Re: Suggestion for laptop suspension

From: Richard Gooch (
Date: Wed Aug 30 2000 - 09:34:18 EST

Stephen Rothwell writes:
> Hi Richard,
> Richard Stallman <> writes:
> > On my laptop, suspending to disk is slow. It takes a whole minute, and
> > another minute to unsuspend--if all of core is in use. But it is much
> > faster when I do it not too long after the system was booted, when it has
> > not yet managed to use up most of core.
> >
> > This suggests that it could be nice to make the kernel empty its caches, and
> > mark all that core "unused", when a suspend is about to happen. I don't
> > know the details of how suspension works, so I am not sure this is possible,
> > but I think there are hooks for doing something in the kernel before a
> > suspend.
> Just to try something, could you please take the program below and change
> the 172 to be about 15-20 less that then number of MB of physical RAM
> you have, then compile and run it and then try to suspend to disk
> and see how long it takes. On my Thinkpad 600E, it changes the time
> to suspend from ~30 seconds to < 10 seconds.
> This is an experiment to see if your BIOS is faster to suspend
> when most of memory is zero'd.

Interesting. I've just tried this on my Dell Inspiron 3200 (144
MBytes) with a 110 MByte block of zeroes. The time went from 47
seconds (filled with 1s) to 20 seconds (filled with 0s).

Filling programme appended.


/* memfill.c

    Source file for memfill (fill memory with pattern and wait).

    Copyright (C) 2000 Richard Gooch

    This program 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 of the License, or
    (at your option) any later version.

    This program 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 this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

    Richard Gooch may be reached by email at
    The postal address is:
      Richard Gooch, c/o ATNF, P. O. Box 76, Epping, N.S.W., 2121, Australia.

/* This programme will fill memory with a specified pattern and wait.

    Written by Richard Gooch 30-AUG-2000

    Last updated by Richard Gooch 30-AUG-2000

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>

int main (int argc, char **argv)
    char length_modifier;
    signed long size_bytes, count, size_multiplier;
    unsigned char pattern;
    char *size_ptr;
    unsigned char *array;
    static char usage_string[] = "Usage:\tmemfill length[b|k|m] value";

    if (argc != 3)
        fprintf (stderr, "%s\n", usage_string);
        exit (1);
    size_ptr = argv[1];
    length_modifier = size_ptr[strlen (size_ptr) - 1];
    if ( isdigit (length_modifier) )
        size_bytes = strtol (size_ptr, NULL, 0);
        switch (length_modifier)
          case 'b':
          case 'B':
            size_multiplier = 1;
          case 'k':
          case 'K':
            size_multiplier = 1024;
          case 'm':
          case 'M':
            size_multiplier = 1024 * 1024;
            fprintf (stderr, "%s\n", usage_string);
            exit (1);
        size_ptr[strlen (size_ptr) - 1] = '\0';
        size_bytes = strtol (size_ptr, NULL, 0) * size_multiplier;
    pattern = strtol (argv[2], NULL, 0);
    if ( ( array = malloc (size_bytes) ) == NULL )
        fprintf (stderr, "Error allocating %ld bytes\n", size_bytes);
        exit (1);
    fprintf (stderr, "Filling...");
    for (count = 0; count < size_bytes; ++count) *array++ = pattern;
    fprintf (stderr, "\tfilled. Press control-C to stop\n");
    while (1) pause ();
    return (0);
} /* End Function main */
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