Subject: Re: [RFC net-next PATCH V1 0/9] net: fragmentation performance scalability on NUMA/SMP systems

From: Jesper Dangaard Brouer <[email-masked]>
Date: Mon, 26 Nov 2012 15:42:10 +0100

On Sun, 2012-11-25 at 08:11 -0800, Eric Dumazet wrote:
> On Sun, 2012-11-25 at 09:53 +0100, Jesper Dangaard Brouer wrote:
> 
> > Yes, for the default large 64k packets size, its just a "fake"
> > benchmark.  And notice with my fixes, we are even faster than the
> > none-frag/single-UDP packet case... but its because we are getting a
> > GSO/GRO effect.
> 
> Could you elaborate on this GSO/GRO effect ?

On the big system, I saw none-frag UDP (1472 bytes) throughput of:
  7356.57 + 7351.78 + 7330.60 + 7269.26 = 29308.21 Mbit/s

While with UDP fragments size 65507 bytes I saw:
  9228.75 + 9207.81 + 9615.83 + 9615.87 = 37668.26 Mbit/s

Fragmented UDP is faster by:
 37668.26 - 29308.21 = 8360.05 Mbit/s

The 65507 bytes UDP size is just a benchmark test, and have no real-life
relevance.  As performance starts to drop (below none-frag/normal case)
when the frag size is decreased, to more realistic sizes...

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Sr. Network Kernel Developer at Red Hat
  Author of http://www.iptv-analyzer.org
  LinkedIn: http://www.linkedin.com/in/brouer