Hi, > -----Original Message----- > From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Pavel Odintsov > Sent: Monday, April 27, 2015 9:07 AM > To: Paul Emmerich > Cc: dev at dpdk.org > Subject: Re: [dpdk-dev] Performance regression in DPDK 1.8/2.0 > > 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%
Could you tell me how you got the L1 cache miss ratio? Perf? > > > > > > 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. Could you provide more information on how you run the l2fwd app, in order to try to reproduce the issue: - L2fwd Command line - L2fwd initialization (to check memory/CPU/NICs) Did you change the l2fwd app between versions? L2fwd uses simple rx on 1.7.1, whereas it uses vector rx on 2.0 (enable IXGBE_DEBUG_INIT to check it). Last question, I assume you use your traffic generator to get all those numbers. Which packet format/size did you use? Does your traffic generator take into account the Inter-packet gap? Thanks! Pablo > > > > Paul > > > > > > [1] https://github.com/emmericp/MoonGen > > [2] > http://comments.gmane.org/gmane.comp.networking.dpdk.devel/5155 > > > > -- > Sincerely yours, Pavel Odintsov
