From: Thomas Monjalon <thomas@monjalon.net>
To: "Morten Brørup" <mb@smartsharesystems.com>,
"Stephen Hemminger" <stephen@networkplumber.org>,
"Wiles, Keith" <keith.wiles@intel.com>,
"Olivier Matz" <olivier.matz@6wind.com>
Cc: "Yang, Zhiyong" <zhiyong.yang@intel.com>,
dev@dpdk.org, "Wang, Zhihong" <zhihong.wang@intel.com>,
"Yuanhan Liu" <yuanhan.liu@linux.intel.com>,
"Ananyev, Konstantin" <konstantin.ananyev@intel.com>,
"Richardson, Bruce" <bruce.richardson@intel.com>,
"Chilikin, Andrey" <andrey.chilikin@intel.com>,
"Jan Blunck" <jblunck@infradead.org>,
"Nélio Laranjeiro" <nelio.laranjeiro@6wind.com>,
arybchenko@solarflare.com, jerin.jacob@caviumnetworks.com
Subject: Re: [dpdk-dev] [PATCH v2 6/8] mbuf: use 2 bytes for port andnbsegments
Date: Wed, 12 Jul 2017 18:23:38 +0200 [thread overview]
Message-ID: <1911402.Nq572ABAkn@xps> (raw)
In-Reply-To: <98CBD80474FA8B44BF855DF32C47DC359EB297@smartserver.smartshare.dk>
12/07/2017 17:57, Morten Brørup:
> From: Stephen Hemminger
> > Morten Brørup <mb@smartsharesystems.com> wrote:
> > > From: Yang, Zhiyong [mailto:zhiyong.yang@intel.com]
> > > > From: Morten Brørup
> > > > > From: Wiles, Keith
> > > > > > > On Jul 11, 2017, at 10:23 AM, Morten Brørup wrote:
> > > > > > > From: Thomas Monjalon
> > > > > > >> 11/07/2017 15:30, Morten Brørup:
> > > > > > >>> Morten Brørup wrote:
> > > > > > >>>> Olivier Matz wrote:
> > > > > > >>>>> As I said in a previous message, I think a good first
> > > > > > >>>>> step would be to introduce a typedef for the port
> > > > > > >>>>> number: rte_eth_port_num_t.
> > > > > > >>>>> It can still be uint8_t for now, and can be switched
> > > > > > >>>>> to 16 bits in one step when everyone uses this new type.
> > > > > > >>>>
> > > > > > >>>> I think that DPDK follows the Linux tradition of exposing
> > > > > > >>>> the variable types, as opposed to hiding them behind
> > > > > > >>>> typedefs. This has the unfortunate consequence that
> > > > > > >>>> when a variable type changes, it has to be changed everywhere.
> > > > > > >>>>
> > > > > > >>>> Introducing a rte_eth_port_num_t will require changing the
> > > > > > >>>> same files at the same locations everywhere, so not even as a
> > > > > > >>>> temporary solution will it be beneficial.
> > > > > > >> [...]
> > > > > > >>> What I was trying to communicate with my long argument
> > > > > > >>> about type definitions was:
> > > > > > >>> When the type changed from 8 bit to 16 bit, the type
> > > > > > >>> needs to change from uint8_t to uint16_t everywhere too,
> > > > > > >>> including in the ethdev APIs.
> > > > > > >>>
> > > > > > >>> Don't start breaking coding conventions here by hiding the
> > > > > > >>> type of this variable.
> > > > > > >>
> > > > > > >> So, Morten, you are against the typedef, right?
> > > > > > >> Because we need to change it everywhere anyway, right?
> > > > > > >>
> > > > > > >> Note: I have no strong opinion.
> > > > > > >
> > > > > > > I'm against the typedef because it would break convention,
> > > > > > > and I'm a strong proponent of conventions.
> > > > > > > In other projects, I'm all for typedefs, virtual classes,
> > > > > > > inheritance etc., but DPDK follows the Linux convention
> > > > > > > of not hiding simple types.
