On 05/09/2018 23:58, Wei Yang wrote:
> On a 64bits machine, struct is naturally aligned with 8 bytes. Since
> kvm_mmu_page member *unsync* and *role* are less then 4 bytes, we can
> rearrange the sequence to compace the struct.
>
> As the comment shows, *role* and *gfn* are used to key the shadow page. In
> order to keep the comment valid, this patch moves the *unsync* up and
> exchange the position of *role* and *gfn*.
>
> From /proc/slabinfo, it shows the size of kvm_mmu_page is 8 bytes less and
> with one more object per slap after applying this patch.
>
> # name <active_objs> <num_objs> <objsize> <objperslab>
> kvm_mmu_page_header 0 0 168 24
>
> kvm_mmu_page_header 0 0 160 25
>
> Signed-off-by: Wei Yang <richard.weiyang@xxxxxxxxx>
> ---
> arch/x86/include/asm/kvm_host.h | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 00ddb0c9e612..f1a4e520ef5c 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -280,18 +280,18 @@ struct kvm_rmap_head {
> struct kvm_mmu_page {
> struct list_head link;
> struct hlist_node hash_link;
> + bool unsync;
>
> /*
> * The following two entries are used to key the shadow page in the
> * hash table.
> */
> - gfn_t gfn;
> union kvm_mmu_page_role role;
> + gfn_t gfn;
>
> u64 *spt;
> /* hold the gfn of each spte inside spt */
> gfn_t *gfns;
> - bool unsync;
> int root_count; /* Currently serving as active root */
> unsigned int unsync_children;
> struct kvm_rmap_head parent_ptes; /* rmap pointers to parent sptes */
>
Queued, thanks.
Paolo
