EXA and MigrationHeuristic

[Juliusz Chroboczek]

> "greedy" is faster than "always" in some cases because it's quite
> conservative about migrating pixmaps offscreen. Any single low level
> operation can only be accelerated if all pixmaps involved are offscreen,
> so this results in fewer operations being accelerated, thereby avoiding
> migration overhead for operations that can't be accelerated for other
> reasons.

Let me change the emphasis.  Main-memory pixmaps are moderately fast
for all operations.  Off-screen pixmaps are very fast for some
operations, and glacially slow for others.

It seems to me that a migration heuristic that prefers main memory is
preferable in the general case.


                                        Juliusz