Full 32bit flowid from igb(4)

[hiren panchasara]

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

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