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Re: [fedora-virt] disabling ksm by default



On 10/27/2009 12:12 PM, Mark McLoughlin wrote:
Hi Izik,

On Tue, 2009-10-27 at 00:55 +0200, Izik Eidus wrote:
Hi, I saw that Fedora 12 will have ksm tunning script that control the
ksm speed / kernel pages allocation.

The only problem that I have is - as far as I remember ksm is by default
enabled and only with 2000 kernel pages...
What I am worried about is that users wont use the ksm tunning script
and would just run ksm with this 2000 kernel pages -
the result would be that ksm will probably merge just the zero pages
(that could be alot of memory) and the user might not know
that much more memory can be saved...

Is it possible to at least make ksm disabled by default? so the users
will have to run the ksm tunning script when they want to start ksm?
ksm is disabled by default currently

Ok so we are fine then.

And if we set it to disabled by default, cant we set the initialized
values into more realistic value? (like 1/4 of the memory in the
mainline kernels? )
Here's the logic we have in the init script:

   # unless KSM_MAX_KERNEL_PAGES is set, let ksm munch up to half of total memory.
   default_max_kernel_pages () {
       local total pagesize
       total=`awk '/^MemTotal:/ {print $2}' /proc/meminfo`
       pagesize=`getconf PAGESIZE`
       echo $[total * 1024 / pagesize / 2]
   }

git tree for the scripts here:

   http://gitorious.org/ksm-control-scripts/ksm-control-scripts

Suggestions, comments, patches etc. welcome


Thanks.


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