Re: net/sched: act_police: more accurate MTU policing

[Greg KH <gregkh@linuxfoundation.org>]

On Fri, Jun 10, 2022 at 07:08:48PM +0200, Davide Caratti wrote:
> hello Greg,
> 
> thanks for looking at this!
> 
> On Fri, Jun 10, 2022 at 05:09:21PM +0200, Greg KH wrote:
> > On Fri, Jun 10, 2022 at 04:58:37PM +0200, Davide Caratti wrote:
> > > hello,
> > > 
> > > Ilya reports bad TCP throughput when GSO packets hit an OVS rule that does
> > > tc MTU policing. According to his observations [1], the problem is fixed
> > > by upstream commit 4ddc844eb81d ("net/sched: act_police: more accurate MTU
> > > policing"). Can we queue this commit for inclusion in stable trees?
> > 
> > Did you test this,
> 
> I tested it on upstream, RHEL8 and RHEL9 kernels. BTW, the kselftest I included
> in the commit only verifies the correct setting for the MTU threshold, not
> the GSO problem (to test GSO, we should use netperf / iperf3 rather than
> mausezahn to generate traffic).
> 
> > and what kernel(s) do you want it applied to?
> 
> the reported bug is in act_police since the very beginning; however, the
> patch should apply cleanly at least on 5.x kernels. On older ones, there
> might be a small conflict due to lack of RCU-ification of struct
> tcf_police_params.
> A conflict that gets fixed easily, but in case we need it I volunteer to
> write a patch for kernels older than 4.20. @Ilya, what is the
> minimum kernel usable for openvswitch with MTU policing?
> 

It does not apply to 5.10 or earlier, so please provide a working
backport for those kernels if you wish it to be applied there.

thanks,

greg k-h