Re: [Qemu-devel] [PULL 22/26] target/aarch64: optimize indirect branches

[Alex Bennée]

Alex Bennée <address@hidden> writes:

> Richard Henderson <address@hidden> writes:
>
>> From: "Emilio G. Cota" <address@hidden>
>>
>> Measurements:
>>
>> [Baseline performance is that before applying this and the previous
>> commit]
>
> Sadly this has regressed my qemu-system-aarch64 EL2 run. It was slightly
> masked by an unrelated assertion breakage which I had to fix. However
> with this patch my boot hangs spinning all 4 threads. Once reverted
> things work again.
>
> My command line:
>
>   timeout -k 1s --foreground 120s ./aarch64-softmmu/qemu-system-aarch64 
> -machine type=virt -display none -m 4096 -cpu cortex-a57 -serial mon:stdio 
> -netdev user,id=unet -device virtio-net-device,netdev=unet -drive 
> file=/home/alex/lsrc/qemu/images/jessie-arm64.qcow2,id=myblock,index=0,if=none
>  -device virtio-blk-device,drive=myblock -append "console=ttyAMA0 
> root=/dev/vda1 systemd.unit=benchmark.service" -kernel 
> /home/alex/lsrc/qemu/images/aarch64-current-linux-kernel-only.img -smp 4 
> -machine gic-version=3 -machine virtualization=true -name debug-threads=on
>
> My tree with fix and revert:
>
>   https://github.com/stsquad/qemu/tree/debug/aarch64-hang
>
> I'm investigating now.

Well this seems to be a case of hangs with -smp > 1 (which I guess was
obvious seeing as the TCG threads seem to be spinning against each
other).

--
Alex Bennée