netdev - Re: [PATCH] tcp: sndbuf autotuning improvements

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Message-Id: <20131002.164600.347083935801850982.davem@davemloft.net>
Date:	Wed, 02 Oct 2013 16:46:00 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	netdev@...r.kernel.org, ncardwell@...gle.com, ycheng@...gle.com,
	maze@...gle.com
Subject: Re: [PATCH] tcp: sndbuf autotuning improvements

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Tue, 01 Oct 2013 10:23:44 -0700

> From: Eric Dumazet <edumazet@...gle.com>
> 
> tcp_fixup_sndbuf() is underestimating initial send buffer requirements.
> 
> It was not noticed because big GSO packets were escaping the limitation,
> but with smaller TSO packets (or TSO/GSO/SG off), application hits
> sk_sndbuf before having a chance to fill enough packets in socket write
> queue.
> 
> - initial cwnd can be bigger than 10 for specific routes
> 
> - SKB_TRUESIZE() is a bit under real needs in some cases,
>   because of power-of-two rounding in kmalloc()
> 
> - Fast Recovery (RFC 5681 3.2) : Cubic needs 70% factor
> 
> - Extra cushion (application might react slowly to POLLOUT)
> 
> tcp_v4_conn_req_fastopen() needs to call tcp_init_metrics() before
> calling tcp_init_buffer_space()
> 
> Then we realize tcp_new_space() should call tcp_fixup_sndbuf()
> instead of duplicating this stuff.
> 
> Rename tcp_fixup_sndbuf() to tcp_sndbuf_expand() to be more
> descriptive.
> 
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Signed-off-by: Neal Cardwell <ncardwell@...gle.com>
> Signed-off-by: Yuchung Cheng <ycheng@...gle.com>
> Acked-by: Maciej Żenczykowski <maze@...gle.com>

I assume this is meant for net-next as that is where this applies
cleanly.

Applied, thanks.
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