TCP stack throughput

Scott Lystig Fritchie <>
Wed Jul 27 08:20:11 CEST 2005


I'm sorry, I don't have Javier's original message in my mailbox.

>>>>> "uw" == Ulf Wiger <> writes:

uw> Den 2005-07-19 19:39:12 skrev Javier París Fernández
uw> <>:
>> I observed several funny things. The time spent processing the
>> connections seems to go up exponentially, but it is not limited by
>> cpu, which was always under 50%. I don't know what is throttling
>> it.

Are you using Linux, and if yes, which Linux distribution are you
using?  I was very surprised to discover that the "top" program
distributed with Red Hat Advanced Server 3.0, when running on an Intel
CPU with Hyper-Threading enabled(*), will report that:

main()
{
	int i;

	for (;;) {
		i++;
	}
}

... will only consume 50% CPU time.

I don't know why "top"'s behavior is different for AS 3.0: I'm used to
"top" reporting 100% CPU consumption by a program like that,
regardless of how many CPUs the machine has.

-Scott

(*) I do not know if disabling HT makes a difference or not.



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