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RE: [PATCH v4 10/14] migration: add support to migrate shared regions li
From: |
Wang, Wei W |
Subject: |
RE: [PATCH v4 10/14] migration: add support to migrate shared regions list |
Date: |
Fri, 10 Sep 2021 09:11:09 +0000 |
On Friday, September 10, 2021 4:48 PM, Ashish Kalra wrote:
> On Fri, Sep 10, 2021 at 07:54:10AM +0000, Wang, Wei W wrote:
> There has been a long discussion on this implementation on KVM mailing list.
> Tracking shared memory via a list of ranges instead of using bitmap is more
> optimal. Most of the guest memory will be private and the unencrypted/shared
> regions are basically ranges/intervals, so easy to implement and maintain
> using
> lists.
OK. At which version did you discuss this or do you have a link? (I didn't find
it in v9 KVM patches)
> A list will consume much less memory than a bitmap.
>
> The bitmap will consume more memory as it will need to be sized as per guest
> RAM size and will remain sparsely populated due to limited amount of
> shared/unencrypted guest memory regions.
I also thought about this. It depends on the guest.
I think "A list will consume much less memory" is true when we assume most of
guest pages are private pages.
>From design perspective, what if guest chooses to have most of its pages being
>shared?
Lists might consume much more memory than bitmaps in some cases, I think.
(Probably I can check your previous discussions first)
Best,
Wei