Max swap size use-to-be 2GB on ia32, HAS THIS CHANGED? & on x86_64?

Antryg · 12-28-2007, 05:01 AM

I've found damn-little actual documentation/information about this,
so if someone could point me to something ( like kernel-code that has comments, ferinstance )
that gives correct information, I'd appreciate it.

I've found nothing even remotely recent in tldp.org
( gave up after a WfW-3.1/Linux item ), http://www.linuxquestions.org/questi...ze#post2869823
indicates 2GB is a hard-limit,

RedHat 7.1 had a 2GB hard-limit,
openSUSE ( my distro ) wiki says nothing that I can find on it,
& there's nothing in /usr/src/linux/Documentation/ for some damned reason. . .

Also is it different for ia32 & for x86_64?

==========

Free tip for coders & webmeisterses:
in ~/.bashrc
xmodmap -e "keycode 65 = space underscore nobreakspace endash"
xmodmap -e "keycode 115 = Mode_switch" # Left "Windows"-Key
# What that does is make 4 symbols/key available:
# Normal-spacebar == space
# Shift+space == underscore ( no more reaching up-right for it )
# Mode_switch(left-Win-key)+space == nobreakspace
# Mode_switch+shift+space == endash ( for typesetting:
#use "space endash space", instead of just sticking a
#double-hyphen between phrases: it's MUCH more readably clear! )

# The only key /given/ 4 symbols here, is space-bar ( keycode 65 ).

# see /usr/include/X11/keysymdef.h for the possibilities!!

# use "xev" command-line util to discover the keycodes for
# your multimedia-keyboard & make them thar extra keys useful!

xset r rate 210 35
# saner delay/repeat-rate

These set the keyboard up More Gooder(tm), see. . .

: )

Lenard · 12-28-2007, 06:43 AM

Hmmmm..........

See: http://www.novell.com/linux/techspecs.html
Click on the Kernel Limits if need be.

LinuxManMikeC · 12-28-2007, 07:22 AM

Quote:

Originally Posted by Antryg

http://www.linuxquestions.org/questi...ze#post2869823
indicates 2GB is a hard-limit,

The hard limit they were talking about in that thread only refers to the maximum size of a single swap file system. Therefore, you could have 2 2GB swap partitions making 4GB of swap, and so on up to a certain limit (whatever it may be).

Now that SUSE documentation is interesting. A max total of 2TB. From what I can gather from the "32 * 64 GB" notation, I interpret it as a max of 32 swap file systems and a max of 64GB per swap file system. If this is the configuration on all distros, who knows. However, I will soon have 160GB of free space on which to test these limitations. I will report back when I do it (if I remember

).

Lenard · 12-28-2007, 09:03 AM

To LinuxManMikeC;

You should note that this information from SuSE also applies to other versions of Linux as well. The swap space is not limited to 2-GB per swap partition / swap file with the current 2.6 kernel series as the SuSE documentation notes it is now 64-GB per swap partitions and/or swap files.

LinuxManMikeC · 12-28-2007, 09:50 AM

Cool, I figured it was well over 2GB by now. Now, what could I possibly do with 2TB of swap? I barely scratch the surface of my 2GB as it is.

Lenard · 12-28-2007, 11:12 AM

I know which is why mine is only about 1-GB on my 2-GB RAM laptop(minus the shared video memory);

Code:

$ free
             total       used       free     shared    buffers     cached
Mem:       1801520    1163544     637976          0     172184     607104
-/+ buffers/cache:     384256    1417264
Swap:      1116476         64    1116412

Antryg · 01-08-2008, 11:28 PM

Thanks All who replied with helpfulness.

64GB is a nice single swap limit, eh?

As for needing it, the machine I'm setting-up has 4GB ECC RAM & 2GB swap, but some programs leak ( all Mozilla apps, e.g. ), and when Thunderbird is eating upwards of 800MB after awhile, and every other app tries-to, yes I sometimes get into trouble for not having enough swap ( crashed for running out, just the other day ).

Some app mem-usage Right Now:
Firefox = 470MB
Thunderbird = 400MB
NVU = 380MB
StoryLines = 300
Zen Updater = 270MB
Konq = 260MB

of course, this particular session, I haven't been into heavy/complex stuff, so these are all small, compared with what sometimes happens. . .

And I remember when "emacs" stood for Eight Megs, And Continuous Swapping!

syg00 · 01-09-2008, 01:11 AM

That's a theoretical limit - I would be surprised if 2 Gig isn't still the actual (usable) size of each extent for most users.
Redhat did a patch to mkswap for RHEL, but a quick look at the code from kernel.org doesn't show the Redhat modifications have made it upstream.
Don't know about Suse.