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List:       openvswitch-discuss
Subject:    [ovs-discuss] Inaccurate statistics in flow_removed struct using OpenvSwitch
From:       blp () nicira ! com (Ben Pfaff)
Date:       2011-05-18 22:24:56
Message-ID: 20110518222456.GX15092 () nicira ! com
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It's busted again due to the merge from next.  I have a patch out to
fix it again, though.  (I haven't tested the accuracy, though.)

On Wed, May 18, 2011 at 03:22:51PM -0700, kk yap wrote:
> Hi,
> 
> Thanks for the very fast response.  TY tested the code and it worked.
> 
> Regards
> KK
> 
> On 18 May 2011 12:55, Ethan Jackson <ethan at nicira.com> wrote:
> >> Looking at the code, ovs-openflowd returns facet + stat as packet
> >> count for the flow removed. ?The number recorded by facet is correct,
> >> but the sum of the value exceed the real value. ?This occurs at the
> >> facet_update_stats function. ?What is the purpose of the addition?
> >> Can we expect accurate statistics from OVS?
> >
> > I should have responded to this question in my previous email. ?Packet
> > statistics are recorded in a best-effort fashion. ?In general they
> > should be accurate, but there is no hard guarantee that they are
> > especially in certain edge cases involving complex flow tables
> > including resubmit actions. ?In short, you should expect accurate
> > statistics from OVS noting the aforementioned caveat.
> >
> > Thanks again for reporting this bug.
> > Ethan
> >
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