netdev - Re: [PATCH] tcp_cubic: limit delayed_ack ratio to prevent divide error

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Message-ID: <alpine.WNT.2.00.1105041352020.6048@JBRANDEB-DESK2.amr.corp.intel.com>
Date:	Wed, 4 May 2011 13:53:51 -0700 (Pacific Daylight Time)
From:	"Brandeburg, Jesse" <jesse.brandeburg@...el.com>
To:	Stephen Hemminger <shemminger@...tta.com>
cc:	David Miller <davem@...emloft.net>,
	Sangtae Ha <sangtae.ha@...il.com>,
	Injong Rhee <injongrhee@...il.com>,
	"Valdis.Kletnieks@...edu" <Valdis.Kletnieks@...edu>,
	"rdunlap@...otime.net" <rdunlap@...otime.net>,
	"lkml@...hboom.com" <lkml@...hboom.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tcp_cubic: limit delayed_ack ratio to prevent divide
 error



On Wed, 4 May 2011, Stephen Hemminger wrote:

> TCP Cubic keeps a metric that estimates the amount of delayed
> acknowledgements to use in adjusting the window. If an abnormally
> large number of packets are acknowledged at once, then the update
> could wrap and reach zero. This kind of ACK could only
> happen when there was a large window and huge number of
> ACK's were lost.
> 
> This patch limits the value of delayed ack ratio. The choice of 32
> is just a conservative value since normally it should be range of 
> 1 to 4 packets.
> 
> Signed-off-by: Stephen Hemminger <shemminger@...tta.com>

patch seems fine, but please credit the reporter (lkml@...hboom.com) with 
reporting the issue with logs, maybe even with Reported-by: and some kind 
of reference to the panic message or the email thread in the text or 
header?

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