netdev - Re: using software TSO on non-TSO capable netdevices

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Date:	Thu, 31 Jul 2008 10:29:24 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	buytenh@...tstofly.org (Lennert Buytenhek)
Cc:	davem@...emloft.net, netdev@...r.kernel.org, akarkare@...vell.com,
	nico@....org
Subject: Re: using software TSO on non-TSO capable netdevices

Lennert Buytenhek <buytenh@...tstofly.org> wrote:
>
> Index: linux-2.6.27-rc1/net/ipv4/tcp_output.c
> ===================================================================
> --- linux-2.6.27-rc1.orig/net/ipv4/tcp_output.c
> +++ linux-2.6.27-rc1/net/ipv4/tcp_output.c
> @@ -1544,7 +1544,7 @@ static int tcp_write_xmit(struct sock *s
>                        break;
> 
>                if (tso_segs == 1) {
> -                       if (unlikely(!tcp_nagle_test(tp, skb, mss_now,
> +                       if (unlikely(!tcp_nagle_test(tp, skb, 5 * mss_now,
>                                                     (tcp_skb_is_last(sk, skb) ?
>                                                      nonagle : TCP_NAGLE_PUSH))))
>                                break;

What's the size of your application's write calls?

But yeah we should at least offer something like this patch (with
5 * mss_now replaced by the TSO aggregation limit) as an option in
addition to nalge itself for those apps that do small writes.

Cheers,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
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