From: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
To: Avi Kivity <avi@redhat.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>, kvm@vger.kernel.org
Subject: Re: [PATCH v3 0/6] Optimize vcpu->requests processing
Date: Mon, 24 Sep 2012 19:16:23 +0800 [thread overview]
Message-ID: <50604107.8020105@linux.vnet.ibm.com> (raw)
In-Reply-To: <50603B58.5040703@redhat.com>
On 09/24/2012 06:52 PM, Avi Kivity wrote:
> On 09/24/2012 12:19 PM, Xiao Guangrong wrote:
>> On 09/24/2012 05:48 PM, Avi Kivity wrote:
>>> On 09/24/2012 07:55 AM, Xiao Guangrong wrote:
>>>> On 07/10/2012 01:05 AM, Avi Kivity wrote:
>>>>> Currently, any time a request bit is set (not too uncommon) we check all of them.
>>>>> This patchset optimizes the process slightly by skipping over unset bits using
>>>>> for_each_set_bit().
>>>>>
>>>>
>>>> I also notice that kvm_check_request costs lots of cpu time. What is the status
>>>> of this patchset?
>>>>
>>>
>>> I had problems getting rid of KVM_REQ_PENDING_TIMER. I'll try again.
>>>
>>> In what workloads did you see kvm_check_request()?
>>>
>>
>> Run kernbench on guest, and use perf to sample, this function is really
>> hot.
>>
>
> I don't see it at all. Westmere, 4-way guest.
>
This is the result i got on my laptop:
# ./perf report | grep "\[kvm\]"
85.59% qemu-kvm [kvm] [k] arch_local_irq_enable
0.18% qemu-kvm [kvm] [k] kvm_arch_vcpu_ioctl_run
0.10% qemu-kvm [kvm] [k] paging64_walk_addr_generic
0.10% qemu-kvm [kvm] [k] x86_decode_insn
0.08% qemu-kvm [kvm] [k] kvm_check_request
0.06% qemu-kvm [kvm] [k] apic_clear_vector
My box: i5-2540M CPU @ 2.60GHz * 4 + 4G
guest: 2 vcpu + 1G
next prev parent reply other threads:[~2012-09-24 11:16 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-09 17:05 [PATCH v3 0/6] Optimize vcpu->requests processing Avi Kivity
2012-07-09 17:05 ` [PATCH v3 1/6] KVM: Don't use KVM_REQ_PENDING_TIMER Avi Kivity
2012-07-10 8:50 ` Gleb Natapov
2012-07-10 9:13 ` Avi Kivity
2012-07-09 17:05 ` [PATCH v3 2/6] KVM: Simplify KVM_REQ_EVENT/req_int_win handling Avi Kivity
2012-07-09 17:05 ` [PATCH v3 3/6] KVM: Move mmu reload out of line Avi Kivity
2012-07-10 3:57 ` Xiao Guangrong
2012-07-10 7:48 ` Avi Kivity
2012-07-09 17:05 ` [PATCH v3 4/6] KVM: Optimize vcpu->requests checking Avi Kivity
2012-07-09 17:05 ` [PATCH v3 5/6] KVM: Reorder KVM_REQ_EVENT to optimize processing Avi Kivity
2012-07-09 17:05 ` [PATCH v3 6/6] KVM: Clean up vcpu->requests == 0 processing Avi Kivity
2012-09-24 5:55 ` [PATCH v3 0/6] Optimize vcpu->requests processing Xiao Guangrong
2012-09-24 9:48 ` Avi Kivity
2012-09-24 10:19 ` Xiao Guangrong
2012-09-24 10:52 ` Avi Kivity
2012-09-24 11:16 ` Xiao Guangrong [this message]
2012-09-24 12:12 ` Avi Kivity
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