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

[Hannes Reinecke]

On 3/31/21 1:45 PM, Martin Wilck wrote:
> 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.
> 
I did, once, but that was years ago.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		           Kernel Storage Architect
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