Messages in this thread |  | | Date | Mon, 24 Feb 2014 04:51:36 -0800 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH 2/3] x86/hash: swap parameters of crc32_u32() |
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On 02/24/2014 04:41 AM, Jan Beulich wrote: >> >> So I'm guessing this hash is deliberately using the CRC32 instruction >> "backwards", which would actually make sense: an actual CRC is actually >> a pretty poor hash due to linearity. >>
OK, it really is even more confusing than that.
It does seem like the crc32 instruction really *is* commutative, which isn't something I would personally have expected at all.
Given that fact, I suspect the ordering in the DPDK is actually a bug, and that we should correct the ordering (which I would do at the call sites because it seems to make the code clearer) because it reduces the size of the loop by two instructions.
I guess I should find out how to file a bug report against DPDK too...
-hpa
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