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From: "Ananyev, Konstantin" <konstantin.ananyev@intel.com>
To: Matthew Hall <mhall@mhcomputing.net>, Vladislav Zolotarov
 <vladz@cloudius-systems.com>
Thread-Topic: [dpdk-dev] [PATCH v1] ixgbe_pmd: forbid tx_rs_thresh above 1
 for all NICs but 82598
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Date: Fri, 11 Sep 2015 17:42:48 +0000
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Subject: Re: [dpdk-dev] [PATCH v1] ixgbe_pmd: forbid tx_rs_thresh above 1
 for all NICs but 82598
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> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Matthew Hall
> Sent: Friday, September 11, 2015 6:18 PM
> To: Vladislav Zolotarov
> Cc: dev@dpdk.org
> Subject: Re: [dpdk-dev] [PATCH v1] ixgbe_pmd: forbid tx_rs_thresh above 1=
 for all NICs but 82598
>=20
> On Fri, Sep 11, 2015 at 07:18:20PM +0300, Vladislav Zolotarov wrote:
> > We thought about linearization too. It's doable with extra mempool and =
it
> > may be optional so that those that don't need could compile it out and/=
or
> > disable it in a runtime...
>=20
> High-level question. How realistic is sending a 40-segment frame in the f=
irst
> place? This whole thing seems kind of academic to me unless I missed
> something.
>=20
> I usually use 2K pktmbufs and I don't think this is an uncommon size. Mos=
t
> jumbo frame hardware only does 9.5KB max frame size or so.
>=20
> So I am having a hard time imagining how I'd end up with more than 10 seg=
ments
> as a worst-case scenario.

As I remember, with freebsd stack when TSO is on it was not unusual to see =
chains of ~30 segments.=20
That's over port with 'normal' mtu (1.5K).
Konstantin

>=20
> Matthew.