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Date: Thu, 13 Dec 2012 12:55:51 +0800
From: Asias He <asias@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH] kvm: do not flush after deleting gsi
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To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jan Kiszka <jan.kiszka@siemens.com>, Marcelo Tosatti <mtosatti@redhat.com>, qemu-devel@nongnu.org, kvm@vger.kernel.org, Peter Maydell <peter.maydell@linaro.org>

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

-- 
Asias