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Re: [PATCH 06/12] xen/common: add cache coloring allocator for domains
- To: Julien Grall <julien@xxxxxxx>, Carlo Nonato <carlo.nonato@xxxxxxxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Michal Orzel <michal.orzel@xxxxxxx>
- Date: Mon, 17 Oct 2022 11:16:27 +0200
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- Delivery-date: Mon, 17 Oct 2022 09:16:47 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
Hi Julien,
On 17/10/2022 10:44, Julien Grall wrote:
>
>
> Hi,
>
> On 17/10/2022 08:06, Michal Orzel wrote:
>> On 26/08/2022 14:51, Carlo Nonato wrote:
>> Apart from that, the memory coming from the buddy is of any color. Shouldn't
>> it be that the memory
>> allocated for domains comes from colored memory of the colors assigned to
>> them and anything else
>> should come from colors given to Xen? At the moment, the memory for e.g.
>> allocating P2M tables comes
>> from the buddy which means it can be of any color and might cause some cache
>> interference.
>
> Somewhat related. IIUC what you are saying, the P2M pool will still be
> allocated from the buddy. I would expect we want to instead allocate the
> P2M pool from the same color as the domain to prevent interference when
> the TLBs are loaded. Or is the interference negligible?
>
Good point and I agree. I do not think it is negligible.
All in all, allocating this memory from buddy which is of any color is
incorrect.
When cache coloring is enabled, it should not be possible to allocate memory of
any color.
If we can do this so that this memory comes from either Xen or domain colors,
the
intereference will be reduced. When it comes to P2M tables, if the memory comes
from
the colors assigned to a domain, there will be even less interference.
> Cheers,
>
> --
> Julien Grall
>
~Michal
|
