Re: [Qemu-devel] qemu-user-linux: how could I measure performance for aarch64 and arm?

[Peter Maydell]

On Sun, 13 Jan 2019 at 07:31, Matwey V. Kornilov
<address@hidden> wrote:
>
> пт, 11 янв. 2019 г. в 22:24, Matwey V. Kornilov <address@hidden>:
> > Indeed, qemu-arm from master runs for 4 minutes where 2.11 runs for 2
> > hours for me. It is impressive improvement.
>
> I've managed to bisected the first good (fast) commit:
>
> commit 2a53535af471f4bee9d6cb5b363746b8d5ed21dd
> Author: Luke Shumaker <address@hidden>
> Date:   Thu Dec 28 13:08:13 2017 -0500
>
>     linux-user: init_guest_space: Try to make ARM space+commpage continuous
>
> Though I am not sure, how does it help.

Oh, right, you were running into that bug:
https://bugs.launchpad.net/qemu/+bug/1740219

The problem was that we were not putting things in the right
place in memory for 32-bit Arm guest binaries in particular,
which could mean that we spent a long time trying a lot of
placements for memory mappings that failed instead of getting
an arrangement that worked first time. This meant startup
time for the guest binary was pretty slow. I guess your
application does a lot of exec()ing of new processes?

thanks
-- PMM