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Subject: Re: [Qemu-devel] [PATCH] hw/vexpress: set default block type to SD
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To: Aurelien Jarno <aurelien@aurel32.net>
Cc: Peter Maydell <peter.maydell@linaro.org>, qemu-devel@nongnu.org

Il 17/03/2013 01:04, Aurelien Jarno ha scritto:
>                           | boot | install build-dep | build lm-sensors |
>   ------------------------+------+-------------------+------------------+
>   versatile               | 1:09 |             2:27  |             4:09 |
>   versatile cache=wb      | 1:08 |             2:25  |             3:44 |

Strange, cache=wb should be the default.

The real problem with SD is that it doesn't have a flush command, hence
it cannot be made safe against power losses.  But the solution is to add
support for virtio-mmio in those boards.

Paolo

>   vexpress                | 1:11 |             3:07  |             3:49 |
>   vexpress cache=wb       | 1:07 |             3:07  |             3:47 |
> 
>   Note: the install build-dep time doesn't include the download time.
> 
> So even if the two systems are not directly comparable, it shows that
> the SD card emulation is indeed slower than the hard disk one. That said
> while cache=writeback makes a difference for the versatile platform, it
> doesn't really change anything for the vexpress platform. Therefore
> forcing the users to add this option doesn't seems to be a good idea.