> > > > > > >
> > > > > > > We need to change it from uint8_t everywhere, regardless what
> > > > > > > we change it to. (But if we need to change it again sometime
> > > > > > > in the future, then a typedef will save us next time.)
> > > > > >
> > > > > > If the number of ports go beyond 64K then I will be the first
> > > > > > one (if still alive) to eat this email. :-) The only reason to
> > > > > > have more then 2 bytes would be to encode something into the
> > > > > > port id value, which I could see, but a very slim chance IMHO.
> > > > > >
> > > > > > > My preference: Follow convention and change it to uint16_t
> > > > > > > everywhere.
> > > > > >
> > > > > > As we must change the uint8_t to uint16_t, then I would like it
> > > > > > to be more descriptive via a typedef. I really do not see us
> > > > > > needing to change it again in the near future.
> > > > > > The only reason to make it a typedef is to be able to identify
> > > > > > from just the prototype of the function that it takes a port
> > > > > > ID value, which I am in favor of doing here for that reason.
> > > > >
> > > > > That is not a very good reason: When used as a function
> > > > > parameter, the type is only shown in the function declaration,
> > > > > whereas the variable name is shown every time it is used inside
> > > > > the function.
> > > > > So remember to always use meaningful variable names, such as
> > > > > "port" (like in the mbuf structure) or "port_id" (used in other
> > > > > places).
> > > > >
> > > > > I still don't support typedefs for scalar types. I consider it
> > > > > against the coding style, although after reviewing the official
> > > > > DPDK Coding Style documentation
> > > > > (http://dpdk.org/doc/guides/contributing/coding_style.html),
> > > > > I can see that it is not explicitly stated. Please also note
> > > > > that section 1.5.7 of the DPDK Coding Style documentation says
> > > > > that the _t postfix should be avoided. Anyway, if we end up
> > > > > with a typedef, please don't use something resembling pid_t
> > > > > known from POSIX
> > > > > (https://www.gnu.org/software/libc/manual/html_node/Process-
> > > > > Identification.html).
> > > >
> > > > How about rte_dev_id_t?
> > >
> > > If the DPDK Coding Style is based on Linux Coding Style, we should
> > > avoid typedefs in general, not just for structures. Please read Linus
> > > Torvalds' opinions about it:
> > > http://yarchive.net/comp/linux/typedefs.html
> > >
> > > Perhaps the DPDK Coding Style should be updated to clarify this. (Or
> > > if we decide otherwise, to explicitly mention this deviation from the
> > > Linux coding style.)
> >
> > It is logical to use typedef's for this kind of scalar type that may
> > need to change.
> > Names matter, please avoid pid (confuse with posix) and dev (confuse
> > with device id).
> > I would prefer: rte_portid_t and rte_queueid_t
> >
> > Longer term, probably rte_eth_devices[] needs to go. Change port id
> > into something more like ifindex. And use sparse data structure to
> > allow very large number of devices and non-contiguous lookup. Think of
> > a VPN server where each VPN connection looks like a DPDK device.
>
> We are using a non-contiguous ifindex in our firmware, for virtual
> interfaces as you mention, so I get your point here!
> But until DPDK gets there, I suppose the DPDK port id is considered
> more or less contiguous.
>
> You clearly have a longer track record working with Linus than me,
> so if you interpret the coding style like that, I will not object
> anymore - as my objection was based on coding style. And will someone
> please update the DPDK Coding Style document accordingly...
>
> rte_portid_t is fine with me, but why not just rte_port_t?
One problem with opaque typedef is that we don't know how to print them,
except if we have a PRIx macro.
