPDK but also refactors the memory
> configuration code to allow for per port mempools.
>
> This patch adds a new global config option, per-port-memory, that
> controls the enablement of per port mempools for DPDK devices.
>
>     ovs-vsctl set Open_vSwitch . other_config:per-port-memory=true
>
> This value defaults to false; to enable per port memory support,
> this field should be set to true when setting other global parameters
> on init (such as "dpdk-socket-mem", for example). Changing the value at
> runtime is not supported, and requires restarting the vswitch
> daemon.
>
> The mempool sweep functionality is also replaced with the
> sweep functionality from OVS 2.9 found in commits
>
> c77f692 (netdev-dpdk: Free mempool only when no in-use mbufs.)
> a7fb0a4 (netdev-dpdk: Add mempool reuse/free debug.)
>
> A new document to discuss the specifics of the memory models and example
> memory requirement calculations is also added.
>
> Signed-off-by: Ian Stokes <ian.stokes at intel.com>
> ---
>  Documentation/automake.mk            |   1 +
>  Documentation/intro/install/dpdk.rst |   6 +
>  Documentation/topics/dpdk/index.rst  |   1 +
>  Documentation/topics/dpdk/memory.rst | 216 +++++++++++++++++++++++++
>  NEWS                                 |   1 +
>  lib/dpdk-stub.c                      |   6 +
>  lib/dpdk.c                           |  12 ++
>  lib/dpdk.h                           |   1 +
>  lib/netdev-dpdk.c                    | 296 +++++++++++++++++++++++------------
>  vswitchd/vswitch.xml                 |  17 ++
>  10 files changed, 457 insertions(+), 100 deletions(-)
>  create mode 100644 Documentation/topics/dpdk/memory.rst
>
> diff --git a/Documentation/automake.mk b/Documentation/automake.mk
> index bc728df..2444794 100644
> --- a/Documentation/automake.mk
> +++ b/Documentation/automake.mk
> @@ -36,6 +36,7 @@ DOC_SOURCE = \
>  	Documentation/topics/dpdk/index.rst \
>  	Documentation/topics/dpdk/bridge.rst \
>  	Documentation/topics/dpdk/jumbo-frames.rst \
> +	Documentation/topics/dpdk/memory.rst \
>  	Documentation/topics/dpdk/pdump.rst \
>  	Documentation/topics/dpdk/phy.rst \
>  	Documentation/topics/dpdk/pmd.rst \
> diff --git a/Documentation/intro/install/dpdk.rst b/Documentation/intro/install/dpdk.rst
> index 085e479..7dc75ef 100644
> --- a/Documentation/intro/install/dpdk.rst
> +++ b/Documentation/intro/install/dpdk.rst
> @@ -170,6 +170,12 @@ Mount the hugepages, if not already mounted by default::
>  
>      $ mount -t hugetlbfs none /dev/hugepages``
>  
> +.. note::
> +
> +   The amount of hugepage memory required can be affected by various
> +   aspects of the datapath and device configuration. Refer to
> +   :doc:`/topics/dpdk/memory` for more details.
> +
>  .. _dpdk-vfio:
>  
>  Setup DPDK devices using VFIO
> diff --git a/Documentation/topics/dpdk/index.rst b/Documentation/topics/dpdk/index.rst
> index 181f61a..cf24a7b 100644
> --- a/Documentation/topics/dpdk/index.rst
> +++ b/Documentation/topics/dpdk/index.rst
> @@ -40,3 +40,4 @@ The DPDK Datapath
>     /topics/dpdk/qos
>     /topics/dpdk/pdump
>     /topics/dpdk/jumbo-frames
> +   /topics/dpdk/memory
> diff --git a/Documentation/topics/dpdk/memory.rst b/Documentation/topics/dpdk/memory.rst
> new file mode 100644
> index 0000000..2e0b3f5
> --- /dev/null
> +++ b/Documentation/topics/dpdk/memory.rst
> @@ -0,0 +1,216 @@
> +..
> +      Copyright (c) 2018 Intel Corporation
> +
> +      Licensed under the Apache License, Version 2.0 (the "License"); you may
> +      not use this file except in compliance with the License. You may obtain
> +      a copy of the License at
> +
> +          http://www.apache.org/licenses/LICENSE-2.0
> +
> +      Unless required by applicable law or agreed to in writing, software
> +      distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
> +      WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
> +      License for the specific language governing permissions and limitations
> +      under the License.
> +
> +      Convention for heading levels in Open vSwitch documentation:
> +
> +      =======  Heading 0 (reserved for the title in a document)
> +      -------  Heading 1
> +      ~~~~~~~  Heading 2
> +      +++++++  Heading 3
> +      '''''''  Heading 4
> +
> +      Avoid deeper levels because they do not render well.
> +
> +=========================
> +DPDK Device Memory Models
> +=========================
> +
> +DPDK device memory can be allocated in one of two ways in OVS DPDK,
> +**shared memory** or **per port memory**. The specifics of both are
> +detailed below.
