[ovs-dev] [PATCH v5] Configurable Link State Change (LSC) detection mode
Róbert Mulik
robert.mulik at ericsson.com
Wed Feb 21 10:33:21 UTC 2018
> -----Original Message-----
> From: ovs-dev-bounces at openvswitch.org [mailto:ovs-dev-
> bounces at openvswitch.org] On Behalf Of Eelco Chaudron
> Sent: Tuesday, February 20, 2018 3:17 PM
> To: ovs-dev at openvswitch.org
> Subject: Re: [ovs-dev] [PATCH v5] Configurable Link State Change (LSC)
> detection mode
>
> Hi Robert,
>
> I did not see a reply to my v4 reply, so I ask this question again:
> Did you try what happens if the PMD does not support LSC and its
> enabled?
Unfortunately I don't have any cards which don't support LSC, so I couldn't test it
>
> Also, it would be easier to understand what you are going to change if
> you answer the questions in the review emails.
>
> For example, this patch is missing the suggestion on adding the LSC
> config in netdev_dpdk_get_config(), as suggested by Ilya.
As I understand the reason for this function would be to avoid the confusion when
both global and local configs are configured for an interface, especially if we go with
the implementation where the global config doesn't take effect without service
restart.
Since the global config is not implemented in this patch and the default value remains
the same as it always was (poll mode) and also the documentation tells what the default
value is, I don't really see the importance of this implementation.
>
> I did a quick visual review below, and will wait for v6 with the above
> change, and do another test run.
>
> //Eelco
>
>
> On 15/02/18 15:44, Róbert Mulik wrote:
> > It is possible to change LSC detection mode to polling or interrupt mode
> > for DPDK interfaces. The default is polling mode. To set interrupt mode,
> > option dpdk-lsc-interrupt has to be set to true.
> >
> > In polling mode more processor time is needed, since the OVS repeatedly
> reads
> > the link state with a short period. It can lead to packet loss for certain
> > systems.
> >
> > In interrupt mode the hardware itself triggers an interrupt when link state
> > change happens, so less processing time needs for the OVS.
> >
> > For detailed description and usage see the dpdk install documentation.
> >
> > Signed-off-by: Robert Mulik <robert.mulik at ericsson.com>
> > ---
> > Documentation/intro/install/dpdk.rst | 35
> +++++++++++++++++++++++++++++++++++
> > lib/netdev-dpdk.c | 22 ++++++++++++++++++++--
> > vswitchd/vswitch.xml | 17 +++++++++++++++++
> > 3 files changed, 72 insertions(+), 2 deletions(-)
> >
> > diff --git a/Documentation/intro/install/dpdk.rst
> b/Documentation/intro/install/dpdk.rst
> > index ed358d5..e3872e7 100644
> > --- a/Documentation/intro/install/dpdk.rst
> > +++ b/Documentation/intro/install/dpdk.rst
> > @@ -628,6 +628,41 @@ The average number of packets per output batch
> can be checked in PMD stats::
> >
> > $ ovs-appctl dpif-netdev/pmd-stats-show
> >
> > +Link State Change (LSC) detection configuration
> > +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > +
> > +There are two methods to get the information when Link State Change
> (LSC)
> > +happens on a network interface: by polling or interrupt.
> > +
> > +With the polling method, the main process checks the link state on a
> > +fixed interval. This fixed interval determines how fast a link change is
> > +detected. Another problem with the poll mode is that on some hardware
> a
> > +polling cycle takes too much time, which (in the end) leads to packet loss
> > +for certain systems.
> Maybe we should stick to facts of the implementation, and not known
> bugs? So remove the "Another problem..."
> > +
> > +If interrupts are used to get LSC information, the hardware itself triggers
> > +an interrupt when link state change happens, the interrupt thread wakes
> up
> > +from sleep, updates the information, and goes back to sleep mode. When
> no link
> > +state change happens (most of the time), the thread remains in sleep
> mode and
> > +doesn`t use processor time at all. The disadvantage of this method is that
> > +when an interrupt happens, the processor has to handle it immediately,
> so it
> > +puts the currently running process to background, handles the interrupt,
> and
> > +takes the background process back.
> > +
> > +Note that not all PMD drivers support LSC interrupts.
> > +
> > +The default configuration is polling mode. To set interrupt mode, option
> > +``dpdk-lsc-interrupt`` has to be set to ``true``.
> > +
> > +Command to set interrupt mode for a specific interface::
> > + $ ovs-vsctl set interface <iface_name> options:dpdk-lsc-interrupt=true
> > +
> > +Command to set polling mode for a specific interface::
> > + $ ovs-vsctl set interface <iface_name> options:dpdk-lsc-interrupt=false
> > +
> > +Command to remove ``dpdk-lsc-interrupt`` option::
> > + $ ovs-vsctl remove interface <iface_name> options dpdk-lsc-interrupt
> > +
> > Limitations
> > ------------
> >
> > diff --git a/lib/netdev-dpdk.c b/lib/netdev-dpdk.c
> > index 94fb163..d092ef1 100644
> > --- a/lib/netdev-dpdk.c
> > +++ b/lib/netdev-dpdk.c
> > @@ -433,6 +433,12 @@ struct netdev_dpdk {
> > /* DPDK-ETH hardware offload features,
> > * from the enum set 'dpdk_hw_ol_features' */
> > uint32_t hw_ol_features;
> > +
> > + /* Properties for link state change detection mode.
