[fedora-virt] disabling ksm by default
Justin M. Forbes
jmforbes at linuxtx.org
Fri Oct 30 15:04:20 UTC 2009
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
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