> +
> +Shared Memory
> +-------------
> +
> +By default OVS DPDK uses a shared memory model. This means that multiple
> +ports can share the same mempool. For example when a port is added it will
> +have a given MTU and socket ID associated with it. If a mempool has been
> +created previously for an existing port that has the same MTU and socket ID,
> +that mempool is used for both ports. If there is no existing mempool
> +supporting these parameters then a new mempool is created.
> +
> +Per Port Memory
> +---------------
> +
> +In the per port memory model, mempools are created per device and are not
> +shared. The benefit of this is a more transparent memory model where mempools
> +will not be exhausted by other DPDK devices. However this comes at a potential
> +increase in cost for memory dimensioning for a given deployment. Users should
> +be aware of the memory requirements for their deployment before using this
> +model and allocate the required hugepage memory.
> +
> +Per port mempool support may be enabled via a global config value,
> +```per-port-memory```. Setting this to true enables the per port memory
> +model for all DPDK devices in OVS::
> +
> +   $ ovs-vsctl set Open_vSwitch . other_config:per-port-memory=true
> +
> +.. important::
> +
> +    This value should be set before setting dpdk-init=true. If set after
> +    dpdk-init=true then the daemon must be restarted to use per-port-memory.
> +
> +Calculating Memory Requirements
> +-------------------------------
> +
> +The amount of memory required for a given mempool can be calculated by the
> +**number mbufs in the mempool \* mbuf size**.
> +
> +Users should be aware of the following:
> +
> +* The **number of mbufs** per mempool will differ between memory models.
> +
> +* The **size of each mbuf** will be affected by the requested **MTU** size.
> +
> +.. important::
> +
> +   An mbuf size in bytes can be larger than the requested MTU size due to
> +   allignment and rounding needed in OVS DPDK.
> +
> +Below are a number of examples of memory requirement calculations for both
> +shared and per port memory models.
> +
> +Shared Memory Calculations
> +~~~~~~~~~~~~~~~~~~~~~~~~~~
> +
> +In the shared memory model the number of mbufs requested is directly
> +affected by the requested MTU size as described in the table below.
> +
> ++--------------------+-------------+
> +|      MTU Size      |  Num MBUFS  |
> ++====================+=============+
> +| 1500 or greater    |   262144    |
> ++--------------------+-------------+
> +| Less than 1500     |   16384     |
> ++------------+-------+-------------+
> +
> +.. Important::
> +
> +   If a deployment does not have enough memory to provide 262144 mbufs then
> +   the requested amount is halved up until 16384.
> +
> +Example 1
> ++++++++++
> +::
> +
> + MTU = 1500 Bytes
> + Number of mbufs = 262144
> + Mbuf size = 3008 Bytes
> + Memory required = 262144 * 3008 = 788 MB
> +
> +Example 2
> ++++++++++
> +::
> +
> + MTU = 1800 Bytes
> + Number of mbufs = 262144
> + Mbuf size = 3008 Bytes
> + Memory required = 262144 * 3008 = 788 MB
> +
> +.. note::
> +
> +   Assuming the same socket is in use for example 1 and 2 the same mempool
> +   would be shared.
> +
> +Example 3
> ++++++++++
> +::
> +
> + MTU = 6000 Bytes
> + Number of mbufs = 262144
> + Mbuf size = 8128 Bytes
> + Memory required = 262144 * 8128 = 2130 MB
> +
> +Example 4
> ++++++++++
> +::
> +
> + MTU = 9000 Bytes
> + Number of mbufs = 262144
> + Mbuf size = 10176 Bytes
> + Memory required = 262144 * 10176 = 2667 MB
> +
> +Per Port Memory Calculations
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +
> +The number of mbufs requested in the per port model is more complicated and
> +accounts for multiple dynamic factors in the datapath and device
> +configuration.
> +
> +A rough estimation of the number of mbufs required for a port is:
> +::
> +
> + packets required to fill the device rxqs +
> + packets that could be stuck on other ports txqs +
> + packets on the pmd threads +
> + additional corner case memory.
> +
> +The algorithm in OVS used to calculate this is as follows:
> +::
> +
> + requested number of rxqs * requested rxq size +
> + requested number of txqs * requested txq size +
> + min(RTE_MAX_LCORE, requested number of rxqs) * netdev_max_burst +
> + MIN_NB_MBUF.
> +
> +where:
> +
> +* **requested number of rxqs**: Number of requested receive queues for a
> +  device.
> +* **requested rxq size**: The number of descriptors requested for a rx queue.
> +* **requested number of txqs**: Number of requested transmit queues for a
> +  device. Calculated as the number of PMDs configured +1.
> +* **requested txq size**: the number of descriptors requested for a tx queue.
