Re: a swap partition utilization question

["Michael French" <mfrench@ashevillemail.com>]

    From a website I found:

http://www.netadmintools.com/art1.html
 by Urbana Der Ga'had

Sometimes in the course of a system's existence you find that the swap
partition you set up at install-time just isn't enough anymore. Maybe you're
upgrading your system to RedHat 7.1 from a version of RedHat that used less
swap in relation to physical RAM. Perhaps you're running Oracle. Or maybe
you're adding more memory and would like to increase swap space accordingly.


Our machine goblin is swapping like mad and we just can't take it down right
now to add more RAM. So to keep the machine from running out of memory
entirely and freezing, we'll add 128 MB more swap space by creating a swap
file.


First we check out the memory usage:


[root@goblin /root]# free -m
             total       used       free     shared    buffers     cached
Mem:           251        242          8         22         11         32
-/+ buffers/cache:        198         52
Swap:          133        133          0

Make sure we have 128 MB laying around somewhere:


[root@goblin /root]# df
Filesystem           1k-blocks      Used Available Use% Mounted on
/dev/hda9               132207     33429     91952  27% /
/dev/hda1                15522      2537     12184  17% /boot
/dev/hda6              6143236    739000   5092176  13% /opt
/dev/hda7              1035660    836204    146848  85% /usr
/dev/hda5              2071384    344048   1622112  17% /usr/local
/dev/hda8               303344     14439    273244   5% /var
OK, we're going to make a swap file in /opt by using dd to create a file 128
MB in size.

[root@goblin /opt]# dd if=/dev/zero of=swapfile bs=1024 count=132207
132207+0 records in
132207+0 records out
[root@goblin /opt]# ls -l
total 132364
drwxr-xr-x   20 brenda users        4096 May 22 10:46 brenda
drwxr-xr-x    2 root     root        16384 Feb 21 07:04 lost+found
-rw-r--r--    1 root     root     135379968 May 29 11:52 swapfile
Hey, I know, let's not make it world-readable...

[root@goblin /opt]# chmod 600 swapfile
[root@goblin /opt]# ls -l
total 132364
drwxr-xr-x   20 brenda users        4096 May 22 10:46 brenda
drwxr-xr-x    2 root     root        16384 Feb 21 07:04 lost+found
-rw-------    1 root     root     135379968 May 29 11:52 swapfile
Now we set up the swap area and enable it.

[root@goblin /opt]# mkswap swapfile
Setting up swapspace version 1, size = 135372800 bytes
[root@goblin /opt]# swapon swapfile
And viola! Twice as much swap as before.

[root@goblin /opt]# free
total       used       free     shared    buffers     cached
Mem:        257632     254632       3000       2512      36172      15096
-/+ buffers/cache:     203364      54268
Swap:       268708     136512     132196
You can edit /etc/fstab to enable your swap file automatically at boot time.
By adding an entry like this:

/opt/swapfile swap swap defaults 0 0

Sure, swapping's ugly, slow and will grind your hard drives to dust. But
even modern systems which have been tuned for performance require a generous
oodle of swap space.


Michael French

----- Original Message ----- 
From: "Darío Mariani" <dmarian@fi.uba.ar>
To: <linux-admin@vger.kernel.org>
Sent: Tuesday, November 25, 2003 1:41 PM
Subject: Re: a swap partition utilization question


> Try creating a program that consumes 90% or more of the physical memory.
>
> chuck gelm net wrote:
> > Hi, Bill:
> >
> >  Perhaps swap memory will not be used until
> > all physical memory has been consumed.
> >
> > HTH, Chuck
> >
> > "Bill J.Xu" wrote:
> >
> >>Hello everyone,
> >>
> >>After booting my linux box,I add a swap partition using "swapon
/dev/hda5".but I found that swap partition was nerver used even 2M physics
memory left.
> >>
> >>why?
> >>
> >>thanks
> >>
> >>Bill
> >>-
> >>To unsubscribe from this list: send the line "unsubscribe linux-admin"
in
> >>the body of a message to majordomo@vger.kernel.org
> >>More majordomo info at  http://vger.kernel.org/majordomo-info.html
> >
> >
> > -
> > To unsubscribe from this list: send the line "unsubscribe linux-admin"
in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> >
>
>
> -
> To unsubscribe from this list: send the line "unsubscribe linux-admin" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>

-
To unsubscribe from this list: send the line "unsubscribe linux-admin" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html