Re: [RFC] Arch option to touch newly allocated pages

H. Peter Anvin
2002-03-07T18:22:29Z

Pavel Machek wrote:

> Hi!
>
>
>>>You say 'at once'. Does UML somehow give pages back to the host when they're
>>>freed, so the pages that are no longer used by UML can be discarded by the
>>>host instead of getting swapped?
>>>
>>Doesn't seem to but it looks like madvise might be enough to make that
>>happen. That BTW is an issue for more than UML - it has a bearing on
>>running lots of Linux instances on any supervisor/virtualising system
>>like S/390
>>
>
> I just imagined hardware which supports freeing memory -- just do not
> refresh it any more to conserve power ;-))).
>

> Granted, it would probably only make sense in big chunks, like 2MB or
> so... It might make sense for a PDA...
> Pavel

Unlikely. Also, if you're using ECC, then that really screws with you.

However, if it is an issue for more than UML (I still consider the
particular UML case "in case you have a UML on a tmpfs set up by an
idiot admin" completely bogus) then it's another issue. The S/390 issue
is real.

-hpa