I think this dragon has not been put to sleep yet.  I ran into the
problem again - quite quickly within some 5 hours of emacs uptime

GNU Emacs 28.0.50 (build 1, x86_64-pc-linux-gnu, Motif Version 2.3.8,
cairo version 1.16.0) of 2021-03-08 (master commit a190bc9f3 - with
the motif removal reverted.)

  PID USER      PR  NI    VIRT    RES  %CPU  %MEM     TIME+ S COMMAND
21301 madhu     20   0 2988364   2.7g   0.0  36.7   5:04.01 S emacs

USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
madhu    21301  1.9 36.7 2988364 2809536 pts/2 Ssl+ 14:06   5:03 /12/build/emacs/build-motif/src/emacs -nw

A full gc does not release the resident memory.

I had an emacs -nw session and one X emacsclient session.  I was
prompted for a passwd by mew in the gui frame, and the prompt appeared
on the tty frame - which was where I entered the password. Then I
noticed the cpu temperature was up, and and a Ctrl-G on emacs stopped
that. I think the leak may have occured then but I didn't notice it
until later. When I did notice it i killed all the buffers did a gc
and ran the memory and malloc reports - which I'm attaching here - in
case it gives any clues.

The emacs command line was:

TERM=xterm-256color MALLOC_ARENA_MAX=2 exec /12/build/emacs/build-motif/src/emacs -nw" > ~/emacs.log 2>&1