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Date: Thu, 13 Dec 2012 16:34:16 +0100
From: Jan Kiszka <jan.kiszka@siemens.com>
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Subject: Re: [Qemu-devel] [PATCH] kvm: do not flush after deleting gsi
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To: Asias He <asias@redhat.com>
Cc: Peter Maydell <peter.maydell@linaro.org>, Marcelo Tosatti <mtosatti@redhat.com>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>, "kvm@vger.kernel.org" <kvm@vger.kernel.org>, "Michael S. Tsirkin" <mst@redhat.com>

On 2012-12-13 05:55, Asias He wrote:
> Hello Michael,
> 
> On 12/12/2012 06:48 PM, Michael S. Tsirkin wrote:
>> Deleting a GSI isn't necessary: it is enough
>> to stop using it. Delay flush until an entry is used.
>>
>> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
>> ---
>>  kvm-all.c | 2 --
>>  1 file changed, 2 deletions(-)
>>
>> diff --git a/kvm-all.c b/kvm-all.c
>> index 3bc3347..fb3180d 100644
>> --- a/kvm-all.c
>> +++ b/kvm-all.c
>> @@ -991,8 +991,6 @@ void kvm_irqchip_release_virq(KVMState *s, int virq)
>>          }
>>      }
>>      clear_gsi(s, virq);
>> -
>> -    kvm_irqchip_commit_routes(s);
>>  }
>>  
>>  static unsigned int kvm_hash_msi(uint32_t data)
>>
> 
> I tried this patch with vhost-blk with qemu-1.3.0
> 6d6c9f59ca1b1a76ade7ad868bef191818f58819.
> 
> Without the drop of msix_fire_vector_notifier in msix_handle_mask_update
> hack
> Before: ~20K IOPS
> After:  ~35K IOPS
> 
> With the drop of msix_fire_vector_notifier in
> msix_handle_mask_update hack
> Before:  ~197K IOPS
> After:   ~197K IOPS
> 

Is the guest balancing the IRQ(s) between its vCPUs all the time?

Jan

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