On Tue, Dec 15, 2009 at 11:27 AM, Keith Whitwell <[email protected]> wrote:
> On Tue, 2009-12-15 at 01:49 -0800, Marek Olšák wrote:
>> On Tue, Dec 15, 2009 at 10:28 AM, Keith Whitwell <[email protected]> wrote:
>> > On Mon, 2009-12-14 at 16:31 -0800, Marek Olšák wrote:
>> >> On Mon, Dec 14, 2009 at 5:42 PM, Corbin Simpson
>> >> <[email protected]> wrote:
>> >> > As far as immediate verts, why don't we just add support to r300g to 
>> >> > switch
>> >> > to immediate mode for small VBOs?
>> >> >
>> >> > Posting from a mobile, pardon my terseness. ~ C.
>> >> >
>> >>
>> >> Corbin,
>> >>
>> >> that seems reasonable, and it's the reason I killed the draw_quad
>> >> function. BTW immediate mode doubles the performance in glxgears.
>> >
>> > Shouldn't gears upload its vertices one time only and then leave them
>> > resident in VRAM?
>> >
>> > Keith
>> >
>> >
>>
>> I meant the clear path with a quad using immediate mode, that made the
>> difference in comparison with a straightforward VBO path.
>
> OK, understood.
>
> I'm interested to understand why the VBO path is slow.  Is it the
> allocation of the VBO itself?  Mapping & uploading the vertices?
> Command submission (the extra reloc)?
>
> It seems to me that none of these should be taking half your time.  In
> fact, it makes me wonder if there wasn't something else going on -- eg.
> was the same buffer getting reused to hold those 4 vertices frame after
> frame, resulting in a sync when the driver tried to map the buffer?
>
> That could be happening in the state tracker or in the driver, I guess.
>
> Keith
>

Yes, the same buffer was getting reused every frame causing sync when
mapping the buffer. However, it will no longer be an issue once
immediate mode gets implemented. Using DONT_WAIT would probably also
help here.

Please, could you possibly look at the patches I sent to you
approximately 16 hours ago? (there are 7 of them)

Marek

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