Thanks Patrick, disabling the ETH TSO helped, TBF is working okay now.
Thanks again,
~Basit
Patrick McHardy wrote:
David Miller wrote:
From: Abdul Basit <abasit@xxxxxxxxx>
Date: Tue, 14 Oct 2008 21:37:04 -0400
[ netdev CC:'d, you'll reach more knowledgable people there ]
I am running linux kernel 2.6.23.1 on PowerPC and trying to set
qdisc tbf to limit the rate:-
*
*==> tc qdisc add dev eth0 root tbf rate 2048kbit buffer 10kb
latency 50ms
The problem is no matter what rate i specify, if I download a file
it always get down to ~16-18Kbps download speed,
after investigating a bit more, i found by tc -s qdisc show that
many dropped packets show up in statistic s,
looking further in kernel code, I found that in
linux/net/sched/sch_tbf.c:126
static int tbf_enqueue(struct sk_buff *skb, struct Qdisc* sch)
{
struct tbf_sched_data *q = qdisc_priv(sch);
int ret;
if (skb->len > q->max_size) {
printk (KERN_INFO "tbf_enqueue, drop skb->len = %d,
q->max_size = %d\n", skb->len, q->max_size);
sch->qstats.drops++;
....
}
whenever it try to enqueue the packet, the skb->len ( range from
2980 - 2977 ) is usually greator than q->max_size ( 2907 )
hence it drops the packet.
On a different machine with same source code, skb->len never become
> 1500 and there the tbf works fine.
Could someone please provide more insight or help where should i
look more?
This appears to caused by TSO. Try disabling TSO using ethtool or
configure TBF to handle larger packet sizes.
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