[LARTC] RED problem !

[ahu@xxxxxxx (bert hubert)]

On Tue, Jan 01, 2002 at 10:33:06PM +0530, Arindam Haldar wrote:
> hi  all,
> 
> while trying red inplace of sfq/pfifo i go the follwing error
> 
> tc qdisc add dev eth0 parent 1:470 red max 12288 min 6100 limit 12288 
> avpkt 1514 burst 2

This returns -1:

int tc_red_eval_ewma(unsigned qmin, unsigned burst, unsigned avpkt)
{
        int wlog = 1;
        double W = 0.5;
        double a = (double)burst + 1 - (double)qmin/avpkt;

        if (a < 1.0)
                return -1;
        for (wlog=1; wlog<32; wlog++, W /= 2) {
                if (a <= (1 - pow(1-W, burst))/W)
                        return wlog;
        }
        return -1;
}


You can use this to calculate what is wrong. Either burst+1-qmin/avpkt is
smaller than 1, or a is too high to be matched by a time constant.

Regards,

bert

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