On Wed, Nov 18, 2009 at 10:59:43AM +0800, figo zhang wrote: > I am porting 24KEC soc to linux new, i have see the mips-kernel impement > cache strategy: invalid and write-back, > is it right? is it implement the write-through strategy? see in > include/asm-mips/r4kcache.h > > how i can know the kernel using which cache strategy in user space, such > as how can see the /proc system to know it? The kernel will always use cache stategy 3 for non-coherent systems and caching strategy 5 for cache coherent systems. These two select the most aggressive caching strategy on all processors and that's what gives the best performance. I think write through is just not worth thinking about it. Early 4K cores did only implement write through; later models added write-back and as the result have significantly improved performance. Minor optimizations of the cacheflush operations for write-through caches would be possible but I expect only small gains. R4kcache.h implements a bunch of helper functions that iterate over memory areas; optimizations for write-through caches should be done by the callers of these helper functions. Again, if you have write-back caches don't even think about write-though. It almost certainly less effective. Ralf
