Re: Is a swap partition still necessary in Linux?

From: Floyd L. Davidson (floyd_at_barrow.com)
Date: 08/22/04 

Date: Sun, 22 Aug 2004 07:58:32 -0800

Jeroen Geilman <not@rtpada.ln> wrote:
>Floyd L. Davidson wrote:
>> Jeroen Geilman <not@rtpada.ln> wrote:
>>
>>>>and it is good to have some swap available.
>>>
>>>Duh.
>>>Not only is it good, it is *required*.
>
>> It is not required.
>
>Let me qualify that:
>
>If you want to run without swap available (any kind) then
>running out of memory will invariably cause a kernel panic -
>dead.dead.dead.

Whether you have swap or not, you get an out of memory condition
when all _virtual_ _memory_ is exhausted; hence, if you have
256Mb of RAM and 256Mb of swap you can convert that to "virtual
memory" consisting of 512Mb of RAM only and have *exactly* the
same circumstances, except of course the later instance will 1)
be faster and 2) will not have any swap.

>This behaviour is unavoidable without kernel patches.

Typically the kernel starts killing off processes. It also
slows to a crawl. And to verify that, I just tried it on a
system that has only 64Mb of RAM, which makes it easy to cause
an out of memory condition by simply using xv to display half a
dozen images. Here's what the syslog entries were,

 Aug 22 07:45:53 cash kernel: Out of Memory: Killed process 2360 (bash).
 Aug 22 07:47:10 cash kernel: Out of Memory: Killed process 2215 (xterm).

No kernel panic. And given that it was my login shell and the
xterm it was displayed in, I didn't even need to reboot the
machine! 

-- 
FloydL. Davidson           <http://web.newsguy.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska)                         floyd@barrow.com

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