Thu, May 28, 2015 at 05:40:11PM CEST, sfel...@gmail.com wrote: >On Thu, May 28, 2015 at 2:42 AM, Jiri Pirko <j...@resnulli.us> 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. >> 3) Introduce couple of flags for entry add that would alter the default >> behaviour. Something like: >> NLM_F_SKIP_KERNEL >> NLM_F_SKIP_OFFLOAD >> Again, this does not break the current users. On the other hand, this >> gives new users a leverage to instruct kernel where the entry should >> be added to (or not added to). >> >> Any thoughts? Objections? > >I don't like these. Breaks transparency and forces the user in a >position of having to know hardware failures modes (unique to each
Can you please elaborate on this a bit more? I fail to see transparency breaking in my proposal :/ Maybe it is by different understanding of the term? Also I do not understand the remark about user having to know hardware failure modes. Could you please explain? >hardware device). I presented an option d) which avoids this issues; >was it not understood? I just commented on option d) it other email. -- 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
