3D Demo at ARM
zach.pfeffer at linaro.org
Wed Aug 17 17:04:20 UTC 2011
On 17 August 2011 04:12, Dave Martin <dave.martin at linaro.org> wrote:
> On Tue, Aug 16, 2011 at 7:14 PM, Zach Pfeffer <zach.pfeffer at linaro.org> wrote:
>> Thanks for the notes. As you say there are many, many things that can
>> affect this demo. What notes like this really underscore is the
>> importance of staying up-to-date. This demo is more about the
>> macroscopic effects from tip support than anything else. We do have
>> some more specific benchmark numbers at:
> If we're confident that the benchmark produces results of a
> trustworthy quality, then that's fine. I don't know this benchmark in
> detail, so I can't really judge, other than that the results look a
> bit odd.
> But a performance comparison where the "fast" board occasionally
> produces worse numbers than "slow" board does rather undermine the
> argument -- when a given person comes to look at the demo and watches
> a single run then that result may be the only thing they see, and they
> may take away a negative impression. Explanations can be made of
> course, but the point of a demo is that seeing is believing.
Sure. I have seen it be slower in a few instances.
> There might be ways to modify the demo to show the comparison a bit
> better though. Someone (kiko?) suggested running the rendering
> continuously throughout the day, with a total frame count displayed
> for each board or something. This could show more effectively the
> long-term average performance, and would smooth out the impact of
> short-term OS housekeeping tasks and other junk which may execute
> randomly during the demo.
Yeah, that sounds good. Most of our improvements are against the code
running on the main core so anything compute bound should work.
Perhaps we could do a fractal demo and throw up a realtime, slightly
transparent, dashboard that showed the results as the demo free ran.
>> On 13 August 2011 06:07, Dechesne, Nicolas <n-dechesne at ti.com> wrote:
>>> On Thu, Aug 11, 2011 at 12:56 AM, Zach Pfeffer <zach.pfeffer at linaro.org>
>>>> The demo consisted of two identical PandaBoards with identical SD
>>>> cards running the 3D benchmark of 0xbench using software 3D to amplify
>>>> compiler and kernel improvements. 0xbench is a benchmarking program we
>>>> ship with our Android images from 0xlab. Each build ran the same
>>>> Android userspace, 2.3.4, but one was using the 2.6.36 Linux kernel
>>>> and GCC 4.4 from the stock AOSP distribution and one was using an
>>>> upgraded Linaro 3.0 Linux kernel with Linaro GCC 4.5. We ran the board
>>>> in 640x480 mode so that we wouldn't be memory bound.
>>> have you checked all clock configuration and ensure they are the same? .36
>>> seems quite old (in the pandaboard lifetime) and i would suspect the CPU and
>>> memory clocks could be wrong compared to the linaro 3.0 (which I tried
>>> recently and which seems to have the right config). there are all bunch of
>>> kernel settings that can largely impact your demo like cache settings for
>>> since DVFS is not enabled in both kernel I believe, the clock setting might
>>> very well come from the bootloaders. which xloader and uboot are you using
>>> in both cases?
>>> have you tried to run the same demo with the exact same bootloaders and
>>> kernel? just a different user space built with 2 different compilers? I
>>> don't expect performances improvements to come from the kernel anyways (at
>>> least for such benchmark) that way you are sure you are really looking at
>>> GCC improvements. similarly you can run the same user space with both
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> Dave Martin <dave.martin at linaro.org>
> Linaro Kernel Working Group
> http://www.linaro.org/ -- Open source software for ARM SoCs
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