2010-06-15 02:50:49

by Xiao Guangrong

Subject: [PATCH 6/6] KVM: MMU: trace pte prefetch

Trace pte prefetch to see what trouble we meet, if can help us to
improve the prefetch

Signed-off-by: Xiao Guangrong <[email protected]>
---
arch/x86/kvm/mmu.c | 12 +++++++++++-
arch/x86/kvm/mmutrace.h | 26 ++++++++++++++++++++++++++
arch/x86/kvm/paging_tmpl.h | 9 ++++++++-
3 files changed, 45 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 941c86b..0aaa18d 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -91,6 +91,11 @@ module_param(oos_shadow, bool, 0644);

#define PTE_PREFETCH_NUM 16

+#define PREFETCH_SUCCESS 0
+#define PREFETCH_ERR_GFN2PFN 1
+#define PREFETCH_ERR_ALLOC_MEM 2
+#define PREFETCH_ERR_READ_GPTE 3
+
#define PT_FIRST_AVAIL_BITS_SHIFT 9
#define PT64_SECOND_AVAIL_BITS_SHIFT 52

@@ -2066,11 +2071,16 @@ static void direct_pte_prefetch(struct kvm_vcpu *vcpu, u64 *sptep)
pfn = gfn_to_pfn_atomic(vcpu->kvm, gfn);
if (is_error_pfn(pfn)) {
kvm_release_pfn_clean(pfn);
+ trace_pte_prefetch(true, PREFETCH_ERR_GFN2PFN);
break;
}
- if (pte_prefetch_topup_memory_cache(vcpu))
+
+ if (pte_prefetch_topup_memory_cache(vcpu)) {
+ trace_pte_prefetch(true, PREFETCH_ERR_ALLOC_MEM);
break;
+ }

+ trace_pte_prefetch(true, PREFETCH_SUCCESS);
mmu_set_spte(vcpu, spte, ACC_ALL, ACC_ALL, 0, 0, 1, NULL,
sp->role.level, gfn, pfn, true, false);
}
diff --git a/arch/x86/kvm/mmutrace.h b/arch/x86/kvm/mmutrace.h
index 3aab0f0..1c3e84e 100644
--- a/arch/x86/kvm/mmutrace.h
+++ b/arch/x86/kvm/mmutrace.h
@@ -195,6 +195,32 @@ DEFINE_EVENT(kvm_mmu_page_class, kvm_mmu_prepare_zap_page,

TP_ARGS(sp)
);
+
+#define pte_prefetch_err \
+ {PREFETCH_SUCCESS, "SUCCESS" }, \
+ {PREFETCH_ERR_GFN2PFN, "ERR_GFN2PFN" }, \
+ {PREFETCH_ERR_ALLOC_MEM, "ERR_ALLOC_MEM" }, \
+ {PREFETCH_ERR_READ_GPTE, "ERR_READ_GPTE" }
+
+TRACE_EVENT(
+ pte_prefetch,
+ TP_PROTO(bool direct, int err_code),
+ TP_ARGS(direct, err_code),
+
+ TP_STRUCT__entry(
+ __field(bool, direct)
+ __field(int, err_code)
+ ),
+
+ TP_fast_assign(
+ __entry->direct = direct;
+ __entry->err_code = err_code;
+ ),
+
+ TP_printk("%s %s", __entry->direct ? "direct" : "no-direct",
+ __print_symbolic(__entry->err_code, pte_prefetch_err))
+);
+
#endif /* _TRACE_KVMMMU_H */

#undef TRACE_INCLUDE_PATH
diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index af4e041..64f2acb 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -331,6 +331,8 @@ static void FNAME(pte_prefetch)(struct kvm_vcpu *vcpu, u64 *sptep)
page = gfn_to_page_atomic(vcpu->kvm, sp->gfn);
if (is_error_page(page)) {
kvm_release_page_clean(page);
+ trace_pte_prefetch(false,
+ PREFETCH_ERR_READ_GPTE);
break;
}
table = kmap_atomic(page, KM_USER0);
@@ -353,11 +355,16 @@ gfn_mapping:
pfn = gfn_to_pfn_atomic(vcpu->kvm, gfn);
if (is_error_pfn(pfn)) {
kvm_release_pfn_clean(pfn);
+ trace_pte_prefetch(false, PREFETCH_ERR_GFN2PFN);
break;
}

- if (pte_prefetch_topup_memory_cache(vcpu))
+ if (pte_prefetch_topup_memory_cache(vcpu)) {
+ trace_pte_prefetch(false, PREFETCH_ERR_ALLOC_MEM);
break;
+ }
+
+ trace_pte_prefetch(false, PREFETCH_SUCCESS);
mmu_set_spte(vcpu, spte, sp->role.access, pte_access, 0, 0,
dirty, NULL, sp->role.level, gfn, pfn,
true, false);
--
1.6.1.2

2010-06-15 12:09:26

by Avi Kivity

Subject: Re: [PATCH 6/6] KVM: MMU: trace pte prefetch

On 06/15/2010 05:47 AM, Xiao Guangrong wrote:
> Trace pte prefetch to see what trouble we meet, if can help us to
> improve the prefetch
>
> Signed-off-by: Xiao Guangrong<[email protected]>
> ---
> arch/x86/kvm/mmu.c | 12 +++++++++++-
> arch/x86/kvm/mmutrace.h | 26 ++++++++++++++++++++++++++
> arch/x86/kvm/paging_tmpl.h | 9 ++++++++-
> 3 files changed, 45 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 941c86b..0aaa18d 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -91,6 +91,11 @@ module_param(oos_shadow, bool, 0644);
>
> #define PTE_PREFETCH_NUM 16
>
> +#define PREFETCH_SUCCESS 0
> +#define PREFETCH_ERR_GFN2PFN 1
> +#define PREFETCH_ERR_ALLOC_MEM 2
> +#define PREFETCH_ERR_READ_GPTE 3
> +
> #define PT_FIRST_AVAIL_BITS_SHIFT 9
> #define PT64_SECOND_AVAIL_BITS_SHIFT 52
>
> @@ -2066,11 +2071,16 @@ static void direct_pte_prefetch(struct kvm_vcpu *vcpu, u64 *sptep)
> pfn = gfn_to_pfn_atomic(vcpu->kvm, gfn);
> if (is_error_pfn(pfn)) {
> kvm_release_pfn_clean(pfn);
> + trace_pte_prefetch(true, PREFETCH_ERR_GFN2PFN);
> break;
> }
>

What about virtual addresses and gptes? They can be helpful too.

--
error compiling committee.c: too many arguments to function

2010-06-17 07:31:21

by Xiao Guangrong

Subject: Re: [PATCH 6/6] KVM: MMU: trace pte prefetch

Avi Kivity wrote:

>> @@ -2066,11 +2071,16 @@ static void direct_pte_prefetch(struct
>> kvm_vcpu *vcpu, u64 *sptep)
>> pfn = gfn_to_pfn_atomic(vcpu->kvm, gfn);
>> if (is_error_pfn(pfn)) {
>> kvm_release_pfn_clean(pfn);
>> + trace_pte_prefetch(true, PREFETCH_ERR_GFN2PFN);
>> break;
>> }
>>
>
> What about virtual addresses and gptes? They can be helpful too.
>

OK, will do it in the next version.