[ovs-dev] [PATCH] ovn-controller: Provide the option to set Encap.options:csum
russell at ovn.org
Mon Jan 16 14:28:28 UTC 2017
On Sat, Jan 14, 2017 at 11:29 AM, Ben Pfaff <blp at ovn.org> wrote:
> On Sat, Jan 14, 2017 at 07:37:53PM +0530, Numan Siddique wrote:
> > On Sat, Jan 14, 2017 at 3:18 AM, Ben Pfaff <blp at ovn.org> wrote:
> > > On Tue, Jan 10, 2017 at 11:34:42AM +0530, Numan Siddique wrote:
> > > > ovn-controller by default enables UDP checksums for geneve
> > > > tunnels. With this patch user can set the desired value in
> > > > Open_vSwitch.external_ids:ovn_encap_csum.
> > > >
> > > > Signed-off-by: Numan Siddique <nusiddiq at redhat.com>
> > >
> > > I don't see technical problems with this, but I also don't know why a
> > > user would want to disable checksums. Can you send a v2 that adds this
> > > rationale to the documentation and to the commit message?
> > >
> > Thanks for the review. Sure I will do that. The reason for this patch is
> > we are seeing significant performance increase (more than 100%) in our
> > testing when tunnel checksum is disabled.
> > The lab servers have nics with geneve offload support (
> > tx-udp_tnl-segmentation
> > )
> > .
> OK, that sounds like a good reason to document.
In particular, it looks like the NICs we have, Intel X710, will do TCP
Segmentation Offload (TSO) with geneve or vxlan, but only if udp checksums
are turned off. Once they're on, TCP throughput gets cut to less than half.
This is going to be painful to document well if it's hardware dependent.
I'm not sure what the better default is, since checksums should actually
improve performance for NICs without geneve offload support.
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