Re: Sudden slowdown of ARM emulation in master

[Philippe Mathieu-Daudé]

On 2/26/20 9:41 AM, Peter Maydell wrote:
> On Tue, 25 Feb 2020 at 23:08, Niek Linnenbank <address@hidden> wrote:
>
> > Just now I was working on some small fixes for the cubieboard machine and 
> > rebasing my Allwinner H3 branches.
> > While doing some testing, I noticed that suddenly the machines were much slower 
> > than before.
> > I only see this happening when I rebase to this commit:
> >     ca6155c0f2bd39b4b4162533be401c98bd960820 ("Merge tag 'patchew/address@hidden' of 
> > https://github.com/patchew-project/qemu into HEAD")
>
> Yeah, I noticed a slowdown yesterday as well, but haven't tracked it down
> as yet. The first thing would be to do a git bisect to try to narrow
> down what commit caused it.

My guess: biggest chunk of memory is the DRAM, registered as "fast RAM" 
by QEMU, but the SoCs provide SRAM which is supposed to be faster. Not 
anymore with QEMU. And Linux try to use the SRAM when possible.