From: "Dumitrescu, Cristian" <cristian.dumitrescu@intel.com>
To: Thomas Monjalon <thomas.monjalon@6wind.com>,
"De Lara Guarch, Pablo" <pablo.de.lara.guarch@intel.com>
Cc: "Singh, Jasvinder" <jasvinder.singh@intel.com>,
"dev@dpdk.org" <dev@dpdk.org>,
"Doherty, Declan" <declan.doherty@intel.com>
Subject: Re: [dpdk-dev] [PATCH v2 1/2] librte_net: add crc init and compute APIs
Date: Wed, 15 Mar 2017 19:09:25 +0000 [thread overview]
Message-ID: <3EB4FA525960D640B5BDFFD6A3D89126527609CA@IRSMSX108.ger.corp.intel.com> (raw)
In-Reply-To: <6450918.dWRLMxV3EZ@xps13>
> -----Original Message-----
> From: Dumitrescu, Cristian
> Sent: Wednesday, March 15, 2017 7:04 PM
> To: 'Thomas Monjalon' <thomas.monjalon@6wind.com>; De Lara Guarch,
> Pablo <pablo.de.lara.guarch@intel.com>
> Cc: Singh, Jasvinder <jasvinder.singh@intel.com>; dev@dpdk.org; Doherty,
> Declan <declan.doherty@intel.com>
> Subject: RE: [dpdk-dev] [PATCH v2 1/2] librte_net: add crc init and compute
> APIs
>
> ... <snip>
>
> > > > > > I think it should be in librte_hash.
> > > > > >
> > > > > > Please check lib/librte_hash/rte_hash_crc.h
> > > > >
> > > > > Is it good to include payload crc calculation in hash library as I see all
> > hash
> > > > related functionality there?
> > > >
> > > > I think yes. Pablo?
> > >
> > > I think this doesn't belong in the hash library. These new functions
> calculate
> > CRC, but not as a hash function.
> >
> > Can't we say that a CRC is a hash? What is a hash?
> > A function generating the same output bytes from given input bytes.
> >
> > I think you must separate hash functions and hash table management.
> >
>
> The fact that CRC32 instruction is opportunistically used to compute a hash
> digest/signature for load balancing (affinity-based) or hash tables (flow
> tables, ARP cache, etc) does not mean that all the code that uses CRC32
> instruction should be placed in librte_hash.
>
> The purpose of the hash functions in librte_hash is to compute a
> digest/signature for a given array of bytes (the key) as fast as possible. Any
> hash function that produces a hash signature with good uniform distribution
> in a small amount of cycles belongs here, including those opportunistically
> using specialized CPU instructions such as CRC32 (or XOR, AESNI, etc).
>
> The code proposed in this patch is used to compute packet fields for various
> protocols that have a CRC field, such as FCS of Ethernet frames, etc.
> according to the relevant standard (IEEE 802, others). It is an utility to be used
> for implementing protocol-level functionality for various protocols from the
> network stack, similar to e.g. IP or UDP checksum. If we were to add an IP or
> UDCP checksum calculator, would you put it in librte_hash?
>
> The code from this patch is never going to be used to compute a fast
> signature/digest. Typically this CRC is computed over the entire frame/packet
> rather than just selected fields from the packet representing the application-
> specific flow key. Also note that the signature produced by CRC32 hash
> function from librte_hash is actually not the correct Cyclic Redundancy Check
> of that array of bytes (or, for math guys, of the associated polynomial), it is
> just a partial/intermediate value.
>
> Therefore, I suggest placing this code into: librte_ether (given that it can be
> used to compute Ethernet FCS), or librte_net, or librte_crc. Definitely not in
> librte_hash.
>
Sorry, my bad on librte_ether: the rte_ether.h where Ethernet frame is defined is located in librte_net, not librte_ether, so librte_ether should not be on the above list. Therefore, my suggestion is: librte_net or a new library librte_crc.
