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Re: [PATCH v8 08/13] xen/page_alloc: introduce preserved page flags macro
- To: Carlo Nonato <carlo.nonato@xxxxxxxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Mon, 6 May 2024 14:22:06 +0200
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- Cc: andrea.bastoni@xxxxxxxxxxxxxxx, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Mon, 06 May 2024 12:22:13 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 02.05.2024 18:55, Carlo Nonato wrote:
> --- a/xen/common/page_alloc.c
> +++ b/xen/common/page_alloc.c
> @@ -159,6 +159,7 @@
> #endif
>
> #define PGC_no_buddy_merge PGC_static
> +#define PGC_preserved (PGC_extra | PGC_static)
Seeing this again and its use ...
> @@ -1426,11 +1427,11 @@ static bool mark_page_free(struct page_info *pg,
> mfn_t mfn)
> {
> case PGC_state_inuse:
> BUG_ON(pg->count_info & PGC_broken);
> - pg->count_info = PGC_state_free;
> + pg->count_info = PGC_state_free | (pg->count_info & PGC_preserved);
> break;
>
> case PGC_state_offlining:
> - pg->count_info = (pg->count_info & PGC_broken) |
> + pg->count_info = (pg->count_info & (PGC_broken | PGC_preserved)) |
> PGC_state_offlined;
> pg_offlined = true;
> break;
... here: Shouldn't PGC_broken also be included in PGC_preserved?
> @@ -2484,6 +2485,11 @@ struct page_info *alloc_domheap_pages(
> }
> if ( assign_page(pg, order, d, memflags) )
> {
> + unsigned long i;
> +
> + for ( i = 0; i < (1UL << order); i++ )
> + pg[i].count_info &= ~PGC_extra;
For larger order this loop is non-trivial and may have a fair effect on
caches. Looking at the code just outside of upper patch context, is this
loop needed at all when MEMF_no_refcount is clear in memflags?
Jan
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