What's the status of parallel netisr?

[Kevin Oberman]

> Date: Thu, 18 Sep 2008 22:50:10 +0800
> From: "Jian Qiu" <swordqiu at gmail.com>
> Sender: owner-freebsd-net at freebsd.org
> 
> Thanks again for the info.
> 
> As you suggested, I did test on the most recent 7.0-stable-200807 kernel.
> 
> The SMP throughout on the new kernel was improved to around 90MB/s.
> 
> However, SMP kernel still had no advantage over UP, at least for this
> kind of single threaded applications.
> 
> I further did the same test on Linux with both SMP and UP.
> 
> I did observe the same trend.
> 
> The throughput on UP (~210MB/ecs) was also much better than SMP (~170MB/sec).
> 
> However, I was surprised again that the local UDP throughput on Linux
> was more than double of FreeBSD.
> 
> Since all these tests were performed on the same machine, it must be
> because of the kernel that made such big differences.
> 
> I'm curious what is the major performance bottleneck in FreeBSD network stack??
> 
> Is there any plan in community to address these issues?

Did you try locking down the CPUs used with cpuset (FreeBSD) or taskset
(Linux)? This can make a very substantial difference. Something like a
UDP canon will run far more efficiently if locked to a single CPU and
will run best if that CPU is not processing the interrupts.
-- 
R. Kevin Oberman, Network Engineer
Energy Sciences Network (ESnet)
Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab)
E-mail: oberman at es.net			Phone: +1 510 486-8634
Key fingerprint:059B 2DDF 031C 9BA3 14A4  EADA 927D EBB3 987B 3751
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