Have seen this same behavior on multiple environments we have upgraded.
Before you upgrade to 4.1.x make sure you have at LEAST 16GB of RAM on your smartproxies PER CPU, because by default it will use one pulpcore-worker per cpu, and I am seeing them grow up to 16GB RAM each worker whenever doing a full sync to the smartproxy. It uses far less on optimized syncs but sometimes you have to do a full sync so you need it.
It appears that pulpcore is extremely ram hungry when syncing pulp3 rpm repos. (Ours is only RHEL8 repos right now). There is some related discussion on the pulp mailing list. Issue #8467: RQ worker takes up a lot of RAM when syncing OL7 repository - RPM Support - Pulp
Just thought I would warn people because this is a little different than pulp2 and what is mentioned in the install/upgrade guides at the moment.