> +* **min(RTE_MAX_LCORE,  requested number of rxqs)**: Compare the maximum
> +  number of lcores supported by DPDK to the number of requested receive
> +  queues for the device and use the variable of lesser value.
> +* **NETDEV_MAX_BURST**: Maximum number of of packets in a burst, defined as
> +  32.
> +* **MIN_NB_MBUF**: Additional memory for corner case, defined as 16384.
> +
> +For all examples below assume the following values:
> +
> +* requested_rxq_size = 2048
> +* requested_txq_size = 2048
> +* RTE_MAX_LCORE = 128
> +* netdev_max_burst = 32
> +* MIN_NB_MBUF = 16384
> +
> +Example 1: (1 rxq, 1 PMD, 1500 MTU)
> ++++++++++++++++++++++++++++++++++++
> +::
> +
> + MTU = 1500
> + Number of mbufs = (1 * 2048) + (2 * 2048) + (1 * 32) + (16384) = 22560
> + Mbuf size = 3008 Bytes
> + Memory required = 22560 * 3008 = 67 MB
> +
> +Example 2: (1 rxq, 2 PMD, 6000 MTU)
> ++++++++++++++++++++++++++++++++++++
> +::
> +
> + MTU = 6000
> + Number of mbufs = (1 * 2048) + (3 * 2048) + (1 * 32) + (16384) = 24608
> + Mbuf size = 8128 Bytes
> + Memory required = 24608 * 8128 = 200 MB
> +
> +Example 3: (2 rxq, 2 PMD, 9000 MTU)
> ++++++++++++++++++++++++++++++++++++
> +::
> +
> + MTU = 9000
> + Number of mbufs = (2 * 2048) + (3 * 2048) + (1 * 32) + (16384) = 26656
> + Mbuf size = 10176 Bytes
> + Memory required = 26656 * 10176 = 271 MB
> diff --git a/NEWS b/NEWS
> index cd15a33..8428b44 100644
> --- a/NEWS
> +++ b/NEWS
> @@ -34,6 +34,7 @@ Post-v2.9.0
>         See Testing topic for the details.
>       * Add LSC interrupt support for DPDK physical devices.
>       * Allow init to fail and record DPDK status/version in OVS database.
> +     * Support both shared and per port mempools for DPDK devices.
>     - Userspace datapath:
>       * Commands ovs-appctl dpif-netdev/pmd-*-show can now work on a single PMD
>       * Detailed PMD performance metrics available with new command
> diff --git a/lib/dpdk-stub.c b/lib/dpdk-stub.c
> index 1df1c58..1e0f461 100644
> --- a/lib/dpdk-stub.c
> +++ b/lib/dpdk-stub.c
> @@ -56,6 +56,12 @@ dpdk_vhost_iommu_enabled(void)
>      return false;
>  }
>  
> +bool
> +dpdk_per_port_memory(void)
> +{
> +    return false;
> +}
> +
>  void
>  print_dpdk_version(void)
>  {
> diff --git a/lib/dpdk.c b/lib/dpdk.c
> index 5c68ce4..ca072a1 100644
> --- a/lib/dpdk.c
> +++ b/lib/dpdk.c
> @@ -48,6 +48,7 @@ static char *vhost_sock_dir = NULL;   /* Location of vhost-user sockets */
>  static bool vhost_iommu_enabled = false; /* Status of vHost IOMMU support */
>  static bool dpdk_initialized = false; /* Indicates successful initialization
>                                         * of DPDK. */
> +static bool per_port_memory = false; /* Status of per port memory support */
>  
>  static int
>  process_vhost_flags(char *flag, const char *default_val, int size,
> @@ -384,6 +385,11 @@ dpdk_init__(const struct smap *ovs_other_config)
>      VLOG_INFO("IOMMU support for vhost-user-client %s.",
>                 vhost_iommu_enabled ? "enabled" : "disabled");
>  
> +    per_port_memory = smap_get_bool(ovs_other_config,
> +                                    "per-port-memory", false);
> +    VLOG_INFO("Per port mempool for DPDK devices %s.",
> +              per_port_memory ? "enabled" : "disabled");
> +
>      argv = grow_argv(&argv, 0, 1);
>      argc = 1;
>      argv[0] = xstrdup(ovs_get_program_name());
> @@ -541,6 +547,12 @@ dpdk_vhost_iommu_enabled(void)
>      return vhost_iommu_enabled;
>  }
>  
> +bool
> +dpdk_per_port_memory(void)
> +{
> +    return per_port_memory;
> +}
> +
>  void
>  dpdk_set_lcore_id(unsigned cpu)
>  {
> diff --git a/lib/dpdk.h b/lib/dpdk.h
> index efdaa63..bbb89d4 100644
> --- a/lib/dpdk.h
> +++ b/lib/dpdk.h
> @@ -39,6 +39,7 @@ void dpdk_init(const struct smap *ovs_other_config);
>  void dpdk_set_lcore_id(unsigned cpu);
>  const char *dpdk_get_vhost_sock_dir(void);
