Sudden grow of memory in "Laundry" state

[Robert]

Hi, I have a server with FreeBSD 11.2 and 48 Gigs of RAM where an app 
with extensive usage of shared memory (24GB allocation) is running.

After some random amount of time (usually few days of running), there 
happens a sudden increase of "Laundry" memory grow (from zero to 24G in 
a few minutes).

Then slowly it reduces.

Are described symptoms normal and expected? I've never noticed anything 
like that on 11.1.

Thanks.