On Thu, Jan 25, 2018 at 12:59:56 +0000, Alex Bennée wrote:
> Howard Spoelstra <hsp.c...@gmail.com> writes:
(snip)
> > Recent tcg optimisations had improved processor and floating point
> > performance considerably, but that gain seems to be more than lost for
> > the floating point performance.
> >
> > Any idea what is causing this?
>
> Well we expected a little degradation but it's a bit more than I
> expected.
It's pretty bad (almost a 2X mean slowdown) for the three FP workloads
in dbt-bench:
[FWIW before is 52483b067cce, after is 00fc0c00ca9fa26]
NBench score; higher is better
Host: Intel(R) Core(TM) i7-6700K CPU @ 4.00GHz
6 +-+-----------+-------------+--------------+-------------+-----------+-+
| ***** |
| * * softfloat-before |
5 +-+.....................*...*.........******...softfloat-after.......+-+
| * * * * ****** |
| * * * * * * |
4 +-+.....................*...*.........*....*........*....*...........+-+
| * * * * * * |
3 +-+......******.........*...*.........*....*........*....*...........+-+
| * * * *##### * *#### * * |
| * * * * # * * # * *##### |
2 +-+......*....*.........*...*....#....*....*...#....*....*....#......+-+
| * * * * # * * # * * # |
| * *##### * * # * * # * * # |
1 +-+......*....*....#....*...*....#....*....*...#....*....*....#......+-+
| * * # * * # * * # * * # |
| * * # * * # * * # * * # |
0 +-+------******#####----*****#####----******####----******#####------+-+
FOURIER NEURAL NET LU DECOMPOSITION gmean
You can obtain the above on your machine (assuming /tmp/softfloat-$branch
corresponds to the before/after x86_64-linux-user binaries) with:
$ time for branch in before after; do cd $DBT_BENCH/nbench && \
taskset -c 0 /tmp/softfloat-$branch \
$DBT_BENCH/nbench/nbench -V -C$DBT_BENCH/nbench/FP.DAT \
| tee $DBT_BENCH/softfloat-$branch.nbench || break && cd -; \
done
And then plot the results with:
$ ./breakdown.pl --suite=fp --barchart softfloat-before.nbench
softfloat-after.nbench \
| $BARCHART/barchart.pl --extra-gnuplot='set term dumb 80' \
--extra-gnuplot='set title "NBench score; higher is better\nHost:
Intel(R) Core(TM) i7-6700K CPU @ 4.00GHz"' \
--extra-gnuplot="set yrange [0:]" --extra="=norotate" | gnuplot
You'll need both dbt-bench and barchart:
https://github.com/cota/dbt-bench (clone with --recursive and build nbench
first.
You can also use CROSS_COMPILE there to benchmark other linux-user targets)
https://github.com/cota/barchart
Hope that helps,
Emilio
