On Tue, Jun 14, 2011 at 20:30, Arnd Bergmann arnd@arndb.de wrote:
On Tuesday 14 June 2011 18:58:35 Michal Nazarewicz wrote:
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).
So if this is only a requirement on very few platforms and can be cheaply fixed with multiple cma allocation areas (heck, we have slabs for the same reasons in the kernel), it might be a sensible compromise. -Daniel