[Spice-devel] [SPAM] Re: QUIC Image Decompression Method takes much time

[Frediano Ziglio]

> 
> On Mon, Jan 11, 2016 at 04:37:32PM +0530, Ritesh Prajapati wrote:
> > Hi Christophe,
> > 
> >     Do you know that by adding *"-mno-unaligned-access"* flag into CFLAGS
> >     of
> > MakeFile will decrease time to decompress Image through QUIC method in our
> > ARM based A20 SoC board? Does that flag will impact anything from
> > performance perspective?
> 
> No I don't know if this will help or not. IF you read through this
> thread, you'll see that this flag has been tested (server-side though),
> and did not seem to make a difference (iirc).
> 
> Christophe
> 

The A20 is a Cortex processor (A7 or at least A6) which implements unaligned
access.
Anton is using (http://lists.freedesktop.org/archives/spice-devel/2015-October/022797.html)
an AST2150 (http://drivers.softpedia.com/get/GRAPHICS-BOARD/ASPEED/ASPEED-AST2150-Graphics-Driver-601097-for-Server-2008-R2-64-bit.shtml)
which is based on ARM9 which is a V5 (http://www.arm.com/products/processors/classic/arm9).
See also http://www.heyrick.co.uk/armwiki/Unaligned_data_access.

I'm trying to use Qemu to reproduce the issue however even using arm926 (which is a
v5) behave like an arm v6 (do unaligned access). I think this is a misemulation on Qemu
side (I'm using https://people.debian.org/~aurel32/qemu/armel/ and Qemu from Fedora 22).
According to http://www.mjmwired.net/kernel/Documentation/arm/mem_alignment I should
able to get some warning but nothing happen and data readed are not following v5 behavior.

Frediano