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

[Zoltan Kiss <zoltan.kiss@xxxxxxxxxx>]

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
> > > setting.
> > 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.
Regards,

Zoli

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