Querying link status may get delayed for an undeterministic (long) time
with mlx5 ports. This is a consequence of the mlx5 driver calling ethtool
kernel API and getting stuck on the kernel RTNL lock while some other
operation is in progress under this lock.
One impact for long link status query is that it is called under the bond
lock taken in write mode periodically in bond_run().
In parallel, datapath threads may block requesting to read bonding related
info (like for example in bond_check_admissibility()).
The LSC interrupt mode is available with many DPDK drivers and is used by
default with testpmd.
It seems safe enough to switch on this feature by default in OVS.
We keep the per interface option to disable this feature in case of an
unforeseen bug.
Signed-off-by: David Marchand <david.march...@redhat.com>
---
Changes since v1:
- (early) fail when interrupt lsc is requested by user but not supported
by the driver,
- otherwise, log a debug message if user did not request interrupt mode,
---
Documentation/topics/dpdk/phy.rst | 4 ++--
NEWS | 3 +++
lib/netdev-dpdk.c | 13 ++++++++++++-
vswitchd/vswitch.xml | 8 ++++----
4 files changed, 21 insertions(+), 7 deletions(-)
diff --git a/Documentation/topics/dpdk/phy.rst
b/Documentation/topics/dpdk/phy.rst
index efd168cba8..eefc25613d 100644
--- a/Documentation/topics/dpdk/phy.rst
+++ b/Documentation/topics/dpdk/phy.rst
@@ -546,8 +546,8 @@ the firmware every time to fulfil this request.
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``.
+The default configuration is interrupt mode. To set polling mode, option
+``dpdk-lsc-interrupt`` has to be set to ``false``.
Command to set interrupt mode for a specific interface::
$ ovs-vsctl set interface <iface_name> options:dpdk-lsc-interrupt=true
diff --git a/NEWS b/NEWS
index 5ae0108d55..1e19beb793 100644
--- a/NEWS
+++ b/NEWS
@@ -9,6 +9,9 @@ Post-v3.3.0
https://github.com/openvswitch/ovs.git
- DPDK:
* OVS validated with DPDK 23.11.1.
+ * Link status changes are now handled via interrupt mode if the DPDK
+ driver supports it. It is possible to revert to polling mode by setting
+ per interface 'dpdk-lsc-interrupt' other_config to 'false'.
v3.3.0 - 16 Feb 2024
diff --git a/lib/netdev-dpdk.c b/lib/netdev-dpdk.c
index 0fa37d5145..a260bc8485 100644
--- a/lib/netdev-dpdk.c
+++ b/lib/netdev-dpdk.c
@@ -2397,7 +2397,18 @@ netdev_dpdk_set_config(struct netdev *netdev, const
struct smap *args,
}
}
- lsc_interrupt_mode = smap_get_bool(args, "dpdk-lsc-interrupt", false);
+ lsc_interrupt_mode = smap_get_bool(args, "dpdk-lsc-interrupt", true);
+ if (lsc_interrupt_mode && !(*info.dev_flags & RTE_ETH_DEV_INTR_LSC)) {
+ if (smap_get(args, "dpdk-lsc-interrupt")) {
+ VLOG_ERR("interface '%s': link status interrupt is not supported.",
+ netdev_get_name(netdev));
+ err = EINVAL;
+ goto out;
+ }
+ VLOG_DBG("interface '%s': not enabling link status interrupt.",
+ netdev_get_name(netdev));
+ lsc_interrupt_mode = false;
+ }
if (dev->requested_lsc_interrupt_mode != lsc_interrupt_mode) {
dev->requested_lsc_interrupt_mode = lsc_interrupt_mode;
netdev_request_reconfigure(netdev);
diff --git a/vswitchd/vswitch.xml b/vswitchd/vswitch.xml
index 8a1b607d71..e3afb78a4e 100644
--- a/vswitchd/vswitch.xml
+++ b/vswitchd/vswitch.xml
@@ -4647,12 +4647,12 @@ ovs-vsctl add-port br0 p0 -- set Interface p0
type=patch options:peer=p1 \
<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.
+ Set this value to <code>false</code> to configure poll mode for
+ Link State Change (LSC) detection instead of interrupt mode for the
+ DPDK interface.
</p>
<p>
- If this value is not set, poll mode is configured.
+ If this value is not set, interrupt mode is configured.
</p>
<p>
This parameter has an effect only on netdev dpdk interfaces.
--
2.44.0
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