[dm-devel] dm-multipath - IO queue dispatch based on FPIN Congestion/Latency notifications.

[Martin Wilck]

On Wed, 2021-03-31 at 16:18 +0530, Muneendra Kumar M wrote:
> 
> > Talking about FPIN, is it planned to notify user space about such
> > fabric
> events, and if yes, how?
> 
> [Muneendra]Yes. FC drivers, when receiving FC FPIN ELS's are calling
> a
> scsi transport routine with the FPIN payload.  The transport
> is pushing this as an "event" via netlink.  An app bound to the local
> address used by the scsi transport can receive the event and parse
> it.
> 
> Benjamin has added a marginal_path group(multipath marginal
> pathgroups) in
> the dm-multipath.
> https://patchwork.kernel.org/project/dm-devel/cover/1564763622-31752-1-git
> -send-email-bmarzins at redhat.com/
> 
> One of the intention of the Benjamin's patch (support for maginal
> path) is
> to support for the FPIN events we receive from fabric.
> On receiving the fpin-li our intention was to  place all the paths
> that
> are affected into the marginal path group.
> 

I'm aware of Ben's work, but I hadn't realized it had anything to do
with FPIN. As of today, multipathd doesn't listen on the
NETLINK_SCSITRANSPORT socket. Does any user space tool do this?
Google didn't show me anything.

Regards,
Martin

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