On Wed, Nov 09, 2011 at 08:14:36PM -0800, Ben Pfaff wrote: > On Thu, Nov 10, 2011 at 10:20:24AM +0900, Simon Horman wrote: > > On Wed, Nov 09, 2011 at 01:19:42PM -0800, Ben Pfaff wrote: > > > On Mon, Nov 07, 2011 at 04:20:19PM +0900, Simon Horman wrote: > > > > Although a very simple and possibly na??ve approach, I wonder if > > > > dynamically extending the interval at which statistics are collected is > > > > a worthwhile approach to mitigating the performance impact of statistics > > > > collection. > > > > > > It's one approach. It has the nice property of being very simple. > > > > > > Another approach that I've been pondering myself is, when there are many > > > datapath flows, to read out the kernel stats for only some of them at a > > > time and apply the expiration algorithm to just those. We could run > > > expiration just as frequently overall, but it would apply to any given > > > flow less frequently. > > > > I had also considered that and I think it an approach worth investigating. > > It seems to me that the main challenge will be arrange things such that a > > partial statistics update can occur while still allowing all statistics to > > be updated over time. I wonder if partitioning the flow hash would be a > > reasonable way to achieve this. > > I think that it works OK already. Just start the flow dump and read as > many flows as you want to deal with at a time, then stop, keeping the > dump in progress. Then when you want to keep going later, just keep > reading the dump.
Good point. I'll see about testing that. > I'd have to go look for the exact behavior when the flow table resizes > (perhaps some flows would be lost or seen twice?), but I'm not sure that > those are a big deal. If flow table resizes only occur occasionally - which I believe is the case - then I don't think it should be too much of a big deal. _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev
