Re: [Qemu-devel] [PATCH 00/10] tb hash improvements

[Alex Bennée]

Emilio G. Cota <address@hidden> writes:

> This patchset is derived from my ongoing work on MTTCG, but does
> not depend on it and brings improvements that we can already
> benefit from. It applies cleanly on the current master and
> is checkpatch-clean.
>
> The key goal is to make the TB hash table faster, and while at it,
> scalable. Tested on two different host machines, the execution time
> improvement before and after this series, when booting a debian
> jessie arm image[*] with arm-softmmu, is:
>
> - Intel Xeon E5-2690: 21.2% less time
> - Intel i7-4790K: 23.5% less time
>
> This workload is particularly sensitive to TB hash performance.
> Other workloads not as sensitive might see a slight performance
> degradation with this patchset, since the hashing + lookup
> functions take now more instructions. In any case, no significant
> slowdowns should occur.
>
> The commit logs are sometimes long because I have lots of numbers
> to share.
>
> The only bits I'm not too comfortable with in this series are patches
> 2 and 5; I don't develop on Windows so I'm shooting in the dark there.
>
> Please take a look and if possible, test on workloads you care about!

Excellent stuff, will have a look this week.

>
> Thanks,
>
>               Emilio
>
> [*] taskset -c 0 arm-softmmu/qemu-system-arm -machine type=virt -nographic \
>      -smp 1 -m 4096 -netdev user,id=unet,hostfwd=tcp::2222-:22 \
>      -device virtio-net-device,netdev=unet \
>      -drive file=jessie-arm32.qcow2,id=myblock,index=0,if=none \
>      -device virtio-blk-device,drive=myblock \
>      -kernel aarch32-current-linux-kernel-only.img \
>      -append 'console=ttyAMA0 root=/dev/vda1' \
>      -name arm,debug-threads=on -smp 1 -tb-size 1024
> The image is taken from:
>   http://people.linaro.org/~alex.bennee/images/jessie-arm32.qcow2
> The image was modified to call `shutdown -h now` right after boot.
> The kernel is taken from:
>   
> http://people.linaro.org/~alex.bennee/images/aarch32-current-linux-kernel-only.img


--
Alex Bennée