RFC: How to fix the NFS/iSCSI vs TSO problem

[Rick Macklem]

Marcelo Araujo wrote:
> Hello All,
> 
> 
> 2014-03-27 8:27 GMT+08:00 Rick Macklem <rmacklem at uoguelph.ca>:
> >
> > Well, bumping it from 32->35 is all it would take for NFS (can't
> > comment
> > w.r.t. iSCSI). ixgbe uses 100 for the 82598 chip and 32 for the
> > 82599
> > (just so others aren't confused by the above comment). I understand
> > your point was w.r.t. using 100 without blowing the kernel stack,
> > but
> > since the testers have been using "ix" with the 82599 chip which is
> > limited to 32 transmit segments...
> >
> > However, please increase any you know can be safely done from
> > 32->35, rick
> >
> >
> I have plenty of machines using Intel X540 that is based on 82599
> chipset.
> I have applied Rick's patch on ixgbe to check if the packet size is
> bigger
> than 65535 or cluster is bigger than 32. So far till now, on FreeBSD
> 9.1-RELEASE this problem does not happens.
> 
> Unfortunately all my environment here is based on 9.1-RELEASE, with
> some
> merges from 10-RELEASE such like: NFS and IXGBE.
> 
> Also I have applied the patch that Rick sent in another email with
> the
> subject 'NFS patch to use pagesize mbuf clusters'. And we can see
> some
> performance boost over 10Gbps Intel. However here at the company, we
> are
> still doing benchmarks. If someone wants to have my benchmark result,
> I can
> send it later.
> 
> I'm wondering, if this update on ixgbe from 32->35 could be applied
> also
> for versions < 9.2. I'm thinking, that this problem arise only on
> 9-STABLE
> and consequently on 9.2-RELEASE. And fortunately or not 9.1-RELEASE
> doesn't
> share it.
> 
My understanding is that the 32 limitation is a hardware one for the
82599. It appears that other drivers than the ixgbe.c can be increased
from 32->35, but not ixgbe.c (for the 82599 chips).

rick

> Best Regards,
> --
> Marcelo Araujo
> araujo at FreeBSD.org
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