netdev - Re: [PATCH net-next 2/2] tcp_cubic: refine Hystart delay threshold

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Date:	Thu, 4 Dec 2014 19:48:30 -0500
From:	Neal Cardwell <ncardwell@...gle.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	Nandita Dukkipati <nanditad@...gle.com>,
	Yuchung Cheng <ycheng@...gle.com>,
	Sangtae Ha <sangtae.ha@...il.com>
Subject: Re: [PATCH net-next 2/2] tcp_cubic: refine Hystart delay threshold

On Thu, Dec 4, 2014 at 7:13 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> From: Eric Dumazet <edumazet@...gle.com>
>
> In commit 2b4636a5f8ca ("tcp_cubic: make the delay threshold of HyStart
> less sensitive"), HYSTART_DELAY_MIN was changed to 4 ms.
>
> The remaining problem is that using delay_min + (delay_min/16) as the
> threshold is too sensitive.
>
> 6.25 % of variation is too small for rtt above 60 ms, which are not
> uncommon.
>
> Lets use 12.5 % instead (delay_min + (delay_min/8))

Very nice, Eric!

Acked-by: Neal Cardwell <ncardwell@...gle.com>
Tested-by: Neal Cardwell <ncardwell@...gle.com>

neal
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