12-29-2003
Preßy, there is some truth to what you're saying. But 2x memory is still a good calculation. Let's take one step at a time.
Before risc, 32 K was a common memory size and 512 K was a lot of memory. In those days, unix would not allocate a page of memory unless it could also allocate swap for it. If you had 32 K memory, you needed 32 K of swap just to use it all. If wanted to be able to use more than 32K of memory on your 32K machine, you needed 2 or 3 times the swap space. This was not seen as a problem. Disks were very big compared to memory.
Risc changed things. Suddenly we had 32 MB of memory and 300 MB disks. Two to three times memory was a big deal. Someone noticed that a kernel would never swap everything out leaving memory empty. So various schemes were implemented to change that way things work. You can now have 1 GB of memory and .5 GB of swap and things will work. There is a price for this which varies from OS to OS. And you may need to tune the kernel to get it to work.
But disks have caught back up with memory. The old ratios have been matched and even surpassed. 1 GB of memory is a lot. But 2GB of swap is small change. Even my laptop has an 80 GB disk.
Running out of swap is still a disaster. So yes, with modern equipment 2 or 3 times memory is good again. If you have a early 90's system, this won't be true for you. But it's time to upgrade those 500 MB washing-machine-sized drives anyway.
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LEARN ABOUT SUSE
glib::flags
Glib::Flags(3) User Contributed Perl Documentation Glib::Flags(3)
NAME
Glib::Flags
DESCRIPTION
Glib maps flag and enum values to the nicknames strings provided by the underlying C libraries. Representing flags this way in Perl is an
interesting problem, which Glib solves by using some cool overloaded operators.
The functions described here actually do the work of those overloaded operators. See the description of the flags operators in the "This
Is Now That" section of Glib for more info.
HIERARCHY
Glib::Flags
METHODS
scalar = $class->new ($a)
o $a (scalar)
Create a new flags object with given bits. This is for use from a subclass, it's not possible to create a "Glib::Flags" object as such.
For example,
my $f1 = Glib::ParamFlags->new ('readable');
my $f2 = Glib::ParamFlags->new (['readable','writable']);
An object like this can then be used with the overloaded operators.
scalar = $a->all ($b, $swap)
o $b (scalar)
o $swap (scalar)
ref = $a->as_arrayref
integer = $a->bool ($b, $swap)
o $b (scalar)
o $swap (integer)
integer = $a->eq ($b, $swap)
o $b (scalar)
o $swap (integer)
integer = $a->ge ($b, $swap)
o $b (scalar)
o $swap (integer)
scalar = $a->intersect ($b, $swap)
o $b (scalar)
o $swap (scalar)
integer = $a->ne ($b, $swap)
o $b (scalar)
o $swap (integer)
scalar = $a->sub ($b, $swap)
o $b (scalar)
o $swap (scalar)
scalar = $a->union ($b, $swap)
o $b (scalar)
o $swap (scalar)
scalar = $a->xor ($b, $swap)
o $b (scalar)
o $swap (scalar)
SEE ALSO
Glib
COPYRIGHT
Copyright (C) 2003-2009 by the gtk2-perl team.
This software is licensed under the LGPL. See Glib for a full notice.
perl v5.12.1 2010-07-05 Glib::Flags(3)