So I suggest to keep with uint16_t (my preference),
or to add a printf format macro.
next prev parent reply other threads:[~2017-07-12 16:23 UTC|newest]
Thread overview: 155+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-24 15:19 [dpdk-dev] [RFC 0/8] mbuf: structure reorganization Olivier Matz
2017-01-24 15:19 ` [dpdk-dev] [RFC 1/8] mbuf: make segment prefree function public Olivier Matz
2017-01-24 15:19 ` [dpdk-dev] [RFC 2/8] mbuf: make raw free " Olivier Matz
2017-01-24 15:19 ` [dpdk-dev] [RFC 3/8] mbuf: set mbuf fields while in pool Olivier Matz
2017-01-24 15:50 ` Bruce Richardson
2017-02-28 14:51 ` Olivier Matz
2017-01-24 15:19 ` [dpdk-dev] [RFC 4/8] net: don't touch mbuf next or nb segs on Rx Olivier Matz
2017-01-24 15:19 ` [dpdk-dev] [RFC 5/8] mbuf: make rearm data address naturally aligned Olivier Matz
2017-01-24 15:19 ` [dpdk-dev] [RFC 6/8] mbuf: use 2 bytes for port and nb segments Olivier Matz
2017-01-24 15:19 ` [dpdk-dev] [RFC 7/8] mbuf: move sequence number in second cache line Olivier Matz
2017-01-24 15:19 ` [dpdk-dev] [RFC 8/8] mbuf: add a timestamp field Olivier Matz
2017-01-24 15:59 ` [dpdk-dev] [RFC 0/8] mbuf: structure reorganization Bruce Richardson
2017-01-24 16:16 ` Olivier MATZ
2017-02-06 18:41 ` Ananyev, Konstantin
2017-02-09 16:20 ` Morten Brørup
2017-02-09 16:56 ` Ananyev, Konstantin
2017-02-16 13:48 ` Olivier Matz
2017-02-16 15:46 ` Bruce Richardson
2017-02-16 16:14 ` Olivier Matz
2017-02-21 14:20 ` Morten Brørup
2017-02-21 14:28 ` Bruce Richardson
2017-02-21 15:04 ` Olivier MATZ
2017-02-21 15:18 ` Bruce Richardson
2017-02-21 15:18 ` Morten Brørup
2017-02-19 19:04 ` Chilikin, Andrey
2017-02-21 9:53 ` Olivier MATZ
2017-02-16 17:26 ` Jan Blunck
2017-02-17 10:51 ` Olivier Matz
2017-02-17 12:49 ` Nélio Laranjeiro
2017-02-17 13:51 ` Jan Blunck
2017-02-18 5:48 ` Andrew Rybchenko
2017-02-17 13:38 ` Jan Blunck
2017-02-17 14:17 ` Olivier Matz
2017-02-17 18:42 ` Ananyev, Konstantin
2017-02-21 9:53 ` Olivier MATZ
2017-02-21 10:28 ` Ananyev, Konstantin
2017-02-20 9:27 ` Jan Blunck
2017-02-21 9:54 ` Olivier MATZ
2017-02-21 16:12 ` Jan Blunck
2017-02-21 16:38 ` Bruce Richardson
2017-02-21 17:04 ` Jan Blunck
2017-02-21 17:26 ` Ananyev, Konstantin
2017-02-21 19:17 ` Jan Blunck
2017-02-21 20:30 ` Ananyev, Konstantin
2017-02-21 21:51 ` Morten Brørup
2017-02-24 14:11 ` Olivier Matz
2017-02-24 14:00 ` Olivier Matz
2017-02-24 14:21 ` Bruce Richardson
2017-02-28 8:55 ` Jan Blunck
2017-02-28 9:05 ` Ananyev, Konstantin
2017-02-28 9:23 ` Olivier Matz
2017-02-28 9:33 ` Jan Blunck
2017-02-28 10:29 ` Ananyev, Konstantin
2017-02-28 10:50 ` Olivier Matz
2017-02-28 11:48 ` Ananyev, Konstantin
