Re: [Chromium-users] Tilesort generates needed network traffic?

[Brian P. <bri...@tu...>]

James Supancic wrote:
>  >Why do you say that?  Line 87 of tilesortspu_swap.c is a call to
>  >crPackSwapBuffers().
> 
> Opps, I was mis-reading my debuger ouptut.
> 
> I am also a bit confused about this.  tilesortspu_SwapBuffer calls this 
> function:
> void PACK_APIENTRY crPackSwapBuffers( GLint window, GLint flags )
> {
>     GET_PACKER_CONTEXT(pc);
>     unsigned char *data_ptr;
>     (void) pc;
>     GET_BUFFERED_POINTER( pc, 16 );
>     WRITE_DATA( 0, GLint, 16 );
>     WRITE_DATA( 4, GLenum, CR_SWAPBUFFERS_EXTEND_OPCODE );
>     WRITE_DATA( 8, GLint, window );
>     WRITE_DATA( 12, GLint, flags );
>     WRITE_OPCODE( pc, CR_EXTEND_OPCODE );
> }
> 
> to put the SwapBuffers command into the buffer, and it eventually 
> invokes tilesortspuSendServerBufferThread once per server to send the 
> buffers?

Right.


> In the tilesortspuSendServerBufferThread function it looks as if each 
> server has its own buffer, but crPackSwapBuffers looks like it is just 
> writting to one buffer? Am I missing something? Does crPackSwapBuffers 
> get called more than once? Is it somehow packing multiple buffers? Is 
> there a global buffer that is somehow combined with server specific 
> buffers at time of send?

In the case of the loop over tilesortspuSendServerBuffer(), we're 
sending the contents of the same buffer to all servers.

There's a number of different packing buffers in the Tilesort SPU. 
Some hold geometry commands and are sent to one or more servers.  Some 
buffers contain state-change commands and are sent to individual servers.

The code is pretty complicated since it's evolved a lot over the 
years.  It would be nice to overhaul it someday.

-Brian