Re: Question about partitioning shared cache in Xen

["Jan Beulich" <JBeulich@suse.com>]

>>> On 14.01.15 at 15:45, <xumengpanda@gmail.com> wrote:
> Yes. I try to use the bits [A16, A12] to isolate different colors in a
> shared cache. A 2MB 16-way associate shared cache uses [A16, A6] to
> index the cache set. Because page size is 4KB, we have page frame
> number's bits [A16, A12] overlapped with the bits used to index a
> shared cache's cache set. So we can control those [A16, A12] bits to
> control where the page should be placed. (The wiki pages about page
> coloring is here: http://en.wikipedia.org/wiki/Cache_coloring)

But the majority of allocations done for guests would be as 2M or
1G pages, so picking address bits 12..16 for coloring seems rather
undesirable. (And surely no LLC would be large enough any time
soon to allow coloring of 1G pages anyway.)

Jan