Wed, Nov 02, 2016 at 03:13:42AM CET, ro...@cumulusnetworks.com wrote: >On 11/1/16, 10:03 AM, Ido Schimmel wrote: >> Hi Roopa, >> >> On Tue, Nov 01, 2016 at 08:14:14AM -0700, Roopa Prabhu wrote: >>> >[snip] >>> I have the same concern as Eric here. >>> >>> I understand why you need it, but can the driver request for an initial >>> dump and that >>> dump be made more efficient somehow ie not hold rtnl for the whole dump ?. >>> instead of making the fib notifier registration code doing it. >> We can do what we suggested in the last bi-weekly meeting, which is >> still holding rtnl, but moving the hardware operation to delayed work. >> This is possible because upper layers always assume operation was >> successful and driver is responsible for invoking its abort mechanism in >> case of failure. >> >>> these routing table sizes can be huge and an analogy for this in user-space: >>> We do request a netlink dump of routing tables at initialization (on >>> driver starts or resets)... >>> but, existing netlink routing table dumps for that scale don't hold rtnl >>> for the whole dump. >>> The dump is split into multiple responses to the user and hence it does not >>> starve other rtnl users. >> In my reply to Eric I mentioned that when we register and unregister >> from this chain the tables aren't really huge, but instead quite small. >> I understand your concerns, but I don't wish to make things more >> complicated than they should be only to address concerns that aren't >> really realistic. > >I understand..but, if you are adding some core infrastructure for switchdev >..it cannot be >based on the number of simple use-cases or data you have today. > >I won't be surprised if tomorrow other switch drivers have a case where they >need to >reset the hw routing table state and reprogram all routes again. >Re-registering the notifier to just >get the routing state of the kernel will not scale. For the long term, since >the driver does not maintain a cache,
Driver (mlxsw, rocker) maintain a cache. So I'm not sure why you say otherwise. >a pull api with efficient use of rtnl will be useful for other such cases as >well. How do you imagine this "pull API" should look like? > > >If you don't want to get to the complexity of a new api right away because of >the >simple case of management interface routes you have, Can your driver register >the notifier early ? >(I am sure you have probably already thought about this) Register early? What it would resolve? I must be missing something. We register as early as possible. But the thing is, we cannot register in a past. And that is what this patch resolves. > >> >> I believe current patch is quite simple and also consistent with other >> notification chains in the kernel, such as the netdevice, where rtnl is >> held during replay of events. >> http://lxr.free-electrons.com/source/net/core/dev.c#L1535 >as you know, netdev and routing scale are not the same thing. >Looking at the current code for netdevices (replay and rollback on failure), >a pull api (equivalent to the netlink dump api) may end up being less >complex...with an >ability to batch in the future. > > > > > > >
