Re: [Embedded-pv-devel] [PATCH v10] xen: add para-virtual sound interface header file

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 24.11.16 at 18:25, <julien.grall@xxxxxxx> wrote:
> On 24/11/16 17:11, Oleksandr Andrushchenko wrote:
>> That is because we want to be cache line aligned.
> 
> But this is only accurate to your platform. There is HW available with 
> 128 bytes.
> 
> For instance on Xen ARM, all the structures are aligned to 128 bytes in 
> order to fit in most of cache line. Although technically it would be 
> possible have bigger one (see the definition of CSSIDR).

I think for "excessive" cache line sizes it is a good idea to balance
between the positive performance effect of having a single entry
per cache line and the amount of wasted space on the shared
ring. With that I think 64 is a reasonable compromise, which had
been agreed to also in earlier discussions on other interfaces (e.g.
the blkif indirect descriptor extension iirc).

Jan


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