I checked that the filters cannot classify the traffic - 
all the traffics are enqueued to the default class, 
so they cannot allocate their bandwidth. 

I followed the cbq kernel source code line by line and here is a cbq_classify:
(see my comments between the lines)

// net/sched/sch_cbq.c (kernel version 2.4.19)

static struct cbq_class *
cbq_classify(struct sk_buff *skb, struct Qdisc *sch)
{
        struct cbq_sched_data *q = (struct cbq_sched_data*)sch->data;
        struct cbq_class *head = &q->link;
        struct cbq_class **defmap;
        struct cbq_class *cl = NULL;
        u32 prio = skb->priority;
        struct tcf_result res;

        /*
         *  Step 1. If skb->priority points to one of our classes, use it.
         */
        if      (TC_H_MAJ(prio^sch->handle) == 0 &&
                        (cl = cbq_class_lookup(q, prio)) != NULL)
                return cl;

        for (;;) {
                int result = 0;

                defmap = head->defaults;

                /*
                 * Step 2+n. Apply classifier.
                 */

<<my comment>> in 'tc_classify' function, if the traffic has an appropriate 
<<my comment>> filter, class is selected for the traffic. 
<<my comment>> Normally, appropriate classes are selected on the Pentium CPU, 
<<my comment>> but not on the MPC8250 (PowerPC based CPU) for the same traffic 
<<my comment>> and the same tc configuration, so 'goto fallback'
<<my comment>> I used u32 filter for packet classification : Is u32_classify
<<my comment>> function eventually called? 

                if (!head->filter_list 
                                || (result = tc_classify(skb, head->filter_list, &res)) < 0)
                        goto fallback;

                if ((cl = (void*)res.class) == NULL) {
                        if (TC_H_MAJ(res.classid))
                                cl = cbq_class_lookup(q, res.classid);
                        else if ((cl = defmap[res.classid&TC_PRIO_MAX]) == NULL)
                                cl = defmap[TC_PRIO_BESTEFFORT];

                        if (cl == NULL || cl->level >= head->level)
                                goto fallback;
                }

#ifdef CONFIG_NET_CLS_POLICE
                switch (result) {
                case TC_POLICE_RECLASSIFY:
                        return cbq_reclassify(skb, cl);
                case TC_POLICE_SHOT:
                        return NULL;
                default:
                        break;
                }
#endif

<<my comment>> if the traffic founds its filters, 
<<my comment>> class is returned at this point (on the Pentium CPU). 

                if (cl->level == 0)
                        return cl;

                /*
                 * Step 3+n. If classifier selected a link sharing class,
                 *     apply agency specific classifier.
                 *     Repeat this procdure until we hit a leaf node.
                 */
                head = cl;
        }

fallback:
        cl = head;

        /*
         * Step 4. No success...
         */
        if (TC_H_MAJ(prio) == 0 &&
                        !(cl = head->defaults[prio&TC_PRIO_MAX]) &&
                        !(cl = head->defaults[TC_PRIO_BESTEFFORT]))
                return head;

        return cl;
}

but one thing strange is when I check the filter list with the command 
'tc filter show dev eth0' nothing wrong in the filter lists. 

Any Idea or recommendation for more investigation?