connect a device -> RAM usage skyrocketed

[rustamusmanov973]

I tried to connect some devices while using exwm (with clean dotspacemacs/user-config () and some packages, including exwm installed):

1. Airpods pro (connecting via bluetooth -> PulseAudio Volume control program -> switch output source)
2. keyboard natural ergonomic 4000: unplug the usb (when using exwm) and then if you try to plug it back, RAM usage skyrockets

htop displays processes "emacs" eating more and more RAM (quickly). RAM usage increases: smth like 2-3GB (yes, GB)/second.
everything freezes. Ctrl+G doesn't seem to solve the problem. Sometimes RAM usage increases to some level and stops increasing, but remains astronomically high (like +6 GB).
Sometimes tty3 (ctrl+alt+f3) works and I can kill emacs (killall emacs).
I failed to find out what is happening using "Emacs Memory Debugging" article in the wiki.

OS: 5.15.81-1-MANJARO linux

[vedvyas]

I've also had this problem for years, especially when (dis)connecting USB devices. Haven't investigated it much but have had success with the solution from http://notes.secretsauce.net/notes/2016/04/08_glibc-malloc-inefficiency.html of calling malloc_trim from the Emacs process. Reproducing their script here with minor changes to the trim call:

#!/bin/sh
# malloc-trim.sh
# From http://notes.secretsauce.net/notes/2016/04/08_glibc-malloc-inefficiency.html

set -e

PID=$1
test -n "$PID" || { echo "Need PID on the cmdline" > /dev/stderr; exit 1; }

before=`ps -h -p $PID -O rss  | awk '{print $2}'`
gdb --batch-silent --eval-command 'call (int)malloc_trim(0)' -p $PID
after=`ps -h -p $PID -O rss  | awk '{print $2}'`

echo "before: $before"
echo "after: $after"
echo "freed: $(($before - $after))"

Note that this is glibc-specific. It has been pretty robust when run from inside an EXWM session or another TTY when the session is unresponsive. There was a window of Emacs/userspace-stuff/kernel versions in the past when it would sometimes hose my Emacs process.

Considering that it seems to work and that Emacs' memory usage continually grows in this scenario: could it be that the device (dis)connects lead to a rapid instantiation of many short-lived objects in XELB/EXWM?