I've been using emacs-27.0.50 built from git for quite a some time, no
issues were found until recently.
Yesterday I've installed the latest version from source and got a few
issues with it.
1) Memory issues. In almost no time it ate >6Gb of RSS and around 8GB or
Virtual RAM. My OS: linux/arch, all default compilation options (no
change to conigure flags).
Just to compare it, I've worked with same code in same project but with
emacs-26.1.92 for another 6 hours and it only consumed 1.2Gb so far.
FWIW, I checked my Emacs instance – uptime 3 days, 21 hours – and I have 112.8MB private memory, 196.6 total (including OS toolkit memory returnable to the OS) on macOS. So, while I'm uncertain what our comparative load is, I'm definitely not seeing similar numbers on a build from last Thursday. This is on macOS, but past experience says that platform is more likely, not less, to show excessive memory use.