Memory usage of writer process

The writer process seems to be using inordinate amounts of memory:

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+
COMMAND
11088 postgres  13  -2 3217m 2.9g 2.9g S    0 38.7   0:10.46 postgres:
writer process
20190 postgres  13  -2 3219m  71m  68m S    0  0.9   0:52.48 postgres:
cribq cribq [local] idle

I am writing moderately large (~3k) records to my database a few times
a second.  Even when I stop doing that, the process continues to take
up all of that memory.

Am I reading this right?  Why is it using so much memory?