Thu, May 28, 2015 at 05:35:05PM CEST, john.fastab...@gmail.com wrote: >On 05/28/2015 02:42 AM, Jiri Pirko wrote: >>Mon, May 18, 2015 at 10:19:16PM CEST, da...@davemloft.net wrote: >>>From: Roopa Prabhu <ro...@cumulusnetworks.com> >>>Date: Sun, 17 May 2015 16:42:05 -0700 >>> >>>>On most systems where you can offload routes to hardware, >>>>doing routing in software is not an option (the cpu limitations >>>>make routing impossible in software). >>> >>>You absolutely do not get to determine this policy, none of us >>>do. >>> >>>What matters is that by default the damn switch device being there >>>is %100 transparent to the user. >>> >>>And the way to achieve that default is to do software routes as >>>a fallback. >>> >>>I am not going to entertain changes of this nature which fail >>>route loading by default just because we've exceeded a device's >>>HW capacity to offload. >>> >>>I thought I was _really_ clear about this at netdev 0.1 >> >>I certainly agree that by default, transparency 1:1 sw:hw mapping is >>what we need for fib. The current code is a good start! >> >>I see couple of issues regarding switchdev_fib_ipv4_abort: >>1) If user adds and entry, switchdev_fib_ipv4_add fails, abort is >> executed -> and, error returned. I would expect that route entry should >> be added in this case. The next attempt of adding the same entry will >> be successful. >> The current behaviour breaks the transparency you are reffering to. >>2) When switchdev_fib_ipv4_abort happens to be executed, the offload is >> disabled for good (until reboot). That is certainly not nice, alhough >> I understand that is the easiest solution for now. >> >>I believe that we all agree that the 1:1 transparency, although it is a >>default, may not be optimal for real-life usage. HW resources are >>limited and user does not know them. The danger of hitting _abort and >>screwing-up the whole system is huge, unacceptable. >> >>So here, there are couple of more or less simple things that I suggest to >>do in order to move a little bit forward: >>1) Introduce system-wide option to switch _abort to just plain fail. >> When HW does not have capacity, do not flush and fallback to sw, but >> rather just fail to add the entry. This would not break anything. >> Userspace has to be prepared that entry add could fail. >>2) Introduce a way to propagate resources to userspace. Driver knows about >> resources used/available/potentially_available. Switchdev infra could >> be extended in order to propagate the info to the user. > >I currently use the FlowAPI work I presented at netdev conference for >this. Perhaps I was a bit reaching by trying to also push it as a >replacement for the ethtool flow classification mechanism all in one >shot. For what it is worth replacing 'ethtool' flow classifier when >I have a pipeline of tables in a NIC is really my first use case for >the 'set' operations but that is off-topic probably. > >The benefits I see of using this interface (or if you want rename >it and push it into a different netlink type) is it gives you the entire >view of the switch resources and pipeline from a single interface. Also >because you are talking about system-wide behaviour above it nicely >rolls up into user space software where we can act on it with the >flags we have for l2 already and if we pursue your option (3) also l3. >I like the single interface vs. scattering the information across many >different interfaces this way we can do it once and be done with it. >If you scatter it across all the interfaces just l2,l3 for now but >we will get more then each interface will have its own mechanism and >I have no idea where you put global information such as table ordering.
I think that for fib capacities/capabilities, user should be able to use extended existing Netlink interface. Not some parallel one. I'm still not convinced that user should care about the actual hw pipeline. We already have a pipeline in kernel. Switch drivers should just do mapping, easy as that. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
