Redis Used Memory Negative?

I am using the redis input plugin of Telegraf.

As the Used_memory field of Telegraf is in bytes and it is incrementing, I have used a derivative function to get memory used in past 10 seconds. But sometimes, this gives me value of used_memory in negative. Why is this so ?
Any explanation is welcome. This below is the grafana dashboard.

@Luv Have you seen the non_negative_derivative function in the query language?

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Okay, thank you.

But any idea that why it is negative ?

@Luv I dont have the raw data, but I would imagine thats because the rate of change turns negative periodically. I’ve seen this before and always used non_negative_derivative to solve it.

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