Questions about the rate estimator: ip_vs_est.c

[Roberto Nibali <ratz@xxxxxxxxxxxx>]

Hi Wensong,

I see that the rate estimator currently is not used anywhere. From what 
I understand it tries to give you a means to provide 1/s information on 
packets, bytes and connections.
I wonder why it is done in such a complicated way? I know most of it is 
from the net/sched/estimator.c but why not using the direct way of 
computing the average?
Something like following should work:

avg = ((time - timeframe) * avg + new) / time

I've written a 2 minutes POC shell script that shows what I mean:

------------------------------------------------------------------
#!/bin/bash
# extremely stupid programme to show calculation of constant average

declare -i num=0
declare -i cnt=0
declare -i timeframe=2
declare avg=0

while read -p "Enter number: " num rest; do
        if [ "${rest}" == "q" ]; then
                exit
        fi

        cnt=$((${cnt}+${timeframe}))
        avg=$(echo "((${cnt}-${timeframe})*${avg}+${num})/${cnt}" | bc -l)
        printf "Average [cnt=%d]: %0.4f\n" "${cnt}" "${avg}"
done
------------------------------------------------------------------

Why are the numbers scaled by 2^5?

Would it make sense to use the ip_vs_estimator to write a scheduler 
which chooses the RS with either the least amount of bps or the least 
amount of pps?
I take it that the slow timer stuff is eliminated by now? :)

Best regards,
Roberto Nibali, ratz
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