RE: why swap is important?
If Debian runs out of memory space, it will arbitrarily start killing
processes to clear up memory. This has unpredictable and possibly
catastrophic consequences.
If Debian runs out of physical memory and swap space is available, it can
save sections of physical memory to disk that are not currently in use,
opening up new physical memory sections (a.k.a pages) for use by
applications.
Swapping memory pages in and out is an expensive process, mainly due to
slowness of disk access compared to ram access. Thus, it is not ideal and
you will see a noticable performance hit if a machine starts to spend a
significant amount of time swapping. Kernel developers have spent a lot of
time trying to optimize what memory gets swapped out in order to delay any
sort of performance impact.
Even if you feel you have enough physical memory, software bugs or other
unpredicted circumstances (running Windows for instance) can cause runaway
memory use. I personally would like to notice a performance hint and be
able to investigate on a working system, rather than have arbitrary
processes killed.
Joe
-----Original Message-----
From: j smith [mailto:rootof3@yahoo.com]
Sent: Friday, February 25, 2005 4:27 PM
To: debian-user@lists.debian.org
Subject: why swap is important?
i have enough RAM, but Debian 3.0 installation screen
says i'd better make a swap, why?
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