On 06/19/2014 04:59 PM, Frank Ch. Eigler wrote:
> William Cohen <wcohen@xxxxxxxxxx> writes:
>
>> I have been looking at a PMDA that provides information about how long
>> it takes for packets to make their way from userspace to the network
>> device and from network device to userspace. [...]
>
> Neat.
>
>> network.interface.in.latency instance "devname"
>> network.interface.out.latency instance "devname"
>> [...]
>> (latency_sum[t]-latency_sum[t-delta])/(packets[t]-packets[t-delta])
>
> This sounds like just the sort of thing that we'd use dsmith's richer
> pcp-systemtap interface widgetry, currently being designed, and this
> computation could be one of its examples. Keep the ideas coming, and
> work with dsmith. (I would not suggest building just this into a
> separate PMDA.)
>
>
> - FChE
>
Hi Frank,
Is the a pointer to the pcp/systemtap integration that David Smith is working
on?
It is possible that similar latency measurements could be done for the block io
layer like the stuff that blktrace does. However, one concern is there could
be a huge number of items to track (in the tens of thousands) that might not
fit easily in a default sized associative array.
-Will
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