[ovs-dev] Statistics Collection Performance Impact

[Simon Horman]

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.

Hi Ben,

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.