[CentOS] cache memory not being used

Steve Bergman steve at rueb.com
Fri Oct 21 19:32:08 UTC 2005

Dave wrote:

>On 10/20/05, William Warren <hescominsoon at emmanuelcomputerconsulting.com> wrote:
>>18 megs of swap with a gig installed is nothing significant.  As far as
>>cached memory not being used.  If xorg is using 750 megs of ram there's
>>not a whole bunch left for a file cache after the other applications are
>>also allocated.
> The xorg memory consumtion is a different issue, I've had that
>problem for awile now, thats why I put in another 512 of ram so I can
>reboot twice a month instead of every weekend.
I'm getting into this thread late, but it's worth mentioning that top 
reports the total amount of *mapped* memory.  This includes video 
memory.  And on a card with 3D, the cards memory can be mapped 3 or more 
times, resulting in X looking like a huge memory hog. 

Also, current kernels are aggressive at freeing up application memory 
that is rarely used by swapping it out to make more room for caching 
disk data.  IMO, it's a win.  But if you do not like the behavior:

echo 0 > /proc/sys/vm/swappiness

(The range is 0-100. Default is 60.)

This will cause it to swap out only when it has to.  You can make the 
change permanent by setting vm.swappiness=0 in /etc/sysctl.conf

-Steve Bergman

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