On Tue, 3 Nov 2026 11:04:39 +0000 Dariusz Sosnowski <[email protected]> wrote:
> > -----Original Message----- > > From: Stephen Hemminger <[email protected]> > > Sent: Monday, November 2, 2026 9:08 AM > > To: Dariusz Sosnowski <[email protected]> > > Cc: Slava Ovsiienko <[email protected]>; Bing Zhao > > <[email protected]>; Ori Kam <[email protected]>; Suanming Mou > > <[email protected]>; Matan Azrad <[email protected]>; > > [email protected] > > Subject: Re: [PATCH v2 0/2] net/mlx5: improvements to link status handling > > > > On Fri, 30 Oct 2026 18:28:41 +0100 > > Dariusz Sosnowski <[email protected]> wrote: > > > > > This series is a result of splitting patch: > > > https://patches.dpdk.org/project/dpdk/patch/20261026160400.1290443-1- > > d > > > [email protected]/ > > > > > > Patch 1 - Fix for mlx5 link update function to query current link > > > carrier status, bypassing the delay introduced by linkwatch in Linux > > > kernel. > > > > > > Patch 2 - Move to link status polling, in place of relying on netlink > > > events which can be delayed by linkwatch for up to 1s. > > > > Instead of polling is there a way to get the lsc directly from devx or ibv > > on > > mlx5? That would work around the issue and avoid the overhead. > > From DevX, unfortunately no. > > In ibv there are 2 options: > > - IBV_EVENT_PORT_ACTIVE/ERR - generated on up/down respectively; > On ethernet devices, these are generated from netdev carrier state, so they > are > subjected to the same linkwatch delay. > > - IBV_EVENT_DEVICE_SPEED_CHANGE - generated on up and down; > Is generated immediately on FW event reception. > It is available from Linux kernel v7.0 and rdma-core v62.0. > > IBV_EVENT_DEVICE_SPEED_CHANGE would be ideal here, > but there's no good way to discover whether currently running kernel supports > it. > > Theoretically, this event was added alongside ibv_query_port_speed() IB verb. > Following logic could be implemented (for DPDK compiled with recent rdma-core) > > - Call ibv_query_port_speed() > - If error: > - start listening on device speed change async event > - on event: query link status of DPDK ports on that device > - else if ENOTSUP: > - start link status poll loop > > > > > Long term, it would be good if kernel had sysctl to set linkwatch per > > interface > > but it doesn't I have a patch to allow link watch timeout to be set via netlink or sysfs. But needs more testing. In future, mlx5 could detect and configure that.
