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Re: Debugging memory leaks/stale references

From: Stefan Monnier
Subject: Re: Debugging memory leaks/stale references
Date: Mon, 27 Sep 2004 15:52:06 -0400
User-agent: Gnus/5.1006 (Gnus v5.10.6) Emacs/21.3.50 (gnu/linux)

> while they are traversed.  Unfortunately, no major leak turned up,
> just a few thousand cons cells which can't cause the massive leak I
> see (in the order of dozens of megabytes after entering/exiting a
> large NNTP group with Gnus).

I think it would be worthwhile to start with the basic info returned by
`garbage-collect' and such stuff.  See `memory-usage.el' below.
[ I thought you already tried that, but the few lines above make me think
that you don't even know whether the extra MBs are made up of cons cells, or
strings, or non-elisp-data, or ...]

> Is there a method to determine the (approximate) size of a buffer?

See buffer-size-bytes below.

> Are there any other objects that can change their size after
> allocation?  (I'm pretty sure that there are no additional Lisp
> objects allocated, but maybe an existing object grows without bounds.)

Yes.  Things like the specpdl "stack", the matrices used in display, maybe
the text-property-tree nodes, ...


;;; memory-usage.el --- Analyze the memory usage of Emacs in various ways

;; Copyright (C) 2002, 2004  Free Software Foundation, Inc.

;; Author: Stefan Monnier <address@hidden>
;; Keywords: maint

;; This file is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation; either version 2, or (at your option)
;; any later version.

;; This file is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs; see the file COPYING.  If not, write to
;; the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
;; Boston, MA 02111-1307, USA.

;;; Commentary:


;;; Code:

(defun buffer-size-bytes (b)
  "Return total number of bytes in the buffer contents."
  (with-current-buffer b
      (- (position-bytes (point-max)) (position-bytes (point-min))))))

(defun buffer-gap-bytes (b)
  "Return total number of bytes in the buffer gap."
  (with-current-buffer b

(defun buffer-total-bytes (b)
  "Return total number of ralloc bytes used by buffer."
  (with-current-buffer b
      (+ (position-bytes (point-max))
         (- (position-bytes (point-min)))

(defun memory-usage ()
  "List all buffers and their memory usage."
  (pop-to-buffer (get-buffer-create "*Buffer Details*"))
  (let* ((bufs (buffer-list))
         (num (length bufs))
         (gc-stats (garbage-collect))
         (conses (nth 0 gc-stats))
         (symbols (nth 1 gc-stats))
         (markers (nth 2 gc-stats))
         (strings (nth 3 gc-stats))
         (vectors (nth 4 gc-stats))
         (floats (nth 5 gc-stats))
         (intervals (nth 6 gc-stats)))
    (insert (format "Garbage collection stats:\n%s\n\n =>" gc-stats))
    (insert (format "\t%d bytes in cons cells\n" (* 8 (+ (car conses) (cdr 
    (insert (format "\t%d bytes in symbols\n" (* 24 (+ (car symbols) (cdr 
    (insert (format "\t%d bytes in markers\n" (* 20 (+ (car markers) (cdr 
    (insert (format "\t%d bytes of string chars\n" strings))
    (insert (format "\t%d bytes of vector slots\n" (* 4 vectors)))
    (insert (format "\t%d bytes in floats\n" (* 12 (+ (car floats) (cdr 
    (insert (format "\t%d bytes in intervals\n" (* 28 (+ (car intervals) (cdr 

    (insert (format "\nTotal bytes in lisp objects (not counting string and 
vector headers): %d\n\n"
                    (+ (* 8 (+ (car conses) (cdr conses)))
                       (* 24 (+ (car symbols) (cdr symbols)))
                       (* 20 (+ (car markers) (cdr markers)))
                       (* 12 (+ (car floats) (cdr floats)))
                       (* 28 (+ (car intervals) (cdr intervals))))))

    (insert (format "Buffer ralloc memory usage:\n%d buffers\n%d bytes total 
(%d in gaps)\n"
                    (apply #'+ (mapcar #'buffer-total-bytes bufs))
                    (apply #'+ (mapcar #'buffer-gap-bytes bufs))))
    (insert (format "%10s\t%s\t%s\n\n" "Size" "Gap" "Name"))
    (insert (mapconcat
             (lambda (b)
               (format "%10d\t%s\t%s"
                       (buffer-size-bytes b)
                       (buffer-gap-bytes b)
                       (buffer-name b)))
             (sort bufs (lambda (b1 b2)
                          (> (buffer-size-bytes b1) (buffer-size-bytes b2))))
    (insert "\n"))
  (goto-char (point-min)))

(provide 'memory-usage)
;; arch-tag: 04e012f0-3c59-4319-8d1a-e86204671ec5
;;; memory-usage.el ends here

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