>  bool dpdk_vhost_iommu_enabled(void);
> +bool dpdk_per_port_memory(void);
>  void print_dpdk_version(void);
>  void dpdk_status(const struct ovsrec_open_vswitch *);
>  #endif /* dpdk.h */
> diff --git a/lib/netdev-dpdk.c b/lib/netdev-dpdk.c
> index 1bde9cf..c08b4f2 100644
> --- a/lib/netdev-dpdk.c
> +++ b/lib/netdev-dpdk.c
> @@ -91,13 +91,24 @@ static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(5, 20);
>  #define NETDEV_DPDK_MBUF_ALIGN      1024
>  #define NETDEV_DPDK_MAX_PKT_LEN     9728
>  
> -/* Min number of packets in the mempool.  OVS tries to allocate a mempool with
> - * roughly estimated number of mbufs: if this fails (because the system doesn't
> - * have enough hugepages) we keep halving the number until the allocation
> - * succeeds or we reach MIN_NB_MBUF */
> +/* Max and min number of packets in the mempool.  OVS tries to allocate a
> + * mempool with MAX_NB_MBUF: if this fails (because the system doesn't have
> + * enough hugepages) we keep halving the number until the allocation succeeds
> + * or we reach MIN_NB_MBUF */
> +
> +#define MAX_NB_MBUF          (4096 * 64)
>  #define MIN_NB_MBUF          (4096 * 4)
>  #define MP_CACHE_SZ          RTE_MEMPOOL_CACHE_MAX_SIZE
>  
> +/* MAX_NB_MBUF can be divided by 2 many times, until MIN_NB_MBUF */
> +BUILD_ASSERT_DECL(MAX_NB_MBUF % ROUND_DOWN_POW2(MAX_NB_MBUF / MIN_NB_MBUF)
> +                  == 0);
> +
> +/* The smallest possible NB_MBUF that we're going to try should be a multiple
> + * of MP_CACHE_SZ. This is advised by DPDK documentation. */
> +BUILD_ASSERT_DECL((MAX_NB_MBUF / ROUND_DOWN_POW2(MAX_NB_MBUF / MIN_NB_MBUF))
> +                  % MP_CACHE_SZ == 0);
> +
>  /*
>   * DPDK XSTATS Counter names definition
>   */
> @@ -297,12 +308,14 @@ static struct ovs_mutex dpdk_mp_mutex OVS_ACQ_AFTER(dpdk_mutex)
>      = OVS_MUTEX_INITIALIZER;
>  
>  /* Contains all 'struct dpdk_mp's. */
> -static struct ovs_list dpdk_mp_free_list OVS_GUARDED_BY(dpdk_mp_mutex)
> -    = OVS_LIST_INITIALIZER(&dpdk_mp_free_list);
> +static struct ovs_list dpdk_mp_list OVS_GUARDED_BY(dpdk_mp_mutex)
> +    = OVS_LIST_INITIALIZER(&dpdk_mp_list);
>  
> -/* Wrapper for a mempool released but not yet freed. */
>  struct dpdk_mp {
>       struct rte_mempool *mp;
> +     int mtu;
> +     int socket_id;
> +     int refcount;
>       struct ovs_list list_node OVS_GUARDED_BY(dpdk_mp_mutex);
>   };
>  
> @@ -384,7 +397,7 @@ struct netdev_dpdk {
>  
>      PADDED_MEMBERS_CACHELINE_MARKER(CACHE_LINE_SIZE, cacheline1,
>          struct ovs_mutex mutex OVS_ACQ_AFTER(dpdk_mutex);
> -        struct rte_mempool *mp;
> +        struct dpdk_mp *dpdk_mp;
>  
>          /* virtio identifier for vhost devices */
>          ovsrcu_index vid;
> @@ -550,68 +563,89 @@ dpdk_mp_full(const struct rte_mempool *mp) OVS_REQUIRES(dpdk_mp_mutex)
>  
>  /* Free unused mempools. */
>  static void
> -dpdk_mp_sweep(void)
> +dpdk_mp_sweep(void) OVS_REQUIRES(dpdk_mp_mutex)
>  {
>      struct dpdk_mp *dmp, *next;
>  
> -    ovs_mutex_lock(&dpdk_mp_mutex);
> -    LIST_FOR_EACH_SAFE (dmp, next, list_node, &dpdk_mp_free_list) {
> -        if (dpdk_mp_full(dmp->mp)) {
> +    LIST_FOR_EACH_SAFE (dmp, next, list_node, &dpdk_mp_list) {
> +        if (!dmp->refcount && dpdk_mp_full(dmp->mp)) {
>              VLOG_DBG("Freeing mempool \"%s\"", dmp->mp->name);
>              ovs_list_remove(&dmp->list_node);
>              rte_mempool_free(dmp->mp);
>              rte_free(dmp);
>          }
>      }
> -    ovs_mutex_unlock(&dpdk_mp_mutex);
>  }
>  
> -/* Ensure a mempool will not be freed. */
> -static void
> -dpdk_mp_do_not_free(struct rte_mempool *mp) OVS_REQUIRES(dpdk_mp_mutex)
> +/* Calculating the required number of mbufs differs depending on the
> + * mempool model being used. Check if per port mempools are in use before
> + * calculating.
