> -----Original Message----- > From: Thomas Monjalon [mailto:tho...@monjalon.net] > Sent: Tuesday, July 4, 2017 12:26 AM > To: Dumitrescu, Cristian <cristian.dumitre...@intel.com>; De Lara Guarch, > Pablo <pablo.de.lara.gua...@intel.com> > Cc: dev@dpdk.org; Jianbo Liu <jianbo....@linaro.org>; > jerin.ja...@caviumnetworks.com; ashwin.sek...@caviumnetworks.com > Subject: Re: [dpdk-dev] [PATCH] examples/ip_pipeline: use crc32 in hash > functions for arm64 > > 04/07/2017 01:19, Dumitrescu, Cristian: > > From: Thomas Monjalon [mailto:tho...@monjalon.net] > > > 18/05/2017 11:09, Jianbo Liu: > > > > Implement the same hash functions with crc32 on arm platform. > > > > > > > > Signed-off-by: Jianbo Liu <jianbo....@linaro.org> > > > > --- > > > > examples/ip_pipeline/pipeline/hash_func.h | 2 + > > > > examples/ip_pipeline/pipeline/hash_func_arm64.h | 245 > > > ++++++++++++++++++++++++ > > > > 2 files changed, 247 insertions(+) create mode 100644 > > > > examples/ip_pipeline/pipeline/hash_func_arm64.h > > > > > > I don't understand why this code is in an example. > > > We have some CRC code in librte_hash, librte_net and ip_pipeline. > > > Cristian, Jianbo, > > > does it make sense to move these functions somewhere else? > > > > > > > I think example apps are a great way to propose new hash functions. > > IMO we should encourage the definition/exploration of new hash > functions in our example apps. > > > > These functions are examples of how fast hash functions can be built > using special CPU instructions. > > They have much better performance than e.g. jhash, but their > > properties are largely unknown, as no rigorous study on their > > properties (such as uniform distribution) has been conducted. I have > > seen them providing good performance for the data set I have been > using, but I have no extensive data to support their maturity level. > > > > If somebody is willing to invest the effort in proving them, I would > > be more than happy to see them moved to a library like librte_hash. > > Pablo as maintainer has the choice (I think it is not the first time > > we discuss bout these hash funcs :) ) > > > > As mentioned in one of our deprecation notices, I am actively working > > (not ready for 17.8 unfortunately) to add a key mask parameter to these > functions, so more work on these hash functions is likely to take place. > > OK thanks for the explanation. > I still think we do not need to prove hash for integrating them. > I would be interested to read Pablo's opinion.
If these functions are used as hash functions, I would place them in rte_hash. The case where we placed the CRC function in librte_net was because that was not used as a hash function, so it made sense to me placing it there, but in this case, it looks like it is, so I think rte_hash is a valid place (although someone would need to integrate it with the existing CRC hash function in that library). Thanks, Pablo
