Re: [Qemu-devel] [PATCH v2 1/5] linux-aio: queue requests that cannot be submitted

[Paolo Bonzini <pbonzini@redhat.com>]

On 16/12/2014 21:26, Paolo Bonzini wrote:
> 
>> I could reproduce this very well on a random OS image that I had around.
>>  This is raw over XFS over dm-crypt, and the image is about 75% sparse
>> (8.2G used over 35G).  I only get 1-2%, but still it's visible.
>>
>> However I can hardly reproduce it when using a partition directly:
>>
>>          old    new
>> mean     9.9565 9.9636      (+0.07%)
>> stddev   0.0405 0.0537
>> min      9.871  9.867
>> median   9.973  9.971
>> max      10.01  10.053
>> count    20     20
>>
>> I haven't tried removing layers (e.g. fully-allocated XFS image without
>> dm-crypt).
> 
> Could not reproduce it with a fully-allocated XFS image, on the contrary
> the patched QEMU is a bit faster:
> 
>         old      new
> mean    14.83325 14.82660
> stddev  0.016930 0.010328
> min     14.819   14.818
> max     14.854   14.883
> median  14.8225  14.8255
> count   20       20

Same for 50% sparse XFS image, patched QEMU a bit faster:

        old     new
Mean	8.31285 8.30625
stddev	0.03690 0.03333
min     8.277   8.276
max     8.378   8.382
median	8.292   8.2905
count   20      20