[NTLUG:Discuss] controlling swapping

David Camm bbai at onramp.net
Tue Nov 16 21:41:02 CST 1999


since installing our new server (redhat 5.2, 500M RAM), i've noticed
that the system is swapping even though it is idle (via procinfo) over
99% of the time. [what a tribute to the efficiency of linux!]

looking thru the docs, i discovered a small article in
/usr/src/linux-2.0.36/Documentation called memory-tuning.txt which
describes the contents of /proc/sys/vm/freepages.

the freepages 'file' on the new server contains:  1046    1569    2092 
which implies that the machine will start background swap when there are
less than 2092*4096 bytes free memory and will start foreground swap
when less then 1569*4096 free memory.

the old machine, with 256M RAM has the following values: 532     798    
1064 , which seem much more reasonable, given that the machines
effectively have the same workload (serving web sites).

questions are - can i safely lower the values in the new machine, and
can these be set via 
echo 'xxx yyy zzz' >/proc/sys/vm/freepages while the machine is running,
as can be done with other proc files such as /proc/sys/kernel/file-max

the docs mentioned that the other files in proc/sys/vm are 'arcane' and
that the meaning of the contents is not widely known.  just out of
curiosity, does anyone (other than linus) have an idea as to what they
are and what effect they may have?

thanks in advance,

david camm
@dvnaced web systems




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