EBS init hell

I should remind myself that there is some initial penalty for creating an EBS volume on AWS - right after creation it is really slow to access for a good while.

It's a gp2 volume and iotop reports a 5 MB/s access speed, in agreement with the CloudWatch metrics.

I am wondering for how long - the stuff on this link suggests straight after first access it starts feeling fine.

However, I can see it being slow on the second run of the recommended

dd if=/dev/xvda of=/dev/null bs=1M

okay I only partially ran it at first, but I'd expect walking the blocks to be a very deterministic process for dd. So maybe it's rather the first complete access? Or a few hours of initialization, such as the case is a large enough chunks when growing a volume or e.g. with a complete drive type change (i.e. gp2-io1)?

Well, I give up on that for today/night but best remember this caveat ...

Update: really a little googling confirms this... that it needs a complete read through:
https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ebs-initialize.html