>>>>>> "Andi" == Andi Kleen <andi@xxxxxxxxxxxxxx> writes: > >>> On Westmere and beyond it is possible to accelerate generic CRC >>> calculation using the PCLMULQDQ operation. There are many of our CRC > > Andi> Faster than the lookup table? That's hard to believe. > > Using PCLMULQDQ you can parallelize the calculation. You can even boost > hw CRC32C performance that way. > > http://download.intel.com/design/intarch/papers/323405.pdf > > http://download.intel.com/design/intarch/papers/323102.pdf Doesn't have any performance numbers. You need to keep in mind that PCLMULQDQ uses FPU state, so any speedup for the kernel must be large enough to amortize the cost of saving the FPU state. Typically that only works out for quite large buffers, but kernel buffers are relatively small. For the ext4 metadata a better approach is probably some sort of incremental CRC, or possibly separate CRCs for very commonly changed fields. When I looked at this most changes were only for small fields. -Andi -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
