bug#38345: 27.0.50; Permanent increase in memory consumption after opening images (or pdfs)

[Eli Zaretskii <eliz@gnu.org>]

> From: Ihor Radchenko <yantar92@gmail.com>
> Date: Sat, 23 Nov 2019 22:37:44 +0800
> 
> Recently, I have noticed that my emacs tends to increase its memory
> usage up to over 1.5Gb after I open a large number of pdf documents. It
> is understandable since some of the pdfs can be quite large. However,
> the problem is that the memory does not seem to be released even after I
> close all the pdf buffers.
> 
> First, I though that the issue is with pdf-tools and reported my problem
> there (https://github.com/politza/pdf-tools/issues/177). However, the
> memory consumption problem appears to happen even if I just open images.
> 
> I monitored emacs (emacs -Q) memory usage with 
> https://github.com/dkogan/memory_leak_instrumentation
> 
> If I open a large (>250) photos using the code below, the memory usage
> increases permanently even after I close all the image buffers and wait
> for some time. 
> 
> #+begin_src emacs-lisp
> (setq large-file-warning-threshold nil)
> (setq image-cache-eviction-delay 5)
> (find-file "~/Tosort/pictures&photos/*.jpg" 'wild)
> (mapc #'kill-buffer (seq-filter (apply-partially #'string-match ".+.jpg$") (mapcar #'buffer-name (buffer-list))))
> (clear-image-cache t)
> (garbage-collect)
> #+end_src
> 
> The attached is memory consumption plot I got after running M-x
> eval-buffer on the code above several times (each run correspond to the
> memory consumption peak on the plot).

I see no attachment here, but isn't this because Emacs never returns
memory to the system when it frees it?