[Xen-devel] RE: tmem - really default to on?

[Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>]

> >>> Dan Magenheimer <dan.magenheimer@xxxxxxxxxx> 04.02.10 22:01 >>>
> >A) There is some order>0 memory allocation in Xen domain creation
> >that doesn't fall back to order=0, that I've not seen in my testing
> >but shows up in your systems (or has very recently been added).
> >If true, this is a problem not only for tmem but also for all other
> >memory optimization work and we need to identify and (if possible)
> >fix it.
> 
> This is the case - x86's shadow code does all its allocations as order-
> 2
> with no (possible the way things are designed) fallback.

Hmmm.... so this would affect HVM creation but not PVM, but also
could cause PVM live migration to fail, correct?

> Also, the domain structure itself is of order 4 (38k), obviously
> without
> fallback (and even with address range restriction, though that one
> is affecting only really big machines, and it could be lifted to
> effectively not be a restriction anymore, i.e. just serve documentation
> purposes).

This has likely been avoided by luck when lots of memory is
flushed from tmem and returned to the Xen heap and consolidated.

Are you suggesting that the domain structure could/should have
two sizes, dynamically chosen by machine size?  Or something
else?

In any case, I'd still suggest turning tmem off in your dom0
is the best short-term solution.

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