topic Re: avg_latency Measure in Software Development Kit (SDK) and API Discussions

avg_latency Measure

julioweber — Thu, 05 Jun 2025 07:07:48 GMT

Do anyone knows what this numbers means?

<instance-data>

<counter-data>

<name>parent_aggr</name>

<value>aggr0_Server1</value>

</counter-data>

<counter-data>

<name>avg_latency</name>

</counter-data>

<counter-data>

<name>total_ops</name>

</counter-data>

…

How can I read the avg_latency counter? Which measure and unit is used in it?

Re: avg_latency Measure

ryanc — Tue, 05 Oct 2010 15:44:39 GMT

For a general overview of how the performance counter system works, read through the description found in the SDK here:

<sdk dir>/doc/ontapi/ontapi_1.11/perf/index.html

Of specific interest is the explanation of how to interpret the various counter types:

raw: single counter value is used
delta: change in counter value between two samples is used
rate: delta divided by the time in seconds between samples is used
average: delta divided by the delta of a base counter is used
percent: 100*average is used

To understand more about a specific counter you can get details from the perf-object-counter-list-info API call:

<counter-info>

<name>avg_latency</name>

<desc>Average latency in microseconds for all operations on the volume</desc>

<privilege-level>basic</privilege-level>

<properties>average</properties>

<unit>microsec</unit>

<base-counter>total_ops</base-counter>

</counter-info>

Armed with this info, you should be able to interpret and present the latency values you are interested in. Make two calls to perf-object-get-instances, with a delay between them. Include both avg_latency and total_ops ( the base counter ).

From above we know 'average: delta divided by the delta of a base counter is used'. So perform the following calculation:

(avg_latency2-avg_latency1) / (total_ops2-total_ops1) => average latency in microseconds

To sanity test your application, compare your output with the output from ONTAP via the CLI:

Actual numbers: (598624907-596952932) / (149998706-149866390) => 12.636

filer1> stats show volume:vol0:avg_latency

volume:vol0:avg_latency:12.57us

Additionally, I'm not sure what language you are working with, but within the samples directory of the SDK there are a couple of perf related applications.

-ryan

Re: avg_latency Measure

Michael_Nye — Thu, 13 Feb 2014 12:04:34 GMT

Hi Ryan,

Your post has helped me immensely. A thousand thankyous.

-Mike

Re: avg_latency Measure

rle — Thu, 13 Feb 2014 17:50:28 GMT

You might want to check out this post for some Perl examples using the perf APIs.

Regards,

- Rick -

Re: avg_latency Measure

Michael_Nye — Fri, 14 Feb 2014 03:19:00 GMT

Once again - very helpful. Thankyou.