At Fri, 10 May 2002 23:23:53 +1000 (EST), Jessica Mayo wrote:
> On Fri, 10 May 2002, peter anderson wrote:
> > I have been told that it can be beneficial to
> > configure two swapfiles. Is this right? What are the
> > benefits? Where would you use this?
>
> I have seen a number of assertions along these lines, but unless things
> have changed since I last looked over the swapfile logics, the second
> swapspace is never used until the second one is full. In this case, I can
> see no benifit at all.
>
> If this has changed with 2.4 kernels, I'd like to know... :)
(note the "->" marked sentence)
swapon(8):
-p priority
Specify priority for swapon. This option is only
available if swapon was compiled under and is used
under a 1.3.2 or later kernel. priority is a value
between 0 and 32767. See swapon(2) for a full
description of swap priorities. Add pri=value to
the option field of /etc/fstab for use with swapon
-a.
swapon(2):
PRIORITY
Each swap area has a priority, either high or low. The
default priority is low. Within the low-priority areas,
newer areas are even lower priority than older areas.
All priorities set with swapflags are high-priority,
higher than default. They may have any non-negative value
chosen by the caller. Higher numbers mean higher prior�
ity.
Swap pages are allocated from areas in priority order,
highest priority first. For areas with different priori�
ties, a higher-priority area is exhausted before using a
-> lower-priority area. If two or more areas have the same
-> priority, and it is the highest priority available, pages
-> are allocated on a round-robin basis between them.
As of Linux 1.3.6, the kernel usually follows these rules,
but there are exceptions.
--
- Gus
--
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