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

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Date:	Fri, 06 May 2011 12:15:46 -0400
From:	TB <lkml@...hboom.com>
To:	"Brandeburg, Jesse" <jesse.brandeburg@...el.com>
CC:	Stephen Hemminger <shemminger@...tta.com>,
	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>,
	"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

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On 11-05-04 04:53 PM, Brandeburg, Jesse wrote:
> 
> 
> 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?

We're currently testing the patch on 6 production servers

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