Re: [Xen-devel] Issue with PV superpage handling

[George Dunlap <George.Dunlap@xxxxxxxxxxxxx>]

On Mon, Jun 25, 2012 at 5:07 PM, Dave McCracken <dcm@xxxxxxxx> wrote:
>> Couldn't we have the setting be an override for the HVM
>> allocation behavior (defaulting to enabled there), and have
>> the originally intended meaning for PV (disabled by default)?
>
> I like this idea.  It would be simple enough.
>
> Is there any reason to allow disabling HVM superpage allocation?  HVM domain
> creation always allocates as many superpages as it can, then falls back to
> small pages for the rest.  Wouldn't it be reasonable to make restore always do
> this too?

At this point, probably not.  Every toolstack that I know of (xend,
xl, xapi) always set it to '1' for HVM guests.

Is there any reason not to just have the "superpage" flag mean "try to
use superpages", and then have the allocation routine fail if
superpages && pv==true?  It seems like that might be the simplest
option.

Alternately, we could change the argument to "pv_superpages" or
something, and ignore it for HVM guests (always trying to allocate
superpages if available).  But I'm not sure that really buys us
anything.  The only trick would be trying to help people in the future
to not make the same mistake I did in interpreting what the
"superpages" flag means.

 -George

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel