Thomas Graf wrote:
* Mark Seger <[EMAIL PROTECTED]> 2007-12-18 08:37
Anyhow, I just wanted to let people know that ALL tools that monitor
once a second on older counters will get the wrong numbers and tools
that correct for the wrong number by using fractional intervals (and I
suspect mine is the only one that does) but run on newer kernels will
also get the wrong numbers. In any event, if anyone is interested in
trying out collectl - it monitors a LOT more than just networks - you
can snag a copy of from http://collectl.sourceforge.net/ if you'd like
to take if for a drive. The website has a lot of output examples to
give you a better idea what it can do. I even included a writeup about
the odd network performance observations at
http://collectl.sourceforge.net/NetworkStats.html
I've solved this problem by using netlink to read the interface counters
ten times per second and maintain an own counter from which I calculate
the rate exactly once per second/minute/hour. The rate per second may
still be inaccurate to some degree, therefore I keep a history of 2-5
rates and take them into account to smoothen the result. This works
fairly well with _all_ operating systems.
I guess I'm not entirely sure what you're saying with respect to 10
times/sec. Is this once very .1 secs or 10 times in rapid fire? From a
general purpose monitoring perspective, since I read hundreds of
counters every second doing it 10 times/sec is way too much overhead and
special processing for netowork counters would also be pretty painful.
The general problem of the counters only changing once a second means
you'll never do that well when you monitor close the the interval and
you can't ever get accurate counters at lower rates. In fact, if you
try to treat the network counters like any other and if you monitor say
every .2 seconds, you see a rate of 0 for 4 of the 5 intervals and
500MB/sec for the 5th.
-mark
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