On Fri, 25 May 2007, Stephen Clark wrote:
We have a network appliance that is currently based on 4.9. We are in the
process of releasing a new version based on 6.1 stable.
In our testing using nttcp thru the appliance we see insignifant difference
in thruput between the 2 versions in a controlled environment - aproximately
94mbs on a 100mb lan.
We have a person that is testing the both system inhouse surfing out over
the internet on our T1 link and he complains that he is consistently seeing
the 6.1 version being much slower than the 4.9 version (on the same
hardware). He has been comparing the 6.1 system to 4.9 system for a couple
of weeks and continues to insist the 6.1 version is much slower.
Are there any sysctl tunables that may affect performance going over the
internet with a slower link, dropped packets, etc that could cause this?
Any ideas would be appreciated.
Steve,
The first thing I'd do is try a double-blind test for your testers -- don't
tell them which version is running, and then compare performance complaints
with/without. This would let you know if there's actually a difference.
The main piece of advice I give people when working with 6.x is to consider
turning on net.isr.direct, which enables direct dispatch in the network stack.
With 4.x, I get lower forwarding and processing latency than 6.x unless I
enable this. However, my recollection is that you don't want to turn it on on
releases before 6.1, and I would really be most comfortable turning it on with
6.2 and later. In FreeBSD 7.0, net.isr.direct is the default.
You might give that a try and see if it has an effect, but I'd see about
getting some sort of objective testing of performance going to confirm that
this isn't a subjectivity issue.
Robert N M Watson
Computer Laboratory
University of Cambridge
Steve
--
"They that give up essential liberty to obtain temporary safety, deserve
neither liberty nor safety." (Ben Franklin)
"The course of history shows that as a government grows, liberty decreases."
(Thomas Jefferson)
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