On Mon, Nov 28, 2011 at 02:03:10PM -0800, Ben Pfaff wrote: > On Thu, Nov 10, 2011 at 09:14:50AM -0800, Ben Pfaff wrote: > > On Thu, Nov 10, 2011 at 06:04:07PM +0900, Simon Horman wrote: > > > 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. > > > > Great, I look forward to hearing how well it works. > > Did you get a chance to experiment with this? I really am interested > in doing it this way, if it is effective.
Hi Ben, sorry for the long delay. I finally had a stab at implementing this idea but as yet it does not seem to be working. My implementation simply keeps track of a static struct dpif_flow_dump dump in update_stats() and resets it as necessary using dpif_flow_dump_start() and dpif_flow_dump_done(). The result seems to be that flows are expiring all over the place. I assume this is because their stats are not being updated. Do I need to keep track of more state in order to take into account that the flow_table is changing between calls to update_stats()? _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev
