Re: [PATCH v3 10/15] KVM: MMU: allocate shadow pages from slab

Gleb Natapov
2013-10-24T09:19:13Z

On Wed, Oct 23, 2013 at 09:29:28PM +0800, Xiao Guangrong wrote:
> Allocate shadow pages from slab instead of page-allocator, frequent
> shadow page allocation and free can be hit in the slab cache, it is
> very useful for shadow mmu
>
> Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
> ---
> arch/x86/include/asm/kvm_host.h | 3 ++-
> arch/x86/kvm/mmu.c | 46 ++++++++++++++++++++++++++++++++++-------
> 2 files changed, 41 insertions(+), 8 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 5cbf316..df9ae10 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -389,6 +389,7 @@ struct kvm_vcpu_arch {
> struct kvm_mmu *walk_mmu;
>
> struct kvm_mmu_memory_cache mmu_pte_list_desc_cache;
> + struct kvm_mmu_memory_cache mmu_shadow_page_cache;
> struct kvm_mmu_memory_cache mmu_page_cache;
> struct kvm_mmu_memory_cache mmu_page_header_cache;
>
> @@ -946,7 +947,7 @@ static inline struct kvm_mmu_page *page_header(hpa_t shadow_page)
> {
> struct page *page = pfn_to_page(shadow_page >> PAGE_SHIFT);
>
> - return (struct kvm_mmu_page *)page_private(page);
> + return (struct kvm_mmu_page *)(page->mapping);
Why?

> }
>
> static inline u16 kvm_read_ldt(void)
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index f3ae74e6..1bcc8c8 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -178,6 +178,7 @@ struct kvm_shadow_walk_iterator {
> __shadow_walk_next(&(_walker), spte))
>
> static struct kmem_cache *pte_list_desc_cache;
> +static struct kmem_cache *mmu_shadow_page_cache;
> static struct kmem_cache *mmu_page_header_cache;
> static struct percpu_counter kvm_total_used_mmu_pages;
>
> @@ -746,7 +747,14 @@ static int mmu_topup_memory_caches(struct kvm_vcpu *vcpu)
> GFP_KERNEL);
> if (r)
> goto out;
> - r = mmu_topup_memory_cache_page(&vcpu->arch.mmu_page_cache, 8);
> +
> + r = mmu_topup_memory_cache(&vcpu->arch.mmu_shadow_page_cache,
> + mmu_shadow_page_cache, 4,
> + GFP_KERNEL);
> + if (r)
> + goto out;
> +
> + r = mmu_topup_memory_cache_page(&vcpu->arch.mmu_page_cache, 4);
> if (r)
> goto out;
> r = mmu_topup_memory_cache(&vcpu->arch.mmu_page_header_cache,
> @@ -760,6 +768,8 @@ static void mmu_free_memory_caches(struct kvm_vcpu *vcpu)
> {
> mmu_free_memory_cache(&vcpu->arch.mmu_pte_list_desc_cache,
> pte_list_desc_cache);
> + mmu_free_memory_cache(&vcpu->arch.mmu_pte_list_desc_cache,
> + mmu_shadow_page_cache);
> mmu_free_memory_cache_page(&vcpu->arch.mmu_page_cache);
> mmu_free_memory_cache(&vcpu->arch.mmu_page_header_cache,
> mmu_page_header_cache);
> @@ -1675,12 +1685,28 @@ static inline void kvm_mod_used_mmu_pages(struct kvm *kvm, int nr)
> percpu_counter_add(&kvm_total_used_mmu_pages, nr);
> }
>
> +static void set_page_header(struct kvm_mmu_page *sp)
> +{
> + struct page *page = virt_to_page(sp->spt);
> +
> + WARN_ON(page->mapping);
> + page->mapping = (struct address_space *)sp;
> +}
> +
> +static void clear_page_header(struct kvm_mmu_page *sp)
> +{
> + struct page *page = virt_to_page(sp->spt);
> +
> + page->mapping = NULL;
> +}
> +
> static void kvm_mmu_free_page(struct kvm_mmu_page *sp)
> {
> ASSERT(is_empty_shadow_page(sp->spt));
> hlist_del(&sp->hash_link);
> list_del(&sp->link);
> - free_page((unsigned long)sp->spt);
> + clear_page_header(sp);
> + kmem_cache_free(mmu_shadow_page_cache, sp->spt);
> if (!sp->role.direct)
> free_page((unsigned long)sp->gfns);
> kmem_cache_free(mmu_page_header_cache, sp);
> @@ -1719,10 +1745,10 @@ static struct kvm_mmu_page *kvm_mmu_alloc_page(struct kvm_vcpu *vcpu,
> struct kvm_mmu_page *sp;
>
> sp = mmu_memory_cache_alloc(&vcpu->arch.mmu_page_header_cache);
> - sp->spt = mmu_memory_cache_alloc(&vcpu->arch.mmu_page_cache);
> + sp->spt = mmu_memory_cache_alloc(&vcpu->arch.mmu_shadow_page_cache);
> if (!direct)
> sp->gfns = mmu_memory_cache_alloc(&vcpu->arch.mmu_page_cache);
> - set_page_private(virt_to_page(sp->spt), (unsigned long)sp);
> + set_page_header(sp);
>
> /*
> * The active_mmu_pages list is the FIFO list, do not move the
> @@ -2046,12 +2072,13 @@ static void mmu_sync_children(struct kvm_vcpu *vcpu,
> }
> }
>
> -static void init_shadow_page_table(struct kvm_mmu_page *sp)
> +static void init_shadow_page_table(void *p)
> {
> + u64 *sptp = (u64 *)p;
> int i;
>
> for (i = 0; i < PT64_ENT_PER_PAGE; ++i)
> - sp->spt[i] = 0ull;
> + sptp[i] = 0ull;
> }
>
> static void __clear_sp_write_flooding_count(struct kvm_mmu_page *sp)
> @@ -2137,7 +2164,6 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
> account_shadowed(vcpu->kvm, gfn);
> }
> sp->mmu_valid_gen = vcpu->kvm->arch.mmu_valid_gen;
> - init_shadow_page_table(sp);
> trace_kvm_mmu_get_page(sp, true);
> return sp;
> }
> @@ -4683,6 +4709,12 @@ int kvm_mmu_module_init(void)
> if (!pte_list_desc_cache)
> goto nomem;
>
> + mmu_shadow_page_cache = kmem_cache_create("mmu_shadow_page_cache",
> + PAGE_SIZE, PAGE_SIZE, 0,
> + init_shadow_page_table);
> + if (!mmu_shadow_page_cache)
> + goto nomem;
> +
> mmu_page_header_cache = kmem_cache_create("kvm_mmu_page_header",
> sizeof(struct kvm_mmu_page),
> 0, 0, NULL);
> --
> 1.8.1.4

--
Gleb.