jneiberger at gmail
Aug 17, 2012, 6:48 AM
Post #4 of 8
Thanks, I suspected that was the case or it would have been mentioned
Re: Increasing hold-queue to alleviate microbursts with small hardware queues
[In reply to]
before. We have played around with different queuing parameters and queue
depths, but I'm trying to find some other potential solutions.
Would a shaping service policy work for this? I'm wondering what the impact
would be on microbursts if we enabled shaping. Would that give us any
additional short-term buffer space?
On Aug 17, 2012 2:44 AM, "Phil Mayers" <p.mayers [at] imperial> wrote:
> On 08/17/2012 07:02 AM, John Neiberger wrote:
>> This has come up a few times recently. We continue to run into new
>> situations where we see lots of output queue drops on 6748 blades,
>> especially in cases where a 10g link is feeding a 1g link. We see OQDs
>> long before the interface approaches anything close to line rate on
> As I'm sure you're aware, but just for the archives, average rate is
> pretty irrelevant in this scenario. All that matters is the burst rate at
> the ingress (10 gig) port.
> 6748 cards have ~1.3Mb of per-port output buffer, which at 9Gbit/sec (10
> in minus 1 out) will fill in ~1.1 milliseconds. At some fraction of that
> load (e.g. 5 in, 1 out) it'll scale appropriately.
> If you are doing QoS with the default queue parameters, you'll get
> (possibly much) less than that.
> bursty traffic. Is it possible that the solution to this particular
>> problem is this simple?
> As others have said, no. It won't do anything.
> You're sure you've either disabled QoS or reconfigured the queues to
> allocate space appropriately i.e. in proportion to the offered load?
> TBH microburst problems on this platform don't come up on the list very
> often, as far as I can see. It's usually the lower-end catalysts.
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