> > + * If lsc_interrupt_mode is set to false, poll mode is used,
> > + * otherwise interrupt mode is used. */
> > + bool requested_lsc_interrupt_mode;
> > + bool lsc_interrupt_mode;
> > );
> >
> > PADDED_MEMBERS(CACHE_LINE_SIZE,
> > @@ -686,12 +692,14 @@ dpdk_watchdog(void *dummy OVS_UNUSED)
> > }
> >
> > static int
> > -dpdk_eth_dev_queue_setup(struct netdev_dpdk *dev, int n_rxq, int
> n_txq)
> > +dpdk_eth_dev_port_config(struct netdev_dpdk *dev, int n_rxq, int
> n_txq)
> > {
> > int diag = 0;
> > int i;
> > struct rte_eth_conf conf = port_conf;
> >
> > + conf.intr_conf.lsc = dev->lsc_interrupt_mode;
> > +
> > /* For some NICs (e.g. Niantic), scatter_rx mode needs to be explicitly
> > * enabled. */
> > if (dev->mtu > ETHER_MTU) {
> > @@ -801,7 +809,7 @@ dpdk_eth_dev_init(struct netdev_dpdk *dev)
> > n_rxq = MIN(info.max_rx_queues, dev->up.n_rxq);
> > n_txq = MIN(info.max_tx_queues, dev->up.n_txq);
> >
> > - diag = dpdk_eth_dev_queue_setup(dev, n_rxq, n_txq);
> > + diag = dpdk_eth_dev_port_config(dev, n_rxq, n_txq);
> > if (diag) {
> > VLOG_ERR("Interface %s(rxq:%d txq:%d) configure error: %s",
> > dev->up.name, n_rxq, n_txq, rte_strerror(-diag));
> > @@ -897,6 +905,7 @@ common_construct(struct netdev *netdev,
> dpdk_port_t port_no,
> > dev->flags = 0;
> > dev->requested_mtu = ETHER_MTU;
> > dev->max_packet_len = MTU_TO_FRAME_LEN(dev->mtu);
> > + dev->requested_lsc_interrupt_mode = 0;
> > ovsrcu_index_init(&dev->vid, -1);
> > dev->vhost_reconfigured = false;
> > dev->attached = false;
> > @@ -1520,6 +1529,12 @@ netdev_dpdk_set_config(struct netdev
> *netdev, const struct smap *args,
> > goto out;
> > }
> >
> > + bool lsc_interrupt_mode = smap_get_bool(args, "dpdk-lsc-interrupt",
> false);
> > + if (dev->requested_lsc_interrupt_mode != lsc_interrupt_mode) {
> > + dev->requested_lsc_interrupt_mode = lsc_interrupt_mode;
> > + netdev_request_reconfigure(netdev);
> > + }
> > +
> > rx_fc_en = smap_get_bool(args, "rx-flow-ctrl", false);
> > tx_fc_en = smap_get_bool(args, "tx-flow-ctrl", false);
> > autoneg = smap_get_bool(args, "flow-ctrl-autoneg", false);
> > @@ -3546,6 +3561,7 @@ netdev_dpdk_reconfigure(struct netdev
> *netdev)
> > if (netdev->n_txq == dev->requested_n_txq
> > && netdev->n_rxq == dev->requested_n_rxq
> > && dev->mtu == dev->requested_mtu
> > + && dev->lsc_interrupt_mode == dev-
> >requested_lsc_interrupt_mode
> > && dev->rxq_size == dev->requested_rxq_size
> > && dev->txq_size == dev->requested_txq_size
> > && dev->socket_id == dev->requested_socket_id) {
> > @@ -3561,6 +3577,8 @@ netdev_dpdk_reconfigure(struct netdev
> *netdev)
> > goto out;
> > }
> >
> > + dev->lsc_interrupt_mode = dev->requested_lsc_interrupt_mode;
> > +
> > netdev->n_txq = dev->requested_n_txq;
> > netdev->n_rxq = dev->requested_n_rxq;
> >
> > diff --git a/vswitchd/vswitch.xml b/vswitchd/vswitch.xml
> > index 0c6a43d..3c9e637 100644
> > --- a/vswitchd/vswitch.xml
> > +++ b/vswitchd/vswitch.xml
> > @@ -3631,6 +3631,23 @@ ovs-vsctl add-port br0 p0 -- set Interface p0
> type=patch options:peer=p1 \
> > </column>
> > </group>
> >
> > + <group title="Link State Change detection mode">
> > + <column name="options" key="dpdk-lsc-interrupt"
> > + type='{"type": "boolean"}'>
> > + <p>
> > + Set this value to <code>true</code> to configure interrupt mode for
> > + Link State Change (LSC) detection instead of poll mode for the DPDK
> > + interface.
> > + </p>
> > + <p>
> > + If this value is not set, poll mode is configured.
> > + </p>
> > + <p>
> > + This parameter has an effect only on netdev dpdk interfaces.
> > + </p>
> > + </column>
> > + </group>
> > +
> > <group title="Common Columns">
> > The overall purpose of these columns is described under
> <code>Common
> > Columns</code> at the beginning of this document.
> > --
> > 1.9.1
> >
> > _______________________________________________
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> > dev at openvswitch.org
> > https://mail.openvswitch.org/mailman/listinfo/ovs-dev
>
>
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