On Mon, Dec 1, 2014 at 9:42 AM, Austin S Hemmelgarn > Except most of the CPU optimized hashes aren't crypto hashes (other than the > various SHA implementations). Furthermore, I've actually tested the speed > of a generic CRC32c implementation versus SHA-1 using the SHA instructions > on an UltraSPARC processor, and the difference ammounts to a few > microseconds in _favor_ of the optimized crypto hash; and I've run the math > for every other ISA that has instructions for computing SHA hashes (I don't > have the hardware for any of the others), and expect similar results for > those as well.
I think the confusion here is that I am talking about 128-bit and 256-bit hashes, which is what you would choose for filesystem checksums if you want to have extremely strong collision resistance (eg., you could also use it for dedup). You seem to be talking about 32-bit (and maybe 64-bit) hashes. The speed difference between crypto 128- and 256-bit hashes and non-crypto equivalents that I have mentioned is an order of magnitude or more. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
