Jerry Geis wrote:

Hi all,

I used to use centos 4.5 on an AMD 4800+ with 2GIG ram. Now I use centos 5.1 on AMD 6400+ with 4GIG RAM.

The system responsiveness is different between the two. I noticed that centos 5.1 seems to be swapping programs out of memory at times resulting in slowness (perceived by me).

I played with swappiness (/proc/sys/vm/) setting to 10, then 1 then 0. Still resulted in the same perceived slowness. Today I did swapoff -a and now the system obviously does not swap anything out all all. I thought thats what swappiness of 0 would have done.

Are others experiencing this also? The perceived slowness maks the older system with less RAM and slower CPU "seem" faster.

Any suggestions on other things to try?

When you reset swappiness, how did you do it.

The way that I have had the most luck in is editing /etc/sysctl.conf and adding:

vm.swappiness=10

(or in your case, 0)

and then:

sysctl -p /etc/sysctrl.conf

You would need to then make the things already swapped out come back (will happen over time) .. but rebooting is easier and faster.

That should work ... but will not prevent all swapping.

On 01/02/2008 01:53, Jerry Geis wrote:

Hi all,

I used to use centos 4.5 on an AMD 4800+ with 2GIG ram. Now I use centos 5.1 on AMD 6400+ with 4GIG RAM.

The system responsiveness is different between the two. I noticed that centos 5.1 seems to be swapping programs out of memory at times resulting in slowness (perceived by me).

I played with swappiness (/proc/sys/vm/) setting to 10, then 1 then 0. Still resulted in the same perceived slowness. Today I did swapoff -a and now the system obviously does not swap anything out all all. I thought thats what swappiness of 0 would have done.

Are others experiencing this also? The perceived slowness maks the older system with less RAM and slower CPU "seem" faster.

Any suggestions on other things to try?

Jerry

Large amounts of swap "in use" does not necessarily reflect a system that is swapping heavily, and your perceived slowness may have another cause.

Take a look at the output of "vmstat 10" command's swap columns for real time or "sar -W" for historical information regarding the number of pages being swapped in and out. These numbers will give you a much more accurate picture of how much swapping is occuring on your system.

Cheers Luke