> Regards,
> Cristian
next prev parent reply other threads:[~2017-03-15 19:09 UTC|newest]
Thread overview: 69+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-24 20:54 [dpdk-dev] [PATCH 0/2] librte_net: add crc computation support Jasvinder Singh
2017-02-24 20:54 ` [dpdk-dev] [PATCH 1/2] librte_net: add crc init and compute APIs Jasvinder Singh
2017-02-28 12:08 ` [dpdk-dev] [PATCH v2 0/2] librte_net: add crc computation support Jasvinder Singh
2017-02-28 12:08 ` [dpdk-dev] [PATCH v2 1/2] librte_net: add crc init and compute APIs Jasvinder Singh
2017-02-28 12:15 ` Jerin Jacob
2017-03-01 18:46 ` Thomas Monjalon
2017-03-02 13:03 ` Singh, Jasvinder
2017-03-06 15:27 ` Thomas Monjalon
2017-03-08 11:08 ` De Lara Guarch, Pablo
2017-03-15 17:35 ` Thomas Monjalon
2017-03-15 19:03 ` Dumitrescu, Cristian
2017-03-15 20:15 ` Thomas Monjalon
2017-03-15 21:11 ` Dumitrescu, Cristian
2017-03-15 19:09 ` Dumitrescu, Cristian [this message]
2017-03-12 21:33 ` [dpdk-dev] [PATCH v3 0/2] librte_net: add crc computation support Jasvinder Singh
2017-03-12 21:33 ` [dpdk-dev] [PATCH v3 1/2] librte_net: add crc compute APIs Jasvinder Singh
2017-03-13 3:06 ` Ananyev, Konstantin
2017-03-13 9:05 ` Singh, Jasvinder
2017-03-20 19:29 ` [dpdk-dev] [PATCH v4 0/2] librte_net: add crc computation support Jasvinder Singh
2017-03-20 19:29 ` [dpdk-dev] [PATCH v4 1/2] librte_net: add crc compute APIs Jasvinder Singh
2017-03-21 14:45 ` [dpdk-dev] [PATCH v5 0/2] librte_net: add crc computation support Jasvinder Singh
2017-03-21 14:45 ` [dpdk-dev] [PATCH v5 1/2] librte_net: add crc compute APIs Jasvinder Singh
2017-03-28 18:04 ` De Lara Guarch, Pablo
2017-03-28 18:07 ` De Lara Guarch, Pablo
2017-03-28 19:21 ` Singh, Jasvinder
2017-03-29 12:42 ` [dpdk-dev] [PATCH v6 0/2] librte_net: add crc computation support Jasvinder Singh
2017-03-29 12:42 ` [dpdk-dev] [PATCH v6 1/2] librte_net: add crc compute APIs Jasvinder Singh
2017-03-29 16:14 ` De Lara Guarch, Pablo
2017-03-29 17:15 ` [dpdk-dev] [PATCH v7 0/2] librte_net: add crc computation support Jasvinder Singh
2017-03-29 17:15 ` [dpdk-dev] [PATCH v7 1/2] librte_net: add crc compute APIs Jasvinder Singh
2017-03-30 11:30 ` [dpdk-dev] [PATCH v8 0/2] librte_net: add crc computation support Jasvinder Singh
2017-03-30 11:30 ` [dpdk-dev] [PATCH v8 1/2] librte_net: add crc compute APIs Jasvinder Singh
2017-03-30 11:31 ` Ananyev, Konstantin
2017-03-30 12:06 ` Singh, Jasvinder
2017-03-30 14:40 ` Olivier Matz
2017-03-30 15:14 ` Singh, Jasvinder
2017-03-30 16:15 ` [dpdk-dev] [PATCH v9 0/3] librte_net: add crc computation support Jasvinder Singh
2017-03-30 16:15 ` [dpdk-dev] [PATCH v9 1/3] librte_net: add crc compute APIs Jasvinder Singh
2017-04-04 20:00 ` Thomas Monjalon
2017-04-05 14:58 ` [dpdk-dev] [PATCH v10 0/2] librte_net: add crc computation support Jasvinder Singh
2017-04-05 14:58 ` [dpdk-dev] [PATCH v10 1/2] librte_net: add crc compute APIs Jasvinder Singh
2017-04-05 17:49 ` Thomas Monjalon
2017-04-05 19:22 ` Singh, Jasvinder
2017-04-05 20:49 ` [dpdk-dev] [PATCH v11 0/2] librte_net: add crc computation support Jasvinder Singh
2017-04-05 20:49 ` [dpdk-dev] [PATCH v11 1/2] librte_net: add crc compute APIs Jasvinder Singh
2017-04-05 20:49 ` [dpdk-dev] [PATCH v11 2/2] test/test: add unit test for CRC computation Jasvinder Singh
2017-04-05 20:59 ` Thomas Monjalon
2017-04-05 21:00 ` [dpdk-dev] [PATCH v11 0/2] librte_net: add crc computation support Thomas Monjalon
2017-04-05 14:58 ` [dpdk-dev] [PATCH v10 2/2] test/test: add unit test for CRC computation Jasvinder Singh
2017-03-30 16:15 ` [dpdk-dev] [PATCH v9 2/3] " Jasvinder Singh
2017-03-30 16:15 ` [dpdk-dev] [PATCH v9 3/3] maintainers: add packet crc section and claim maintainership Jasvinder Singh
2017-04-04 19:55 ` Thomas Monjalon
2017-04-04 20:02 ` [dpdk-dev] [PATCH v9 0/3] librte_net: add crc computation support Thomas Monjalon
2017-04-05 8:34 ` Singh, Jasvinder
2017-04-05 9:01 ` Thomas Monjalon
2017-04-05 9:37 ` Richardson, Bruce
2017-04-05 12:52 ` Singh, Jasvinder
2017-03-30 11:30 ` [dpdk-dev] [PATCH v8 2/2] test/test: add unit test for CRC computation Jasvinder Singh
2017-03-29 17:15 ` [dpdk-dev] [PATCH v7 " Jasvinder Singh
2017-03-29 12:42 ` [dpdk-dev] [PATCH v6 " Jasvinder Singh
2017-03-29 16:12 ` De Lara Guarch, Pablo
2017-03-21 14:45 ` [dpdk-dev] [PATCH v5 " Jasvinder Singh
2017-03-28 19:23 ` De Lara Guarch, Pablo
2017-03-28 19:27 ` Singh, Jasvinder
2017-03-20 19:29 ` [dpdk-dev] [PATCH v4 2/2] app/test: " Jasvinder Singh
2017-03-21 7:14 ` Peng, Yuan
2017-03-12 21:33 ` [dpdk-dev] [PATCH v3 " Jasvinder Singh
2017-02-28 12:08 ` [dpdk-dev] [PATCH v2 " Jasvinder Singh
2017-02-24 20:54 ` [dpdk-dev] [PATCH " Jasvinder Singh
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