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. -- To unsubscribe from this list: send the line "unsubscribe linux-net" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
