linux-kernel - Re: [PATCH] KVM: trace the events of mmu

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Message-ID: <50362257.6060006@linux.vnet.ibm.com>
Date:	Thu, 23 Aug 2012 20:30:15 +0800
From:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
To:	Marcelo Tosatti <mtosatti@...hat.com>
CC:	Avi Kivity <avi@...hat.com>, LKML <linux-kernel@...r.kernel.org>,
	KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH] KVM: trace the events of mmu_notifier

On 08/23/2012 05:24 PM, Marcelo Tosatti wrote:
> On Tue, Aug 21, 2012 at 05:51:35PM +0800, Xiao Guangrong wrote:
>> mmu_notifier is the interface to broadcast the mm events to KVM, the
>> tracepoints introduced in this patch can trace all these events, it is
>> very helpful for us to notice and fix the bug caused by mm
>>
>> Signed-off-by: Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
>> ---
>>  include/trace/events/kvm.h |  121 ++++++++++++++++++++++++++++++++++++++++++++
>>  virt/kvm/kvm_main.c        |   19 +++++++
>>  2 files changed, 140 insertions(+), 0 deletions(-)
>>
>> diff --git a/include/trace/events/kvm.h b/include/trace/events/kvm.h
>> index 7ef9e75..a855ff9 100644
>> --- a/include/trace/events/kvm.h
>> +++ b/include/trace/events/kvm.h
>> @@ -309,6 +309,127 @@ TRACE_EVENT(
>>
>>  #endif
>>
>> +#if defined(CONFIG_MMU_NOTIFIER) && defined(KVM_ARCH_WANT_MMU_NOTIFIER)
>> +DECLARE_EVENT_CLASS(mmu_notifier_address_class,
>> +
>> +	TP_PROTO(struct kvm *kvm, unsigned long address),
>> +
>> +	TP_ARGS(kvm, address),
>> +
>> +	TP_STRUCT__entry(
>> +		__field(struct kvm *, kvm)
>> +		__field(unsigned long, address)
>> +	),
>> +
>> +	TP_fast_assign(
>> +		__entry->kvm = kvm;
>> +		__entry->address = address;
>> +	),
>> +
>> +	TP_printk("kvm %p address %lx", __entry->kvm, __entry->address)
> 
> 
> Perhaps the pointer was useful for debugging, but otherwise, i don't
> think it should be printed.

But this is the only information to identify the guest if may guest
are running.

> 
>> +	TP_ARGS(kvm, address, pte),
>> +
>> +	TP_STRUCT__entry(
>> +		__field(struct kvm *, kvm)
>> +		__field(unsigned long, address)
>> +		__field(unsigned long, pte)
>> +	),
>> +
>> +	TP_fast_assign(
>> +		__entry->kvm = kvm;
>> +		__entry->address = address;
>> +		__entry->pte = pte.pte;
>> +	),
>> +
>> +	TP_printk("kvm %p address %lx pte %lx", __entry->kvm, __entry->address,
>> +		  __entry->pte)
> 
> The pte bits can be spelled out? (see __print_symbolic).

This tracepoint is put in kvm.h which can be used on different architectures
which have different pte decode. I will try to find a way to show more
readable format.

> 
>>  	spin_lock(&kvm->mmu_lock);
>>
>> +	trace_kvm_mmu_notifier_clear_flush_young(kvm, address);
>> +
>>  	young = kvm_age_hva(kvm, address);
>>  	if (young)
>>  		kvm_flush_remote_tlbs(kvm);
>> @@ -394,6 +407,9 @@ static int kvm_mmu_notifier_test_young(struct mmu_notifier *mn,
>>
>>  	idx = srcu_read_lock(&kvm->srcu);
>>  	spin_lock(&kvm->mmu_lock);
>> +
>> +	trace_kvm_mmu_notifier_test_young(kvm, address);
>> +
> 
> can print young information?

Okay, will do it in next version.

Thanks for your review, Marcelo!

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