On 06/15/2011 01:53 PM, Daniel Vetter wrote:

On Tue, Jun 14, 2011 at 20:30, Arnd Bergmann[off-list ref]  wrote:
   

quoted

On Tuesday 14 June 2011 18:58:35 Michal Nazarewicz wrote:
     

quoted

Ah yes, I forgot that separate regions for different purposes could
decrease fragmentation.
       

That is indeed a good point, but having a good allocator algorithm
could also solve this. I don't know too much about these allocation
algorithms, but there are probably multiple working approaches to this.
     

imo no allocator algorithm is gonna help if you have comparably large,
variable-sized contiguous allocations out of a restricted address range.
It might work well enough if there are only a few sizes and/or there's
decent headroom. But for really generic workloads this would require
sync objects and eviction callbacks (i.e. what Thomas Hellstrom pushed
with ttm).
   

Indeed, IIRC on the meeting I pointed out that there is no way to 
generically solve the fragmentation problem without movable buffers. 
(I'd do it as a simple CMA backend to TTM). This is exactly the same 
problem as trying to fit buffers in a limited VRAM area.

/Thomas