Re: [Xen-ia64-devel] [PATCH] Use saner dom0 memory and vcpu defaults, don't panic on over-allocation

[Alex Williamson <alex.williamson@xxxxxx>]

Hi Jarod,

On Tue, 2007-07-31 at 23:03 -0400, Jarod Wilson wrote:
> So as a safer and less-crippling compromise, based on some of the code
> originally proposed in that thread, I'm proposing that dom0 try to
> come
> up on up to 4GB of RAM and 4 cpus by default. The attached patch
> implements that proposal. Exact values can be tweaked a bit, if deemed
> necessary, don't get hung up on that too much.

   This seems like a reasonable default to me.  I usually end up
specifying increased dom0 memory and cpu in my elilo.conf anyway.

> One nice additional bit this patch adds is support for handling the
> case
> where the user requests slightly more memory than is physically
> available without a kernel panic.

   Yes, this would be a good feature.

> Comments/criticism/acceptance welcomed...

   We'll need a Signed-off-by, and...

> +       /* maximum available memory for dom0 */
> +       max_dom0_pages = avail_domheap_pages() -
> +                        min(avail_domheap_pages() /
> +                        16UL, 512UL << (20 - PAGE_SHIFT)) ;

   I assume this heuristic came from Akio's patch in the thread you
referenced; can anyone explain how this was derived and why it's
necessary?  It looks like a fairly random fudge factor.  Thanks,

        Alex

-- 
Alex Williamson                             HP Open Source & Linux Org.


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