On Wed, 2008-10-08 at 12:40 -0500, Scott Wood wrote: > > The performance difference most likely comes from the fact that copy > to/from user can assume that the memory is cacheable, while memcpy is > occasionally used on cache-inhibited memory -- so dcbz isn't used. We > may be better off handling the alignment fault on those occasions, and > we should use dcba on chips that support it.
Note that the kernel memcpy isn't supposed to be used for non-cacheable memory. That's what memcpy_to/fromio are for. But Paul has a point that for small copies especially, the cost of the cache instructions outweigh their benefit. Cheers, Ben. _______________________________________________ Linuxppc-embedded mailing list Linuxppc-embedded@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-embedded
