[ovs-dev] [PATCH 08/11] metaflow: Extend size of mf_value to 128 bytes.

[Jesse Gross]

On Wed, Jul 1, 2015 at 2:20 AM, Loftus, Ciara <ciara.loftus at intel.com> wrote:
>> On Tue, Jun 30, 2015 at 7:56 AM, Loftus, Ciara <ciara.loftus at intel.com>
>> wrote:
>> >>
>> >> On Wed, Jun 24, 2015 at 1:17 PM, Ben Pfaff <blp at nicira.com> wrote:
>> >> > On Fri, Jun 19, 2015 at 04:13:22PM -0700, Jesse Gross wrote:
>> >> >> Tunnel metadata can be substantially larger than our existing fields
>> >> >> (up to 124 bytes in a single Geneve option) so this extends the size
>> >> >> of the data that we can handle with metaflow fields. This also
>> >> >> breaks a few tests that assume that their max size is also the
>> >> >> maximum that can be handled in a field.
>> >> >>
>> >> >> Signed-off-by: Jesse Gross <jesse at nicira.com>
>> >> >
>> >> > Did you look around at all to see whether this will unreasonably blow up
>> >> > any data or algorithms?
>> >>
>> >> I don't believe that it should have any significant effects.
>> >> Generally, code does operations on the fields based on mf->n_bytes
>> >> (with the exception of some memset()s here and there). I don't think
>> >> that we really store these in a large number for any real period of
>> >> time.
>> >
>> > With this series of patches, in particular patch 10/11 "tunnel: Geneve TLV
>> handling support for OpenFlow" I've measured a significant decrease in
>> performance with the dpdkport type. For example, with a loopback test with
>> 64Byte packets I've seen a 25% decrease in throughput.
>> > I suspect this is in relation to the size of the new tun_metadata struct. A
>> quick perf analysis and I see we're spending significantly more time initialising
>> packet metadata in the dp_netdev_process_rxq_port function.
>> > Are there any plans to address this performance degradation?
>>
>> Thanks for pointing that out. I just sent out a patch that should
>> hopefully avoid the problem of needing to initialize the newly
>> enlarged structure. I don't have a great way of doing performance
>> testing on it, would you mind seeing if it solves the problem you're
>> seeing?
>
> Hi Jesse, I've tested it and the new patch solves the problem I was seeing. Thanks for providing a fix so quickly!

Great! Thanks a lot for testing it.