On 25/04/2019 16:32, Tamas K Lengyel wrote:
> diff --git a/xen/include/asm-x86/mm.h b/xen/include/asm-x86/mm.h
> index 6faa563167..594de6148f 100644
> --- a/xen/include/asm-x86/mm.h
> +++ b/xen/include/asm-x86/mm.h
> @@ -133,7 +133,10 @@ struct page_info
> * of sharing share the version they expect to.
> * This list is allocated and freed when a page is shared/unshared.
> */
> - struct page_sharing_info *sharing;
> + struct {
> + struct page_sharing_info *info;
> + rwlock_t lock;
> + } sharing;
> };
>
> /* Reference count and various PGC_xxx flags and fields. */
I'm afraid this is a no-go, but for some reasons which are rather more
subtle that they appear here.
There is one struct page_info per 4k frame, and you've added an extra 16
bytes, taking it from 32 bytes to 48 bytes.
Other than making it a non-power-of-2 (net diffstat grow/shrink: 256/27
up/down: 7750/-5696 (2054) due to less efficient arithmetic[1]), the
framtable has a fixed virtual size (128G by default), so you've ended up
dropping Xen's memory limit (16TB by default) by 1/3.
~Andrew
[1] The drop is almost all in pdx_group_valid datastructure, which is a
function of the max supported memory limit.
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