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

[Jarod Wilson <jwilson@xxxxxxxxxx>]

Alex Williamson wrote:
> 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.

I pretty much *always* do, prior to this patch. :)

>> 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...

I'll add that once we iron out a few more things...

>> +       /* 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,

Yeah, I borrowed that straight from Akio's patch. Sounds like we could
use some work here to make it more accurate.

-- 
Jarod Wilson
jwilson@xxxxxxxxxx

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