[RndTbl] Kernel 2.6 Swappiness

Jeff Green jmgreen7 at mts.net
Thu May 13 08:41:30 CDT 2004


Just a little heads up about something that kernel 2.6 users may not have 
noticed. When I installed the 2.6.5 kernel I was poking around '/proc' and 
noticed a file in '/proc/vm' called 'swappiness' (which had a value of 60). I 
had some idea about what it was for but there was no mention of it in the 
kernel docs. Later that day I was looking at http://kerneltrap.org and 
noticied this article: 

http://kerneltrap.org/node/view/3000?PHPSESSID=d5c5223a98199bf350e69d77c36ca785

It says 'swappiness' can be set between 0 and 100 (0 = no swapping, 100 = 
lotsa swapping) and mentions some recent discussions on the kernel mailing 
list about what 'swappiness' setting is ideal (i.e., don't swap anything to 
disk or swap everything to disk or some middle ground). The kernel 
maintainer, Andrew Morton, sets it 100 to free up as much memory as possible, 
while others think that desktop users don't want a delay when switching back 
to their apps so 'swappiness' should be closer to 0. I have it set at 25 now 
and it seems to work well (with 320 MB RAM) for everyday desktop use.

Just for completeness, if you want to set the 'swappiness' value use:

	sysctl -w vm.swappiness=x			[ 'x' being a value from 0-100 ]

And put:

	vm.swappiness=x

in '/etc/sysclt.conf' (or wherever 'sysctl.conf' is on you machine) to keep 
that value on reboot.

That's all for now.

Jeff Green




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