On 06/25/2018 12:56 PM, Ian Stokes wrote:
> 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 <[email protected]>
> ---
> 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
s/can be/is always/
> + allignment and rounding needed in OVS DPDK.
alignment
> +
> +Below are a number of examples of memory requirement calculations for both
> +shared and per port memory models.
> +
-----8<-----
>
> -/* 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
tries to
> + * 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;
No need to return here and have the else below. You could set ret or
remove the else.
> } 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.
> + */
The comment needs updating. You could be reusing the existing mempool,
in which case it's still ok to mp_put because you have just incremented
it...
About that, I know it was my comment to remove an unnecessary check here
:-/ but i'm wondering if the refcount inc and then dec for the EEXISTS
case is unintuitive and it would better the way you had it with set
refcount =1 in mp_get, and then have the check for "if (dev->dpdk_mp !=
dmp)" before you mp_put. What do you think?
> + 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
> + 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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