[osg-users] CPU Performance issues with AMD 2700 vs Intel Corei7 4770S

Mon Apr 1 13:41:16 PDT 2019

I don't have any modern Apples to Apples comparisons to cite.

I do know, that if you recall, we ran into threading issues when dealing
with the massive plenoptic display IG back in 2015 or so on AMD cards, and
it needed special assistance from AMD to unclog it.

Do you know Graham Sellers at AMD? Maybe we could get some advising from
him.

On Mon, Apr 1, 2019 at 2:59 PM Robert Osfield <robert.osfield at gmail.com>
wrote:

> Hi All,
>
> I have recently got a new dev machine, a AMD2700 + Geforce 2060
> system. I wanted a quiet mulit-core system as well as to get some
> experiment working with AMD chips as I've been using Intel Corei7
> chips for the last 8 years.  The machine uses passive cooling for
> everything except the graphics card so it's soo quiet you hardly know
> it's on :-)
>
> I've begun performance testing and was expecting most improvements
> across the board for single threaded tasks, and big improvement on
> highly threaded tasks like building.   I expected this based on a
> number of online performance comparisons.  For example:
>
>
> https://cpu.userbenchmark.com/Compare/Intel-Core-i7-4770S-vs-AMD-Ryzen-7-2700/m2123vs3957
>
>     http://hwbench.com/cpus/amd-ryzen-7-2700-vs-intel-core-i7-4770s
>
> When using the OSG I'm seeing lower framerates for almost all the test
> models I regularly use, in particular the cull traversal can be 20-40%
> slower.
>
> Doing synthetic OSG + VSG scene graph creation, traversal tests shows
> the OSG 32% slower on the AMD (running osggroups from the osg2vsg
> project) while the equivalent VSG test  is ~14% faster on the AMD
> (running vsgvisitor from the vsgExamples project).
>
> Looking at the Linux perf stat utility it looks like the OSG runs for
> AMD run are hitting up against 498 context-switches for the run of
> osggroups, while the Intel just sees 24 context switches.  Branch
> misses are 0.66% on AMD vs 0.37% on Intel.  Instructions per cycle are
> all worse on the AMD too, 0.72 (AMD) vs 0.95 (Intel)
> instrictions/cycle
>
> The same equivalent tests with the VSG shows that the AMD has 56
> context switches vs 2 on the Intel.  Branch misses are also still
> higher on the AMD, but the instructions per cycle are now 2.13 (AMD)
> vs 1.96 (Intel) instructions/cycle.
>
> Another way of presenting this data, this OSG vs VSG tests runs a
> testing of creation 11 deep quad tree, traversing every node in the
> graph 10 times, then destroying the graph:
>
> VSG Intel 0.615 secs  (VSG 6.33 x faster than OSG)
> OSG Intel 3.895 secs
>
> VSG AMD 0.555 secs (VSG 9.36 x faster than OSG)
> OSG AMD 5.196 secs
>
>
> Despite the raw creation, traversals and destruction being quicker on
> the AMD with the VSG, the VSG framerates on scenes are worse on the
> AMD vs Intel though, except where the 2060's better fill rate gives it
> advantage.  Even when I take the VSG's traversals out of the equation
> and just submitted the same command graph to render each frame the
> frame rate is worse on the AMD vs Intel system, suggesting it's not
> just the slower traversals that is at issue - the Vulkan driver and
> hardware look to be struggling as well.
>
> The two systems aren't identical software wise, the Intel system in on
> Kubuntu 18.04 with gcc 7.3.0 vs Kubuntu 18.10 with gcc 8.2.0.  The
> Intel system has NVidia 396.54.09 vs AMD system with NVidia 415.27.
>
> I wouldn't have thought the OS, compile and drivers to make such stark
> differences in performance.  The VSG's lighterweight design does seem
> to help reduce the impact a bit and for some tests gives the AMD an
> advantage, but it's still overall slower on the AMD.  The OSG sees a
> huge hit on complex scenes on the AMD system.
>
> So I'm perplexed what might be going on.  The perf stat report
> suggests that the AMD is running at around 3.9-4GHz vs Intel running
> at 3.8 to 3.GHz.  The perf stat results suggests that certain
> workloads are really messing up the AMD's chip ability to efficiently
> handle the load.
>
> On one upside, the AMD's 8 cores/16 threads vs Intel's 4cores/8
> threads certainly helps when compiling the OSG, but this is small
> comfort as my job is far more focused on optimizing real-time
> rendering performance than just getting code compiled.
>
> I'd really like some feedback from the community as to what might be
> going wrong on my AMD system.  Are others seeing significantly slower
> CPU performance on AMD vs Intel for certain tasks?
>
> Any suggestions as what tests to do next?  What to tweak?
>
> Cheers,
> Robert.
>
> I have
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