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

Stephen Hemminger
2011-05-06T16:54:04Z

On Fri, 06 May 2011 12:15:46 -0400
TB <lkml@techboom.com> wrote:

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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@vyatta.com>
> >
> > patch seems fine, but please credit the reporter (lkml@techboom.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

Thank you, is there some regularity to the failures previously?