Re: [Xen-devel] [PATCH v2] x86/PoD: shorten certain operations on higher order ranges

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 28/09/15 15:30, Jan Beulich wrote:
> Now that p2m->get_entry() always returns a valid order, utilize this
> to accelerate some of the operations in PoD code. (There are two uses
> of p2m->get_entry() left which don't easily lend themselves to this
> optimization.)
>
> Also adjust a few types as needed and remove stale comments from
> p2m_pod_cache_add() (to avoid duplicating them yet another time).
>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> ---
> v2: Add a code comment in p2m_pod_decrease_reservation().
>
> --- a/xen/arch/x86/mm/p2m-pod.c
> +++ b/xen/arch/x86/mm/p2m-pod.c
> @@ -119,20 +119,23 @@ p2m_pod_cache_add(struct p2m_domain *p2m
>  
>      unlock_page_alloc(p2m);
>  
> -    /* Then add the first one to the appropriate populate-on-demand list */
> -    switch(order)
> +    /* Then add to the appropriate populate-on-demand list. */
> +    switch ( order )
>      {
> +    case PAGE_ORDER_1G:
> +        for ( i = 0; i < (1UL << PAGE_ORDER_1G); i += 1UL << PAGE_ORDER_2M )
> +            page_list_add_tail(page + i, &p2m->pod.super);
> +        break;
>      case PAGE_ORDER_2M:
> -        page_list_add_tail(page, &p2m->pod.super); /* lock: page_alloc */
> -        p2m->pod.count += 1 << order;
> +        page_list_add_tail(page, &p2m->pod.super);
>          break;
>      case PAGE_ORDER_4K:
> -        page_list_add_tail(page, &p2m->pod.single); /* lock: page_alloc */
> -        p2m->pod.count += 1;
> +        page_list_add_tail(page, &p2m->pod.single);
>          break;
>      default:
>          BUG();
>      }
> +    p2m->pod.count += 1 << order;

1UL

Otherwise, Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

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