what is causing random spikes in local mysql server query speeds?

Question

So while playing around on my localhost in phpMyAdmin and doing some stuff with SQL, I realized that I would randomly get huge spikes in the time it took to perform a database query. I have a database table with about 3000 entries, and I was running a very simple query to display the first 2500 of them.

On average, running this query was taking around 0.003 to 0.004 seconds. (Of course, loading the phpMyAdmin page took much longer, but we're just looking at the query times.) However, I noticed that occasionally the query times would go up past 0.01. Once it even shot up to 0.04. So, my curiosity getting the better of me, I decided to repeatedly run the same query, and produced a graph of my results:

I'm not running anything else on my computer that may be interacting with MySQL, and because it's my localhost I'm the only one that's doing anything to mess with my database (right?). Slight outliers are understandable, but what's causing the load times to go up anywhere from 3 to 30 times, completely randomly it seems?

Can anyone help me satiate my curiosity?

Answer 1

I'm not running anything else on my computer that may be interacting with MySQL

But is there anything else running on your computer that might be interacting with your hard drive /CPU on a regular basis? Because that would explain the spikes. Maybe have a scan of running processes, and compare the cpu/disk activity against the spikes.

Answer 2

Even though your database is running on your local host, it's not running in complete isolation. It is competing for your system's resources with every other process you have running.