[fedora-virt] disabling ksm by default

[Izik Eidus]

On 10/27/2009 05:46 PM, Justin M. Forbes wrote:
> On Tue, 2009-10-27 at 17:31 +0200, Izik Eidus wrote:
>    
>> On 10/27/2009 04:42 PM, Justin M. Forbes wrote:
>>
>>      
>>> While I do understand what you are saying, I don't think it is worth making
>>> a kernel change for at this point in the cycle.  Because ksm itself has a
>>> separate initscript, people who wish to use ksm will likely turn it on.
>>> This sets the max_kernel_pages to a reasonable value.  People who are not
>>> interested enough to turn on the ksm service are probably not the kind of
>>> people who will be checking to see how effective ksm is at all.
>>>
>>>        
>> To me it sound that users have no idea about this script, and ksm merge
>> to him just the zero pages of windows 7...
>>
>> My feeling is that 99% of the ppl in the world that will use it, would
>> just see the zero page merged and think "that is it..."
>> The current behaivor in fedora 12 is misleading the user (at least it
>> seems to me that it misslead that specific user)
>>
>> Btw we can set this value from userspace if we want "echo 0>
>> /sys/kernel/mm/ksm/run"
>>      
> Where would we put that in userspace? Another init script? I just
> updated to documentation on the feature page (and hopefully in the final
> release notes) to say that ksm can be enabled by running 'sudo chkconfig
> ksm on' in effort to draw more attention to these scripts.
>
> The other option is to make the ksm init script default to on, and just
> leave ksmtuned off at system start.  Since ksm is on by the default
> kernel, all we would be doing here is changing max_kernel_pages to a
> machine specific value.  The ksm init script is part of the qemu
> package, so it would only be changed on systems doing virt anyway.
>    

Sound Great to me, Can we please do that?

(I am sorry I came at such late time, but I saw that ppl just run ./qemu 
and think ksm is working effective when they see the memory shrink 
(while it truely just merge the zero pages for them - due to the 2000 
pages limit))

Thanks.

> Justin
>
>