lkml.org 
[lkml]   [2014]   [Feb]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 2/3] x86/hash: swap parameters of crc32_u32()
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



\
 
 \ /
  Last update: 2014-02-24 14:41    [W:0.191 / U:0.084 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site