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From: "Richardson, Bruce" <bruce.richardson@intel.com>
To: Jun Han <junhanece@gmail.com>, "dev@dpdk.org" <dev@dpdk.org>
Thread-Topic: [dpdk-dev] l2fwd/l3fwd performance drop of about 25% ?
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Date: Thu, 27 Feb 2014 09:36:37 +0000
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Subject: Re: [dpdk-dev] l2fwd/l3fwd performance drop of about 25% ?
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> Hi all,
>=20
> I have a quick question regarding the performance of DPDK l2fwd (Same
> problem with l3fwd). I am seeing that when we start multiple ports (e.g.,
> 12 ports), for 64 byte packets, the RX rate is only at around 11 Mpps per
> port, instead of 14.88 Mpps which is the line rate (with preablem+start o=
f
> delimeter + interframe gap). Do you know what could be the problem? I am
> describing my experiment setup below.

When using both ports on a dual-port 10G NIC, you cannot hit line rate on b=
oth ports with 64-byte packets due to a lack of PCI bandwidth (for PCI Gen2=
 x8). If you try with two ports on different NICs you should be getting bet=
ter performance, as traffic for small packets for a single port at  10G can=
 be handled by the PCI slot. With larger packet sizes, e.g. 128 byte packet=
s, the issue also goes away and the NICs can manage full line rate.