Memory overhead of a large number of Partman partitions

[xcu]

I would like to understand how much can Partman contribute to memory usage in Postgres backend processes.

My application mainly runs SELECT statements in a partitioned table. The table is partitioned by size (100K rows per partition, 730 partitions in total). However, each Postgres backend process to run these SELECTs takes ~300 MB in memory, which seems a lot compared to what I've seen around.

work_mem is set to 16MB, so nothing too crazy. Also, I am using Pss to measure the memory used by each backend process so that shared_buffers don't mess the whole thing. Here's the output for a couple of them

Pss:             1260383 kB
Pss_Anon:         305501 kB
Pss_File:            199 kB
Pss_Shmem:        954682 kB

Pss:             1247796 kB
Pss_Anon:         293041 kB
Pss_File:            200 kB
Pss_Shmem:        954554 kB

Is this expected? Or the overhead of Partman partitions should be smaller in terms of memory consumption?