Hi,
On 11/01/11 22:38, Tim Moore wrote:
On Tue, Jan 11, 2011 at 6:01 PM, Robert Osfield
<[email protected] <mailto:[email protected]>> wrote:
Hi Tim,
Thanks for the patch, now merged and submitted to svn/trunk.
What configuration of the viewer + osgEarth did you seen the
performance drop? Was it a consistent performance drop? Anything in
particular that led you to suspect ThreadSafeQueue as problem?
It was a very simple osgEarth example: gdal_tiff.earth, which has a
couple of levels of images and geometry. The default threading mode on
this 2 processor laptop is DrawThreadPerContext, and it was very
noticeable that the performance was 15 fps, as opposed to 60 fps in
SingleThreaded mode. I interrupted the program with gdb a few times and
found the draw thread waiting for a new SceneView, so I started looking
at the queues. There is something else lurking out there: occasionally
(about one time in 30) I see the same slow down, but before this change
it was very consistent. So, I can convince myself that the change helps,
but maybe it's an accident of thread timing and such that is giving the
improvement. I wish I had better tools for locating thread latency in
Linux...
I've not tried many of these (if only I had time), but maybe...
http://www.realtimerendering.com/blog/tools-tools-tools/
http://valgrind.org/docs/manual/hg-manual.html
http://0pointer.de/blog/projects/mutrace.html
regards
jp
I'm curious as the cause of the lack of multi-context scaling is
rather perplexing right now so the more background knowledge about
what type of things look to be problematic and why is useful.
I've found that the NVidia driver is taking a lock on every major call,
such as a texture bind, program application, etc. I don't know who is
protecting what and if there is actual contention between draw threads.
I see that there is a race in OpenThreads::Block::set(). I haven't tried
fixing it yet to see if notifications are being dropped.
Tim
Cheers,
Robert.
On Wed, Jan 5, 2011 at 10:42 PM, Tim Moore <[email protected]
<mailto:[email protected]>> wrote:
> Hi,
> This patch fixes a race condition in Renderer::ThreadSafeQueue
that was
> causing some notifications of available SceneView objects to be
missed. I
> saw a very noticeable performance problem (60 fps -> 8 fps) in
> DrawThreadPerContext mode in an osgEarth application before this
patch. I
> had high hopes that this change might fix the much-discussed
multiple GPU
> problem; no such luck, but I think the root cause of that is
probably a
> similar threading issue.
> Tim
>
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>
>
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