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Commit 3ff519f2 authored by Wei Yang's avatar Wei Yang Committed by Paolo Bonzini
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KVM: x86: adjust kvm_mmu_page member to save 8 bytes 



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: default avatarWei Yang <richard.weiyang@gmail.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent bd18bffc

arch/x86/include/asm/kvm_host.h

+2 −2
Original line number Diff line number Diff line
@@ -281,18 +281,18 @@ 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 */