> + */
> +static uint32_t
> +dpdk_calculate_mbufs(struct netdev_dpdk *dev, int mtu, bool per_port_mp)
>  {
> -    struct dpdk_mp *dmp, *next;
> +    uint32_t n_mbufs;
>  
> -    LIST_FOR_EACH_SAFE (dmp, next, list_node, &dpdk_mp_free_list) {
> -        if (dmp->mp == mp) {
> -            VLOG_DBG("Removing mempool \"%s\" from free list", dmp->mp->name);
> -            ovs_list_remove(&dmp->list_node);
> -            rte_free(dmp);
> -            break;
> +    if (!per_port_mp) {
> +        /* Shared mempools are being used.
> +         * XXX: this is a really rough method of provisioning memory.
> +         * It's impossible to determine what the exact memory requirements are
> +         * when the number of ports and rxqs that utilize a particular mempool
> +         * can change dynamically at runtime. For now, use this rough
> +         * heurisitic.
> +         */
> +        if (mtu >= ETHER_MTU) {
> +            n_mbufs = MAX_NB_MBUF;
> +        } else {
> +            n_mbufs = MIN_NB_MBUF;
>          }
> +    } else {
> +        /* Per port mempools are being used.
> +         * XXX: rough estimation of number of mbufs required for this port:
> +         * <packets required to fill the device rxqs>
> +         * + <packets that could be stuck on other ports txqs>
> +         * + <packets in the pmd threads>
> +         * + <additional memory for corner cases>
> +         */
> +        n_mbufs = dev->requested_n_rxq * dev->requested_rxq_size
> +                  + dev->requested_n_txq * dev->requested_txq_size
> +                  + MIN(RTE_MAX_LCORE, dev->requested_n_rxq) * NETDEV_MAX_BURST
> +                  + MIN_NB_MBUF;
>      }
> +
> +    return n_mbufs;
>  }
>  
> -/* Returns a valid pointer when either of the following is true:
> - *  - a new mempool was just created;
> - *  - a matching mempool already exists. */
> -static struct rte_mempool *
> -dpdk_mp_create(struct netdev_dpdk *dev, int mtu)
> +static struct dpdk_mp *
> +dpdk_mp_create(struct netdev_dpdk *dev, int mtu, bool per_port_mp)
>  {
>      char mp_name[RTE_MEMPOOL_NAMESIZE];
>      const char *netdev_name = netdev_get_name(&dev->up);
>      int socket_id = dev->requested_socket_id;
>      uint32_t n_mbufs;
>      uint32_t hash = hash_string(netdev_name, 0);
> -    struct rte_mempool *mp = NULL;
> -
> -    /*
> -     * XXX: rough estimation of number of mbufs required for this port:
> -     * <packets required to fill the device rxqs>
> -     * + <packets that could be stuck on other ports txqs>
> -     * + <packets in the pmd threads>
> -     * + <additional memory for corner cases>
> -     */
> -    n_mbufs = dev->requested_n_rxq * dev->requested_rxq_size
> -              + dev->requested_n_txq * dev->requested_txq_size
> -              + MIN(RTE_MAX_LCORE, dev->requested_n_rxq) * NETDEV_MAX_BURST
> -              + MIN_NB_MBUF;
> +    struct dpdk_mp *dmp = NULL;
> +    int ret;
> +
> +    dmp = dpdk_rte_mzalloc(sizeof *dmp);
> +    if (!dmp) {
> +        return NULL;
> +    }
> +    dmp->socket_id = socket_id;
> +    dmp->mtu = mtu;
> +    dmp->refcount = 1;
> +
> +    n_mbufs = dpdk_calculate_mbufs(dev, mtu, per_port_mp);
>  
> -    ovs_mutex_lock(&dpdk_mp_mutex);
>      do {
>          /* Full DPDK memory pool name must be unique and cannot be
> -         * longer than RTE_MEMPOOL_NAMESIZE. */
> -        int ret = snprintf(mp_name, RTE_MEMPOOL_NAMESIZE,
> +         * longer than RTE_MEMPOOL_NAMESIZE. Note that for the shared
> +         * mempool case this can result in one device using a mempool
> +         * which references a different device in it's name. However as
> +         * mempool names are hashed, the device name will not be readable
> +         * so this is not an issue for tasks such as debugging.
