Re: [fedora-virt] disabling ksm by default

["Justin M. Forbes" <jmforbes linuxtx org>]

On Fri, Oct 30, 2009 at 10:00:28AM +0000, Richard W.M. Jones wrote:
> On Tue, Oct 27, 2009 at 10:12:49AM +0000, Mark McLoughlin wrote:
> > ksm is disabled by default currently
> [...]
> >   # unless KSM_MAX_KERNEL_PAGES is set, let ksm munch up to half of total memory.
> 
> Mark, can you summarise why we wouldn't want KSM to be enabled by
> default, and why we need to limit it to half of total memory?
> 
The limit to half of total memory is because ksm pages are unswappable at
this time.  To be fixed in a future kernel.  As for  enabling by default,
the more I think about it, the more this makes sense.  The ksm initscript
is shipped with qemu, so anyone with it installed should be interested in
virt, and the value of max_kernel_pages doesn't matter if you are not
running anything which marks memory mergeable, which only kvm does at the
moment.

Justin