[c-nsp] Dynamic output buffer allocation on Cisco 4948

[Terebizh, Evgeny]

Try also 
"show platform hardware interface gigabitEthernet 1/1 tx-queue".
I guess it's gonna show the actual values for queue utilisation.
Please let me know if this helps.

/ET




On 9/24/13 11:17 PM, "John Neiberger" <jneiberger at gmail.com> wrote:

>I've been helping to troubleshoot an interesting problem with variable
>latency through a 4948. I haven't run into this before. I usually have
>seen
>really low latency through 4948s, but this particular application requires
>consistent low latency and they've been noticing that latency goes up on
>average as load goes up. It didn't seem to be a problem on their servers,
>but communication through busy interfaces seemed to dramatically increase
>the latency. They were used to <1ms latency and it was bouncing up to 20+
>ms at times. I'm starting to think this is due to the shared output buffer
>in the 4948 causing the output buffer on the uplink to dynamically get
>bigger.
>
>I've been trying to find more details on how the 4948 handles its shared
>output queue space, but I haven't been able to find anything. Do any of
>you
>know more about how this works and what commands I could use to
>troubleshoot? I can't find anything that might show how much buffer space
>a
>particular interface is using at any given time, or if it even makes sense
>to think of it that way. If I knew the size of the buffer at any given
>moment, I could calculate the expected latency and prove whether or not
>that was the problem.
>
>Thanks!
>John
>_______________________________________________
>cisco-nsp mailing list  cisco-nsp at puck.nether.net
>https://puck.nether.net/mailman/listinfo/cisco-nsp
>archive at http://puck.nether.net/pipermail/cisco-nsp/