> +         */
> +        ret = snprintf(mp_name, RTE_MEMPOOL_NAMESIZE,
>                             "ovs%08x%02d%05d%07u",
>                             hash, socket_id, mtu, n_mbufs);
>          if (ret < 0 || ret >= RTE_MEMPOOL_NAMESIZE) {
> @@ -627,96 +661,157 @@ dpdk_mp_create(struct netdev_dpdk *dev, int mtu)
>                    netdev_name, n_mbufs, socket_id,
>                    dev->requested_n_rxq, dev->requested_n_txq);
>  
> -        mp = rte_pktmbuf_pool_create(mp_name, n_mbufs, MP_CACHE_SZ,
> -                 sizeof (struct dp_packet) - sizeof (struct rte_mbuf),
> -                 MBUF_SIZE(mtu) - sizeof(struct dp_packet), socket_id);
> +        dmp->mp = rte_pktmbuf_pool_create(mp_name, n_mbufs,
> +                                          MP_CACHE_SZ,
> +                                          sizeof (struct dp_packet)
> +                                          - sizeof (struct rte_mbuf),
> +                                          MBUF_SIZE(mtu)
> +                                          - sizeof(struct dp_packet),
> +                                          socket_id);
>  
> -        if (mp) {
> +        if (dmp->mp) {
>              VLOG_DBG("Allocated \"%s\" mempool with %u mbufs",
>                       mp_name, n_mbufs);
>              /* rte_pktmbuf_pool_create has done some initialization of the
> -             * rte_mbuf part of each dp_packet. Some OvS specific fields
> -             * of the packet still need to be initialized by
> -             * ovs_rte_pktmbuf_init. */
> -            rte_mempool_obj_iter(mp, ovs_rte_pktmbuf_init, NULL);
> +             * rte_mbuf part of each dp_packet, while ovs_rte_pktmbuf_init
> +             * initializes some OVS specific fields of dp_packet.
> +             */
> +            rte_mempool_obj_iter(dmp->mp, ovs_rte_pktmbuf_init, NULL);
> +            return dmp;
>          } else if (rte_errno == EEXIST) {
>              /* A mempool with the same name already exists.  We just
>               * retrieve its pointer to be returned to the caller. */
> -            mp = rte_mempool_lookup(mp_name);
> +            dmp->mp = rte_mempool_lookup(mp_name);
>              /* As the mempool create returned EEXIST we can expect the
>               * lookup has returned a valid pointer.  If for some reason
>               * that's not the case we keep track of it. */
>              VLOG_DBG("A mempool with name \"%s\" already exists at %p.",
> -                     mp_name, mp);
> -            /* Ensure this reused mempool will not be freed. */
> -            dpdk_mp_do_not_free(mp);
> +                     mp_name, dmp->mp);
> +            return dmp;
>          } else {
> -            VLOG_ERR("Failed mempool \"%s\" create request of %u mbufs",
> -                     mp_name, n_mbufs);
> +            VLOG_DBG("Failed to create mempool \"%s\" with a request of "
> +                     "%u mbufs, retrying with %u mbufs",
> +                     mp_name, n_mbufs, n_mbufs / 2);
>          }
> -    } while (!mp && rte_errno == ENOMEM && (n_mbufs /= 2) >= MIN_NB_MBUF);
> +    } while (!dmp->mp && rte_errno == ENOMEM && (n_mbufs /= 2) >= MIN_NB_MBUF);
>  
> -    ovs_mutex_unlock(&dpdk_mp_mutex);
> -    return mp;
> +    VLOG_ERR("Failed to create mempool \"%s\" with a request of %u mbufs",
> +             mp_name, n_mbufs);
> +
> +    rte_free(dmp);
> +    return NULL;
>  }
>  
> -/* Release an existing mempool. */
> -static void
> -dpdk_mp_release(struct rte_mempool *mp)
> +static struct dpdk_mp *
> +dpdk_mp_get(struct netdev_dpdk *dev, int mtu, bool per_port_mp)
>  {
> -    if (!mp) {
> -        return;
> -    }
> +    struct dpdk_mp *dmp, *next;
> +    bool reuse = false;
>  
>      ovs_mutex_lock(&dpdk_mp_mutex);
> -    if (dpdk_mp_full(mp)) {
> -        VLOG_DBG("Freeing mempool \"%s\"", mp->name);
> -        rte_mempool_free(mp);
> -    } else {
> -        struct dpdk_mp *dmp;
> +    /* Check if shared mempools are being used, if so check existing mempools
> +     * to see if reuse is possible. */
> +    if (!per_port_mp) {
> +        LIST_FOR_EACH (dmp, list_node, &dpdk_mp_list) {
> +            if (dmp->socket_id == dev->requested_socket_id
> +                && dmp->mtu == mtu) {
> +                VLOG_DBG("Reusing mempool \"%s\"", dmp->mp->name);
> +                dmp->refcount++;
> +                reuse = true;
> +                break;
> +            }
> +        }
> +    }
> +    /* Sweep mempools after reuse or before create. */
> +    dpdk_mp_sweep();
>  
> -        dmp = dpdk_rte_mzalloc(sizeof *dmp);
> +    if (!reuse) {
> +        dmp = dpdk_mp_create(dev, mtu, per_port_mp);
>          if (dmp) {
> -            dmp->mp = mp;
> -            ovs_list_push_back(&dpdk_mp_free_list, &dmp->list_node);
> +            /* Shared mempools will hit the reuse case above so will not
> +             * request a mempool that already exists but we need to check
> +             * for the EEXIST case for per port memory case. Compare the
> +             * mempool returned by dmp to each entry in dpdk_mp_list. If a
> +             * match is found, free dmp as a new entry is not required, set
> +             * dmp to point to the existing entry and increment the refcount
> +             * to avoid being freed at a later stage.
