Or, On Oct 26, 2011, at 5:48 AM, Or Gerlitz wrote:
> Rustad, Mark D <[email protected]<mailto:[email protected]>> > wrote: > >> Mike, Just to make sure I understand the context, DCB vlan ID + pbits >> and a like setting is targeted for iscsi HW offloads, correct? > > It really isn't targeted for iscsi HW offloads. In fact I don't think there > is any connection at all. It is about honoring the iscsi application priority > established by DCB, whether offloaded or not. > > Mark (added the list), > > When you say "iscsi application priority" does this eventually should result > in the 8021q priority bits set for iscsi sessions > or its priority in some other/higher level which relates to DCB/ETS? It is referring to setting the 8021q VLAN tag priority bits according to the iscsi priority indicated in the app TLV. This priority not only goes into the tag, but also affects the egress queuing priority, which of course also relates to ETS and PFC. > The lldpad daemon processes the LLDP protocol to negotiate DCB settings. It > then communicates the settings down to the drivers, which expose them via > netlink. iscsid accesses that information via netlink to establish a priority > setting when iscsi sessions are created. > > When you say "drivers" I assume you refer to the network/ethernet drivers, > correct? Yes, the underlying ethernet drivers. > As you can see from the description above, the iscsi kernel code plays no > role in setting or controlling the priority. Right now it is all done by > iscsid based on information that it receives from the kernel. > > So in high level, how iscsid acts to form that priority for the iscsi > session? is it through invoking some setsockopt (e.g SO_PRIORITY or IP_TOS) > before handing the iscsi tcp socket to the kernel? iscsid simply uses setsockopt with SO_PRIORITY to set the priority. The messy bit here is tracking down the network interface that the traffic is going through, since the DCB parameters could be different on different interfaces. > What sort of support are you looking for? > > I'm looking for a way to specify a vlan priority for an iSER (iSCSI RDMA) > session for the case of using iser in conjunction with IBoE (Infiniband over > Ethernet), unlike the case of iscsi/tcp, the iser session is established from > within the kernel under the directive of iscsid. What I can do is patch the > iscsi code to deliver trough the iscsi netlink user/kernel comm a priority > which it can get from the local 8021q device egress mapping or from DCB. Clearly things will be different for sessions established within the kernel. There is a DCB notifier that could be helpful, in that it could help you adapt to changes in priority over time, but you still need awareness of what interface the session is being routed through. Just so you know, DCB is already providing netlink multicast messages for DCB parameter changes when in IEEE mode, and more recently also in CEE mode. These messages contain the entire state of DCB for the interface, and so are pretty useful. -- Mark Rustad, LAN Access Division, Intel Corporation -- You received this message because you are subscribed to the Google Groups "open-iscsi" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/open-iscsi?hl=en.
