[ovs-dev] [PATCH v8 1/1] Avoid dp_hash recirculation for balance-tcp bond selection mode

Ben Pfaff blp at ovn.org
Tue Dec 17 21:28:34 UTC 2019


On Tue, Dec 17, 2019 at 10:26:05PM +0100, Ilya Maximets wrote:
> On 17.12.2019 20:23, Ben Pfaff wrote:
> > Is there a reason to allow users to turn this off?  What is the downside
> > of enabling it?  Why is it disabled by default?  In general, OVS should
> > optimize itself to the extent it can rather than relying on a
> > knowledgeable user to tweak it.  If it's necessary to make it
> > configurable, then the documentation (in vswitch.xml) should explain why
> > one would want to turn it on or off and what the default is.
> 
> Hi Ben,
> I just wanted to add a few comments here.  There are few possibly unwanted
> things that appears while enabling the feature:
> 1. Bonding rebalancing triggers reload of PMD threads, that might affect
>    performance of highly loaded threads.
> 2. While datapath supports lb_output action, netdev-offload provider might
>    not support it.  This could be an issue.
> So, I think it's sane to have a configuration knob.  Not sure about disabling
> by default but it might make a bit of sense keeping this feature as experimental
> for some time.  And yes, I agree  that documentation should be updated.

I didn't understand either of those points.  With those points, it makes
sense for it to be user configurable (and the documentation should be
clear about the tradeoffs).


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