Re: [dpdk-dev] [PATCH 0/9] mbuf: structure reorganization

[Olivier MATZ <olivier.matz@6wind.com>]

On Mon, 03 Apr 2017 18:15:25 +0200
Thomas Monjalon <thomas.monjalon@6wind.com> wrote:

> 2017-03-31 09:18, Ananyev, Konstantin:
> > > On Fri, 31 Mar 2017 09:41:39 +0100, Bruce Richardson
> > > <bruce.richardson@intel.com> wrote:  
> > > > On Fri, Mar 31, 2017 at 10:26:10AM +0200, Olivier Matz wrote:  
> > > > > I replayed my tests, and I can also see a performance loss
> > > > > with 1c/1t (ixgbe), not in the same magnitude however. Here
> > > > > is what I have in MPPS:
> > > > >
> > > > > 1c/1t   1c/2t
> > > > > 53.3    58.7     current
> > > > > 52.1    58.8     original patchset
> > > > > 53.3    58.8     removed patches 3 and 9
> > > > > 53.1    58.7     with konstantin's patch
> > > > >
> > > > > So we have 2 options here:
> > > > >
> > > > > 1/ integrate Konstantin's patch in the patchset (thank you,
> > > > > by the way) 2/ remove patch 3, and keep it for later until we
> > > > > have something that really no impact
> > > > >
> > > > > I'd prefer 1/, knowing that the difference is really small in
> > > > > terms of cycles per packet.
> > > > >
> > > > >  
> > > > 1 is certainly the more attractive option. However, I think we
> > > > can afford to spend a little more time looking at this before
> > > > we decide. I'll try and check out the perf numbers I get with
> > > > i40e with Konstantin's patch today. We also need to double
> > > > check the other possible issues he reported in his other
> > > > emails. While I don't want this patchset held up for a long
> > > > time, I think an extra 24/48 hours is probably needed on it.
> > > >  
> > > 
> > > Yes, now that we have the "test momentum", try not to loose it ;)
> > > 
> > > I'm guilty to have missed the performance loss, but honnestly,
> > > I'm a bit sad that nobody tried to this patchset before (it
> > > is available for more than 2 months), knowing this is probably
> > > one of the most critical part of dpdk. I think we need to be
> > > better next time.
> > > 
> > > Anyway, thank you for your test and feedback now.  
> > 
> > I am also leaning towards option 1, but agree that some extra
> > testing first need to be done before making the final decision.
> > BTW, path #9 need to be removed anyway, even if will go for path #1.
> > Konstantin  
> 
> Please, can we have a conclusion now?

I think we sholuld go with proposition 1, I can resubmit an updated
patch today.

This rework is needed at least for metrics libraries.

To summarize the perf data we have:
- There is a small impact on Intel NICs (-0.4MPPS on ixgbe in iofwd
  mode according to Konstantin's test, which is less than 1%). I guess
  it can be optimized.
- On mlx5, there is a gain (+0.8MPPS).
- On sfc, there is also a gain.

Any comment?

Olivier