> +             */
> +            if (per_port_mp && rte_errno == EEXIST) {
> +                LIST_FOR_EACH (next, list_node, &dpdk_mp_list) {
> +                    if (dmp->mp == next->mp) {
> +                        rte_free(dmp);
> +                        dmp = next;
> +                        dmp->refcount++;
> +                    }
> +                }
> +            } else {
> +                ovs_list_push_back(&dpdk_mp_list, &dmp->list_node);
> +            }
>          }
>      }
> +
> +
> +    ovs_mutex_unlock(&dpdk_mp_mutex);
> +
> +    return dmp;
> +}
> +
> +/* Decrement reference to a mempool. */
> +static void
> +dpdk_mp_put(struct dpdk_mp *dmp)
> +{
> +    if (!dmp) {
> +        return;
> +    }
> +
> +    ovs_mutex_lock(&dpdk_mp_mutex);
> +    ovs_assert(dmp->refcount);
> +    dmp->refcount--;
>      ovs_mutex_unlock(&dpdk_mp_mutex);
>  }
>  
> -/* Tries to allocate a new mempool - or re-use an existing one where
> - * appropriate - on requested_socket_id with a size determined by
> - * requested_mtu and requested Rx/Tx queues.
> - * On success - or when re-using an existing mempool - the new configuration
> - * will be applied.
> +/* Depending on the memory model being used this function tries
> + * identify and reuse an existing mempool or tries to allocate new
> + * mempool on requested_socket_id with mbuf size corresponding to
> + * requested_mtu. On success new configuration will be applied.
>   * On error, device will be left unchanged. */
>  static int
>  netdev_dpdk_mempool_configure(struct netdev_dpdk *dev)
>      OVS_REQUIRES(dev->mutex)
>  {
>      uint32_t buf_size = dpdk_buf_size(dev->requested_mtu);
> -    struct rte_mempool *mp;
> +    struct dpdk_mp *dmp;
>      int ret = 0;
> +    bool per_port_mp = dpdk_per_port_memory();
>  
> -    dpdk_mp_sweep();
> +    /* With shared mempools we do not need to configure a mempool if the MTU
> +     * and socket ID have not changed, the previous configuration is still
> +     * valid so return 0 */
> +    if (!per_port_mp && dev->mtu == dev->requested_mtu
> +        && dev->socket_id == dev->requested_socket_id) {
> +        return ret;
> +    }
>  
> -    mp = dpdk_mp_create(dev, FRAME_LEN_TO_MTU(buf_size));
> -    if (!mp) {
> +    dmp = dpdk_mp_get(dev, FRAME_LEN_TO_MTU(buf_size), per_port_mp);
> +    if (!dmp) {
>          VLOG_ERR("Failed to create memory pool for netdev "
>                   "%s, with MTU %d on socket %d: %s\n",
>                   dev->up.name, dev->requested_mtu, dev->requested_socket_id,
>                   rte_strerror(rte_errno));
> -        ret = rte_errno;
> +        return rte_errno;
>      } else {
> -        /* If a new MTU was requested and its rounded value equals the one
> -         * that is currently used, then the existing mempool is returned. */
> -        if (dev->mp != mp) {
> -            /* A new mempool was created, release the previous one. */
> -            dpdk_mp_release(dev->mp);
> -        } else {
> -            ret = EEXIST;
> +        /* Check for any pre-existing dpdk_mp for the device before accessing
> +         * the associated mempool.
> +         */
> +        if (dev->dpdk_mp != NULL) {
> +            /* A new MTU was requested and its rounded value does not
> +             * equal the rounded value of the current mempool, decrement
> +             * the reference count to the devices current dpdk_mp as its
> +             * associated mempool will not be used for this device.
