netdev - Re: [PATCH net-next] tcp: tcp_tso_autosize() minimum is one packet

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Message-ID: <20150527020129.GA20792@gondor.apana.org.au>
Date:	Wed, 27 May 2015 10:01:29 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	davem@...emloft.net, netdev@...r.kernel.org, ncardwell@...gle.com
Subject: Re: [PATCH net-next] tcp: tcp_tso_autosize() minimum is one packet

On Wed, May 27, 2015 at 09:38:40AM +0800, Herbert Xu wrote:
> 
> Not really.  They're not identical.  For example, before your
> patch a packet greater than MSS with TSO disabled would call
> tcp_nagle_test, with your patch it will call tcp_tso_should_defer
> instead.
> 
> Maybe this is OK but it is far from obvious.

Funny enough it was you who originally introduced this change
in behaviour:

commit 8f26fb1c1ed81c33f5d87c5936f4d9d1b4118918
Author: Eric Dumazet <edumazet@...gle.com>
Date:   Tue Oct 15 12:24:54 2013 -0700

    tcp: remove the sk_can_gso() check from tcp_set_skb_tso_segs()

Now you're trying to do it again :)

The problem is back at the very beginning, tso_segs > 1 was the
same as TSO enabled.  So we either need to restore this identity
or find a new way of indiciating that TSO is enabled.

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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