On 17/12/2014 13:34, Paolo Bonzini wrote:
>
>
> 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
Today I cannot reproduce it even on the original testcase:
old new
mean 9.64175 9.60935
stddev 0.15211 0.11117
min 9.445 9.454
max 10.102 9.835
median 9.64 9.6205
count 20 20
Some notes:
1) do you have Fam's io_get_events patch? I don't, and the tests
probably should be done with it.
2) "qemu-img bench" probably could also be changed to use AioContext
directly instead of going through GMainLoop. That said, there is some
low-hanging fruit for GMainLoop that I'll shortly send a patch for.
3) bench_cb does this:
b->sector += b->bufsize;
Should it shift right by >> BDRV_SECTOR_BITS? Or is it intended to do
the equivalent of a random read benchmark?
Paolo