2017-02-28 12:28 ` Olivier Matz
2017-02-28 22:53 ` Ananyev, Konstantin
2017-03-02 16:46 ` Olivier Matz
2017-03-08 11:11 ` Ananyev, Konstantin
2017-03-20 9:00 ` Olivier Matz
2017-03-22 17:42 ` Ananyev, Konstantin
2017-03-24 8:35 ` Jerin Jacob
2017-03-24 13:35 ` Olivier Matz
2017-02-28 9:25 ` Jan Blunck
2017-02-19 23:45 ` Ananyev, Konstantin
2017-02-21 9:22 ` Morten Brørup
2017-02-21 9:54 ` Olivier MATZ
2017-03-08 9:41 ` [dpdk-dev] [PATCH 0/9] " Olivier Matz
2017-03-08 9:41 ` [dpdk-dev] [PATCH 1/9] mbuf: make segment prefree function public Olivier Matz
2017-03-08 9:41 ` [dpdk-dev] [PATCH 2/9] mbuf: make raw free " Olivier Matz
2017-03-08 9:41 ` [dpdk-dev] [PATCH 3/9] mbuf: set mbuf fields while in pool Olivier Matz
2017-03-31 11:21 ` Bruce Richardson
2017-03-31 11:51 ` Ananyev, Konstantin
2017-03-08 9:41 ` [dpdk-dev] [PATCH 4/9] drivers/net: don't touch mbuf next or nb segs on Rx Olivier Matz
2017-03-08 9:41 ` [dpdk-dev] [PATCH 5/9] mbuf: make rearm data address naturally aligned Olivier Matz
2017-03-08 9:41 ` [dpdk-dev] [PATCH 6/9] mbuf: use 2 bytes for port and nb segments Olivier Matz
2017-03-08 9:41 ` [dpdk-dev] [PATCH 7/9] mbuf: move sequence number in second cache line Olivier Matz
2017-03-08 9:42 ` [dpdk-dev] [PATCH 8/9] mbuf: add a timestamp field Olivier Matz
2017-04-04 10:29 ` [dpdk-dev] [PATCH 0/2] reduce writes to mbuf in ixgbe vRX Konstantin Ananyev
2017-04-07 15:13 ` Ferruh Yigit
2017-04-07 15:44 ` Ferruh Yigit
2017-04-09 22:56 ` Ananyev, Konstantin
2017-04-04 10:29 ` [dpdk-dev] [PATCH 1/2] net/ixgbe: eliminate mbuf write on rearm Konstantin Ananyev
2017-04-10 15:59 ` [dpdk-dev] [PATCH v2 0/2] reduce writes to mbuf in ixgbe vRX Konstantin Ananyev
2017-04-10 16:17 ` Ferruh Yigit
2017-04-10 15:59 ` [dpdk-dev] [PATCH v2 1/2] net/ixgbe: eliminate mbuf write on rearm Konstantin Ananyev
2017-04-10 15:59 ` [dpdk-dev] [PATCH v2 2/2] net/ixgbe: remove option to disable offload flags Konstantin Ananyev
2017-04-04 10:29 ` [dpdk-dev] [PATCH " Konstantin Ananyev
2017-03-08 9:42 ` [dpdk-dev] [PATCH 9/9] mbuf: reorder VLAN tci and buffer len fields Olivier Matz
2017-03-29 15:56 ` [dpdk-dev] [PATCH 0/9] mbuf: structure reorganization Olivier Matz
2017-03-29 16:03 ` Morten Brørup
2017-03-29 20:09 ` Bruce Richardson
2017-03-30 9:31 ` Bruce Richardson
2017-03-30 12:02 ` Olivier Matz
2017-03-30 12:23 ` Bruce Richardson
2017-03-30 16:45 ` Ananyev, Konstantin
2017-03-30 16:47 ` Ananyev, Konstantin
2017-03-30 18:06 ` Ananyev, Konstantin
2017-03-31 8:41 ` Olivier Matz
2017-03-31 9:58 ` Ananyev, Konstantin
2017-03-31 1:00 ` Ananyev, Konstantin
2017-03-31 7:21 ` Morten Brørup
2017-03-31 8:26 ` Olivier Matz
