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Re: [Xen-devel] TSQ accounting skb->truesize degrades throughput for large packets

On 07/09/13 18:21, Eric Dumazet wrote:
On Fri, 2013-09-06 at 10:00 -0700, Eric Dumazet wrote:
On Fri, 2013-09-06 at 17:36 +0100, Zoltan Kiss wrote:

So I guess it would be good to revisit the default value of this

If ixgbe requires 3 TSO packets in TX ring to get line rate, you also
can tweak dev->gso_max_size from 65535 to 64000.

Another idea would be to no longer use tcp_limit_output_bytes but

max(sk_pacing_rate / 1000, 2*MSS)

I've tried this on a freshly updated upstream, and it solved my problem on ixgbe:

- if (atomic_read(&sk->sk_wmem_alloc) >= sysctl_tcp_limit_output_bytes) { + if (atomic_read(&sk->sk_wmem_alloc) >= max(sk->sk_pacing_rate / 1000, 2 * mss_now) ){

Now I can get proper line rate. Btw. I've tried to decrease dev->gso_max_size to 60K or 32K, both was ineffective.



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