I recently noticed my local magento install was running quite slow in the admin. After banging my head against the wall looking at VM settings, I finally remembered that Magento has logs.

report.WARNING: Session size of 259759 exceeded allowed session max size of 256000. [] []

This was easily fixed by setting this value to unlimited and flushing the cache.

php bin/magento config:set system/security/max_session_size_admin 0
php bin/magento cache:flush