Comment 9 for bug 1759497

Each "mempool" in pulseaudio is 64 MB by default, and there's one mempool per client. Maybe gnome-shell has multiple connections to pulseaudio? 8 connections sounds excessive, though... Maybe the server's own mempool is visible in the client memory mapping too, so perhaps two mempools per connection are visible in the client memory map. 4 connections sounds still a bit much, though.

The mempools should indeed not have full "physical" impact unless they're actually fully used.

What if you set "shm-size-bytes = 33554432" (i.e. 32 MB) in /etc/pulse/client.conf and /etc/pulse/daemon.conf and reboot? Does the gnome-shell memory usage go down by 256 MB?