> +             */
> +            dpdk_mp_put(dev->dpdk_mp);
>          }
> -        dev->mp = mp;
> +        dev->dpdk_mp = dmp;
>          dev->mtu = dev->requested_mtu;
>          dev->socket_id = dev->requested_socket_id;
>          dev->max_packet_len = MTU_TO_FRAME_LEN(dev->mtu);
> @@ -855,7 +950,8 @@ dpdk_eth_dev_port_config(struct netdev_dpdk *dev, int n_rxq, int n_txq)
>  
>          for (i = 0; i < n_rxq; i++) {
>              diag = rte_eth_rx_queue_setup(dev->port_id, i, dev->rxq_size,
> -                                          dev->socket_id, NULL, dev->mp);
> +                                          dev->socket_id, NULL,
> +                                          dev->dpdk_mp->mp);
>              if (diag) {
>                  VLOG_INFO("Interface %s unable to setup rxq(%d): %s",
>                            dev->up.name, i, rte_strerror(-diag));
> @@ -950,7 +1046,7 @@ dpdk_eth_dev_init(struct netdev_dpdk *dev)
>      memcpy(dev->hwaddr.ea, eth_addr.addr_bytes, ETH_ADDR_LEN);
>      rte_eth_link_get_nowait(dev->port_id, &dev->link);
>  
> -    mbp_priv = rte_mempool_get_priv(dev->mp);
> +    mbp_priv = rte_mempool_get_priv(dev->dpdk_mp->mp);
>      dev->buf_size = mbp_priv->mbuf_data_room_size - RTE_PKTMBUF_HEADROOM;
>  
>      /* Get the Flow control configuration for DPDK-ETH */
> @@ -1204,7 +1300,7 @@ common_destruct(struct netdev_dpdk *dev)
>      OVS_EXCLUDED(dev->mutex)
>  {
>      rte_free(dev->tx_q);
> -    dpdk_mp_release(dev->mp);
> +    dpdk_mp_put(dev->dpdk_mp);
>  
>      ovs_list_remove(&dev->list_node);
>      free(ovsrcu_get_protected(struct ingress_policer *,
> @@ -1957,7 +2053,7 @@ netdev_dpdk_vhost_rxq_recv(struct netdev_rxq *rxq,
>          return EAGAIN;
>      }
>  
> -    nb_rx = rte_vhost_dequeue_burst(vid, qid, dev->mp,
> +    nb_rx = rte_vhost_dequeue_burst(vid, qid, dev->dpdk_mp->mp,
>                                      (struct rte_mbuf **) batch->packets,
>                                      NETDEV_MAX_BURST);
>      if (!nb_rx) {
> @@ -2196,7 +2292,7 @@ dpdk_do_tx_copy(struct netdev *netdev, int qid, struct dp_packet_batch *batch)
>              continue;
>          }
>  
> -        pkts[txcnt] = rte_pktmbuf_alloc(dev->mp);
> +        pkts[txcnt] = rte_pktmbuf_alloc(dev->dpdk_mp->mp);
>          if (OVS_UNLIKELY(!pkts[txcnt])) {
>              dropped += cnt - i;
>              break;
> @@ -3075,7 +3171,7 @@ netdev_dpdk_get_mempool_info(struct unixctl_conn *conn,
>          ovs_mutex_lock(&dev->mutex);
>          ovs_mutex_lock(&dpdk_mp_mutex);
>  
> -        rte_mempool_dump(stream, dev->mp);
> +        rte_mempool_dump(stream, dev->dpdk_mp->mp);
>  
>          ovs_mutex_unlock(&dpdk_mp_mutex);
>          ovs_mutex_unlock(&dev->mutex);
> @@ -3772,7 +3868,7 @@ dpdk_vhost_reconfigure_helper(struct netdev_dpdk *dev)
>  
>      err = netdev_dpdk_mempool_configure(dev);
>      if (!err) {
> -        /* A new mempool was created. */
> +        /* A new mempool was created or re-used. */
>          netdev_change_seq_changed(&dev->up);
>      } else if (err != EEXIST){
>          return err;
> diff --git a/vswitchd/vswitch.xml b/vswitchd/vswitch.xml
> index b93da69..b9aba8c 100644
> --- a/vswitchd/vswitch.xml
> +++ b/vswitchd/vswitch.xml
> @@ -360,6 +360,23 @@
>          </p>
>        </column>
>  
> +      <column name="other_config" key="per-port-memory"
> +              type='{"type": "boolean"}'>
> +        <p>
> +          By default OVS DPDK uses a shared memory model wherein devices
> +          that have the same MTU and socket values can share the same
> +          mempool. Setting this value to <code>true</code> changes this
> +          behaviour. Per port memory allow DPDK devices to use private
> +          memory per device. This can provide greater transapraency as
                                                         ^ transparency

Just one additional spelling mistake :)

> +          regards memory usage but potentially at the cost of greater memory
> +          requirements.
> +        </p>
> +        <p>
> +          Changing this value requires restarting the daemon if dpdk-init has
> +          already been set to true.
> +        </p>
> +      </column>
> +
>        <column name="other_config" key="tx-flush-interval"
>                type='{"type": "integer",
>                       "minInteger": 0, "maxInteger": 1000000}'>


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