[ovs-dev] [PATCH v2] dpdk: Support both shared and per port mempools.

Ian Stokes ian.stokes at intel.com
Wed Jun 27 13:58:31 UTC 2018


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>
---
v1 -> v2
* Fix typo 'transparency' in vswitch.xml.
* In memory.rst change mtu size description from 'can be' to 'is always'
  larger than the requested mtu size and fix 'alignment' typo.
* Fix typo in function description comment for
  netdev_dpdk_mempool_configure().
* Set ret = to rte_errno and return before exiting the function
  netdev_dpdk_mempool_configure() instead of returning rte_errno
  immediately.
* Update comment to explain why returned dpdk_mempools refcounts are
  decremented in netdev_dpdk_mempool_configure() for reuse and EEXIST
  cases.
---
 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, 458 insertions(+), 99 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..e5fb166
--- /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 is always larger than the requested MTU size due to
+   alignment 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..dc68af2 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 memory is 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 memory 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 memory is 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 +661,159 @@ 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 memory is 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 memory 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 to
+ * identify and reuse an existing mempool or tries to allocate a new
+ * mempool on requested_socket_id with mbuf size corresponding to the
+ * requested_mtu. On success, a 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 memory 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;
     } 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, decrement the reference count for the
+             * devices current dpdk_mp. This is required even if a pointer to
+             * same dpdk_mp is returned by dpdk_mp_get. The refcount for dmp
+             * has already been incremented by dpdk_mp_get at this stage so it
+             * must be decremented to keep an accurate refcount for the
+             * dpdk_mp.
+             */
+            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 +952,8 @@ 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 +1048,7 @@ 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 +1302,7 @@ 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 +2055,7 @@ 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 +2294,7 @@ 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 +3173,7 @@ 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 +3870,7 @@ 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..ec06349 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 transparency as
+          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}'>
-- 
2.7.5



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