Re: [Xen-devel] [PATCH v9 1/6] x86: detect and initialize Cache QoS Monitoring feature

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 18.03.14 at 11:02, "Xu, Dongxiao" <dongxiao.xu@xxxxxxxxx> wrote:
> Previously due to the large amount of data, we use the method to let Xen 
> share the CQM pages to Dom0 in read only way to avoid data copy.
> However since the data amount is reduced a lot with above approach, do you 
> think whether we still need to use this share way? Or like most of the other 
> sysctl/domctl (e.g., xl list) command, which uses copy_to_guest() to pass the 
> data? 

Iirc we're talking about a square table with each dimension being the
socket count. Considering an 8-node 4-socket system, that would
still be 1024 entries, i.e. exceeding a page in size. Hence I would
think that the read-only sharing approach might still be better. Of
course, if the data amount was smaller (and by so much that even
on huge systems it's no more than a page), that would be different.

Jan


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