Avi Kivity wrote: > On 07/06/2010 01:49 PM, Xiao Guangrong wrote: >> Introduce this function to topup prefetch cache >> >> >> >> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c >> index 3dcd55d..cda4587 100644 >> --- a/arch/x86/kvm/mmu.c >> +++ b/arch/x86/kvm/mmu.c >> @@ -89,6 +89,8 @@ module_param(oos_shadow, bool, 0644); >> } >> #endif >> >> +#define PTE_PREFETCH_NUM 16 >> > > Let's make it 8 to start with... It's frightening enough. > > (8 = one cache line in both guest and host)
Umm, before post this patchset, i have done the draft performance test for different prefetch distance, and it shows 16 is the best distance that we can get highest performance. > >> @@ -316,15 +318,16 @@ static void update_spte(u64 *sptep, u64 new_spte) >> } >> } >> >> -static int mmu_topup_memory_cache(struct kvm_mmu_memory_cache *cache, >> - struct kmem_cache *base_cache, int min) >> +static int __mmu_topup_memory_cache(struct kvm_mmu_memory_cache *cache, >> + struct kmem_cache *base_cache, int min, >> + int max, gfp_t flags) >> { >> void *obj; >> >> if (cache->nobjs>= min) >> return 0; >> - while (cache->nobjs< ARRAY_SIZE(cache->objects)) { >> - obj = kmem_cache_zalloc(base_cache, GFP_KERNEL); >> + while (cache->nobjs< max) { >> + obj = kmem_cache_zalloc(base_cache, flags); >> if (!obj) >> return -ENOMEM; >> cache->objects[cache->nobjs++] = obj; >> @@ -332,6 +335,20 @@ static int mmu_topup_memory_cache(struct >> kvm_mmu_memory_cache *cache, >> return 0; >> } >> >> +static int mmu_topup_memory_cache(struct kvm_mmu_memory_cache *cache, >> + struct kmem_cache *base_cache, int min) >> +{ >> + return __mmu_topup_memory_cache(cache, base_cache, min, >> + ARRAY_SIZE(cache->objects), GFP_KERNEL); >> +} >> + >> +static int pte_prefetch_topup_memory_cache(struct kvm_vcpu *vcpu) >> +{ >> + return __mmu_topup_memory_cache(&vcpu->arch.mmu_rmap_desc_cache, >> + rmap_desc_cache, PTE_PREFETCH_NUM, >> + PTE_PREFETCH_NUM, GFP_ATOMIC); >> +} >> + >> > > Just make the ordinary topup sufficient for prefetch. If we allocate > too much, we don't lose anything, the memory remains for the next time > around. > Umm, but at the worst case, we should allocate 40 items for rmap, it's heavy for GFP_ATOMIC allocation and holding mmu_lock. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html