Re: gEDA-user: PCB+GL notes on VBOs

["Bert Timmerman" <bert.timmerman@xxxxxxxxx>]

Hi all, 

> -----Original Message-----
> From: geda-user-bounces@xxxxxxxxxxxxxx 
> [mailto:geda-user-bounces@xxxxxxxxxxxxxx] On Behalf Of Richard Barlow
> Sent: Friday, November 12, 2010 3:00 PM
> To: gEDA user mailing list
> Subject: Re: gEDA-user: PCB+GL notes on VBOs
> 
> Hi,
> 
> On Fri, 2010-11-05 at 09:46 +0000, Peter Clifton wrote:
> > 1. My VBOs and arrays are pretty large buffers, to fit lots 
> of geometry.
> ...
> > So.. we have a large buffer. That is a large chunk of 
> graphics memory 
> > to be requesting all the time. I think that contributes if the card 
> > doesn't have a decent chunk free yet.
> 
> I did a little bit of investigation and I suspect this is the 
> culprit to everyone's poor performance.
> 
> I ran the power-hw board on my machine and achieved around 85FPS.
> Felipe ran the same board on his machine and achieved around 18FPS.
> 
> My graphics card has 1GB of VRAM, Felipe's has 256MB (I 
> couldn't easily compare this to other people's results as not 
> many people said what card/driver they were using). I have 
> tried quadrupling the size of the VBO and now get around 
> 17FPS, which is considerably less than a quarter of my 
> previous result and almost exactly the same as what Felipe got.
> 
> I would say that this indicates that the large size of the 
> buffer is to blame for the speed problems if everyone else 
> has cards with ~256MB of VRAM and therefore the driver is 
> having to swap out part of the buffer into system memory.
> 
> 
> NB: I ran the above test with the larger buffer on code 
> before commit 0fa243b4bf which seems to change how the buffer 
> allocation is performed.
> I have tried running it with the quadrupled buffer on the 
> head of that branch and see no drop in performance any more. 
> I still think my analysis stands though if people don't have 
> enough VRAM to hold the size of the buffer used by the 
> power-hw board. 
> 
> Richard
> 

FWIW, a large amount of graphics memory is one thing, my 256 Mb graphics
memory is shared memory which is contributing to the total performance
equation.

I still have to start the prcess of fine tuning modelines and BIOS to get
the max performance wrung out of the HW.

Kind regards,

Bert Timmerman.




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