[dpdk-dev] Performance regression in DPDK 1.8/2.0

[Pavel Odintsov]

Hello!

I executed deep test of Paul's toolkit and could approve performance
degradation in 2.0.0.

On Sun, Apr 26, 2015 at 9:50 PM, Paul Emmerich <emmericp at net.in.tum.de> wrote:
> Hi,
>
> I'm working on a DPDK-based packet generator [1] and I recently tried to
> upgrade from DPDK 1.7.1 to 2.0.0.
> However, I noticed that DPDK 1.7.1 is about 25% faster than 2.0.0 for my use
> case.
>
> So I ran some basic performance tests on the l2fwd example with DPDK 1.7.1,
> 1.8.0 and 2.0.0.
> I used an Intel Xeon E5-2620 v3 CPU clocked down to 1.2 GHz in order to
> ensure that the CPU and not the network bandwidth is the bottleneck.
> I configured l2fwd to forward between two interfaces of an X540 NIC using
> only a single CPU core (-q2) and measured the following throughput under
> full bidirectional load:
>
>
> Version  TP [Mpps] Cycles/Pkt
> 1.7.1    18.84     84.925690021
> 1.8.0    16.78     95.351609058
> 2.0.0    16.40     97.56097561
>
> DPDK 1.7.1 is about 15% faster in this scenario. The obvious suspect is the
> new mbuf structure introduced in DPDK 1.8, so I profiled L1 cache misses:
>
> Version   L1 miss ratio
> 1.7.1     6.5%
> 1.8.0    13.8%
> 2.0.0    13.4%
>
>
> FWIW the performance results with my packet generator on the same 1.2 GHz
> CPU core are:
>
> Version  TP [Mpps]  L1 cache miss ratio
> 1.7      11.77      4.3%
> 2.0      9.5        8.4%
>
>
> The discussion about the original patch [2] which introduced the new mbuf
> structure addresses this potential performance degradation and mentions that
> it is somehow mitigated.
> It even claims a 20% *increase* in performance in a specific scenario.
> However, that doesn't seem to be the case for both l2fwd and my packet
> generator.
>
> Any ideas how to fix this? A 25% loss in throughput prevents me from
> upgrading to DPDK 2.0.0. I need the new lcore features and the 40 GBit
> driver updates, so I can't stay on 1.7.1 forever.
>
> Paul
>
>
> [1] https://github.com/emmericp/MoonGen
> [2] http://comments.gmane.org/gmane.comp.networking.dpdk.devel/5155



-- 
Sincerely yours, Pavel Odintsov