[dpdk-dev] [PATCH v2] mbuf: support dynamic fields and flags
Olivier Matz
olivier.matz at 6wind.com
Fri Oct 18 09:53:50 CEST 2019
Hi Haiyue,
On Fri, Oct 18, 2019 at 02:47:50AM +0000, Wang, Haiyue wrote:
> Hi Olivier
>
> > -----Original Message-----
> > From: Olivier Matz [mailto:olivier.matz at 6wind.com]
> > Sent: Thursday, October 17, 2019 22:42
> > To: dev at dpdk.org
> > Cc: Andrew Rybchenko <arybchenko at solarflare.com>; Richardson, Bruce <bruce.richardson at intel.com>; Wang,
> > Haiyue <haiyue.wang at intel.com>; Jerin Jacob Kollanukkaran <jerinj at marvell.com>; Wiles, Keith
> > <keith.wiles at intel.com>; Ananyev, Konstantin <konstantin.ananyev at intel.com>; Morten Brørup
> > <mb at smartsharesystems.com>; Stephen Hemminger <stephen at networkplumber.org>; Thomas Monjalon
> > <thomas at monjalon.net>
> > Subject: [PATCH v2] mbuf: support dynamic fields and flags
> >
> > Many features require to store data inside the mbuf. As the room in mbuf
> > structure is limited, it is not possible to have a field for each
> > feature. Also, changing fields in the mbuf structure can break the API
> > or ABI.
> >
> > This commit addresses these issues, by enabling the dynamic registration
> > of fields or flags:
> >
> > - a dynamic field is a named area in the rte_mbuf structure, with a
> > given size (>= 1 byte) and alignment constraint.
> > - a dynamic flag is a named bit in the rte_mbuf structure.
> >
> > The typical use case is a PMD that registers space for an offload
> > feature, when the application requests to enable this feature. As
> > the space in mbuf is limited, the space should only be reserved if it
> > is going to be used (i.e when the application explicitly asks for it).
> >
> > The registration can be done at any moment, but it is not possible
> > to unregister fields or flags for now.
> >
> > Signed-off-by: Olivier Matz <olivier.matz at 6wind.com>
> > Acked-by: Thomas Monjalon <thomas at monjalon.net>
> > ---
> >
> > v2
> >
> > * Rebase on top of master: solve conflict with Stephen's patchset
> > (packet copy)
> > * Add new apis to register a dynamic field/flag at a specific place
> > * Add a dump function (sugg by David)
> > * Enhance field registration function to select the best offset, keeping
> > large aligned zones as much as possible (sugg by Konstantin)
> > * Use a size_t and unsigned int instead of int when relevant
> > (sugg by Konstantin)
> > * Use "uint64_t dynfield1[2]" in mbuf instead of 2 uint64_t fields
> > (sugg by Konstantin)
> > * Remove unused argument in private function (sugg by Konstantin)
> > * Fix and simplify locking (sugg by Konstantin)
> > * Fix minor typo
> >
> > rfc -> v1
> >
> > * Rebase on top of master
> > * Change registration API to use a structure instead of
> > variables, getting rid of #defines (Stephen's comment)
> > * Update flag registration to use a similar API as fields.
> > * Change max name length from 32 to 64 (sugg. by Thomas)
> > * Enhance API documentation (Haiyue's and Andrew's comments)
> > * Add a debug log at registration
> > * Add some words in release note
> > * Did some performance tests (sugg. by Andrew):
> > On my platform, reading a dynamic field takes ~3 cycles more
> > than a static field, and ~2 cycles more for writing.
> >
> > app/test/test_mbuf.c | 145 ++++++-
> > doc/guides/rel_notes/release_19_11.rst | 7 +
> > lib/librte_mbuf/Makefile | 2 +
> > lib/librte_mbuf/meson.build | 6 +-
> > lib/librte_mbuf/rte_mbuf.h | 23 +-
> > lib/librte_mbuf/rte_mbuf_dyn.c | 548 +++++++++++++++++++++++++
> > lib/librte_mbuf/rte_mbuf_dyn.h | 226 ++++++++++
> > lib/librte_mbuf/rte_mbuf_version.map | 7 +
> > 8 files changed, 959 insertions(+), 5 deletions(-)
> > create mode 100644 lib/librte_mbuf/rte_mbuf_dyn.c
> > create mode 100644 lib/librte_mbuf/rte_mbuf_dyn.h
> >
> > diff --git a/app/test/test_mbuf.c b/app/test/test_mbuf.c
> > index b9c2b2500..01cafad59 100644
> > --- a/app/test/test_mbuf.c
> > +++ b/app/test/test_mbuf.c
> > @@ -28,6 +28,7 @@
> > #include <rte_random.h>
>
> [snip]
>
> > +/**
> > + * Helper macro to access to a dynamic field.
> > + */
> > +#define RTE_MBUF_DYNFIELD(m, offset, type) ((type)((uintptr_t)(m) + (offset)))
> > +
>
> The suggested macro is missed ? ;-)
> /**
> * Helper macro to access to a dynamic flag.
> */
> #define RTE_MBUF_DYNFLAG(offset) (1ULL << (offset))
Yes, sorry.
Thinking a bit more about it, I wonder if the macros below aren't
more consistent with the dynamic field (because they take the mbuf
as parameter)?
#define RTE_MBUF_SET_DYNFLAG(m, bitnum, val) ...
#define RTE_MBUF_GET_DYNFLAG(m, bitnum) ...
They could even be static inline functions.
On the other hand, these helpers would be generic to ol_flags, not only
for dynamic flags. Today, we use (1ULL << bit) for ol_flags, which makes
me wonder... is the macro really needed after all? :)
> BTW, should we have a place to put the registered dynamic fields and flags
> names together (a name overview -- detail Link to --> PMD's help page) ?
The centralized place will be in rte_mbuf_dyn.h for fields/flags that can
are shared between several dpdk areas. Some libraries/pmd could have private
dynamic fields/flags. In any case, I think the same namespace than functions
should be used. Probably something like this:
- "rte_mbuf_dynfield_<name>" in mbuf lib
- "rte_<libname>_dynfield_<name>" in other libs
- "rte_net_<pmd>_dynfield_<name>" in pmds
- "<name>" in apps
> Since rte_mbuf_dynfield:name & rte_mbuf_dynflag:name work as a API style,
> users can check how many 'names' registered, developers can check whether
> the names they want to use are registered or not ? They don't need to have
> to check the rte_errno ... Just a suggestion for user experience.
I did not get you point. Does my response above answers to your question?
Regards,
Olivier
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