Messages in this thread | | | Date | Wed, 02 Apr 2008 15:13:05 -0700 | From | Jeremy Fitzhardinge <> | Subject | Re: [PATCH RFC] hotplug-memory: refactor online_pages to separate zone growth from page onlining |
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Dave Hansen wrote: > On Wed, 2008-04-02 at 14:35 -0700, Jeremy Fitzhardinge wrote: > >> Dave Hansen wrote: >> >>> Oh, once we've let Linux establish ptes to it, we've required that the >>> hypervisor have it around? How does that work with the balloon driver? >>> Do we destroy the ptes when giving balloon memory back to the >>> hypervisor? >>> >> Yep. It removes any mapping before handing it back to the hypervisor. >> > > Wow. So does Xen ever use PSE to map kernel data? That sucks. >
Not at present. But I'd like to change it to manage memory in largepage chunks so that we can.
> Yeah, but I'm just talking about hotplugged memory. When we add it, we > don't have to map the added pages (since they're highmem) and don't have > to touch their contents and zero them out, either. Then, the balloon > driver can notice that the memory is too large, and start to balloon it > down. >
I didn't think x86-64 had a notion of highmem.
How do you prevent the pages from being used before they're ballooned out?
>> Everything also applies to x86-64. >> > > Not really, though. We don't have the page->flags shortage or lack of > vmemmap on x86_64.
Right now, I'd rather have a single mechanism that works for both.
J
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