2017-03-31 8:41 ` Bruce Richardson
2017-03-31 8:59 ` Olivier Matz
2017-03-31 9:18 ` Ananyev, Konstantin
2017-03-31 9:36 ` Olivier Matz
2017-04-03 16:15 ` Thomas Monjalon
2017-04-04 7:58 ` Olivier MATZ
2017-04-04 8:53 ` Bruce Richardson
2017-03-31 9:23 ` Bruce Richardson
2017-03-31 11:18 ` Nélio Laranjeiro
2017-03-30 14:54 ` Andrew Rybchenko
2017-03-30 15:12 ` Jerin Jacob
2017-04-04 16:27 ` [dpdk-dev] [PATCH v2 0/8] " Olivier Matz
2017-04-04 16:28 ` [dpdk-dev] [PATCH v2 1/8] mbuf: make segment prefree function public Olivier Matz
2017-04-04 16:28 ` [dpdk-dev] [PATCH v2 2/8] mbuf: make raw free " Olivier Matz
2017-04-04 16:28 ` [dpdk-dev] [PATCH v2 3/8] mbuf: set mbuf fields while in pool Olivier Matz
2017-04-04 16:28 ` [dpdk-dev] [PATCH v2 4/8] drivers/net: don't touch mbuf next or nb segs on Rx Olivier Matz
2017-04-04 16:28 ` [dpdk-dev] [PATCH v2 5/8] mbuf: make rearm data address naturally aligned Olivier Matz
2017-04-04 16:28 ` [dpdk-dev] [PATCH v2 6/8] mbuf: use 2 bytes for port and nb segments Olivier Matz
2017-04-06 5:45 ` Yuanhan Liu
2017-04-18 13:03 ` Olivier MATZ
2017-07-04 7:54 ` Wang, Zhihong
2017-07-10 8:00 ` Olivier Matz
2017-07-10 8:15 ` Morten Brørup
2017-07-11 13:25 ` Wiles, Keith
2017-07-11 13:30 ` Morten Brørup
2017-07-11 15:05 ` Thomas Monjalon
2017-07-11 15:23 ` [dpdk-dev] [PATCH v2 6/8] mbuf: use 2 bytes for port and nbsegments Morten Brørup
2017-07-11 16:48 ` Wiles, Keith
2017-07-12 7:25 ` Morten Brørup
2017-07-12 9:02 ` Yang, Zhiyong
2017-07-12 9:50 ` [dpdk-dev] [PATCH v2 6/8] mbuf: use 2 bytes for port andnbsegments Morten Brørup
2017-07-12 15:35 ` Stephen Hemminger
2017-07-12 15:57 ` Morten Brørup
2017-07-12 16:23 ` Thomas Monjalon [this message]
2017-07-12 18:20 ` Wiles, Keith
2017-07-21 15:03 ` Bruce Richardson
2017-07-12 15:34 ` [dpdk-dev] [PATCH v2 6/8] mbuf: use 2 bytes for port and nbsegments Wiles, Keith
2017-07-11 13:34 ` [dpdk-dev] [PATCH v2 6/8] mbuf: use 2 bytes for port and nb segments Wiles, Keith
2017-07-11 13:46 ` Olivier MATZ
2017-04-04 16:28 ` [dpdk-dev] [PATCH v2 7/8] mbuf: move sequence number in second cache line Olivier Matz
2017-04-04 16:28 ` [dpdk-dev] [PATCH v2 8/8] mbuf: add a timestamp field Olivier Matz
2017-04-05 9:37 ` [dpdk-dev] [PATCH v2 0/8] mbuf: structure reorganization Thomas Monjalon
2017-04-05 9:46 ` Olivier MATZ
2017-04-05 9:48 ` Richardson, Bruce
2017-04-05 12:06 ` Ferruh Yigit
2017-04-14 13:10 ` Ferruh Yigit
2017-04-18 13:04 ` Olivier MATZ
2017-04-19 9:39 ` Thomas Monjalon
2017-04-19 12:28 ` Olivier MATZ
2017-04-19 12:56 ` Thomas Monjalon
2017-04-19 13:03 ` Ferruh Yigit
2017-04-19 13:12 ` Thomas Monjalon
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