Full 32bit flowid from igb(4)

[Jack Vogel]

I think that line was there at one time outside the RSS define, I'd have to
take a look at
the code a bit more, or maybe Eric will....

Jack


On Mon, Mar 23, 2015 at 4:42 PM, hiren panchasara <
hiren at strugglingcoder.info> wrote:

> Correcting Eric's email and subject line.
>
> On 03/23/15 at 04:39P, hiren panchasara wrote:
> > scottl at freebsd.org
> > Bcc:
> > Subject: Full 32bit flowid from igb(4) [was: Re: Unbalanced LACP link]
> > Reply-To:
> > In-Reply-To: <20150319175145.GH53237 at strugglingcoder.info>
> >
> > On 03/19/15 at 10:51P, hiren panchasara wrote:
> > > On 03/17/15 at 12:34P, Adrian Chadd wrote:
> > > > On 17 March 2015 at 11:33, Jason Wolfe <nitroboost at gmail.com> wrote:
> > > > > On Mon, Mar 16, 2015 at 2:43 AM, Hans Petter Selasky <
> hps at selasky.org> wrote:
> > > > >> On 03/16/15 10:37, Vitalii Duk wrote:
> > > > >>>
> > > > >>> I've changed use_flowid to 0 and it helped! But isn't it setting
> > > > >>> significant? In a description it says "Shift flowid bits to
> prevent
> > > > >>> multiqueue collisions".
> > > > >>
> > > > >>
> > > > >> Hi,
> > > > >>
> > > > >> Maybe your ethernet hardware is not properly setting the m_flowid
> ...
> > > > >>
> > > > >> --HPS
> > > > >>
> > > > >
> > > > > Flip use_flowid back to 1 and try setting
> > > > > net.link.lagg.default_flowid_shift / net.link.lagg.X.flowid_shift
> to 0
> > > > > as Hiren suggested.  r260179 added this shift, which has caused us
> > > > > balancing issues with the i350/igb.
> > > > >
> > > > > https://svnweb.freebsd.org/base?view=revision&revision=260179
> > > > >
> > > > > Based on Adrian's comment about igb/ixgbe not setting the 'full
> > > > > flowid' under normal conditions, does that mean this shift should
> be 0
> > > > > by default to ensure we don't break balancing for devices that only
> > > > > set the CPU/MSIX queue?
> > > >
> > > > Or we can just see if there's anything wrong with putting the full 32
> > > > bit RSS flowid in received packets that have them.
> > >
> > > It'd be nice to have but for now I am proposing following to fix a
> known
> > > broken case because of an optimization:
> > > https://reviews.freebsd.org/D2098
> >
> > Turns out, setting flowid_shift to 0 is not the correct solution. Please
> > look at the review above for more details.
> >
> > Looking at the code, we have a way to get full flowid but it's hidden
> > under "ifdef RSS":
> >     rxr->fmp->m_pkthdr.flowid = le32toh(cur->wb.lower.hi_dword.rss);
> >
> > Using just this line gives me good hash on I350 igb(4) chipset that we
> > have.
> >
> > Is it possible to expose this outside RSS? Would this break other
> > things/chips?
> >
> > Cheers,
> > Hiren
>
>