On Wed, Oct 23, 2019 at 03:16:13AM +0000, Wang, Haiyue wrote:
> > -----Original Message-----
> > From: Ananyev, Konstantin
> > Sent: Wednesday, October 23, 2019 06:52
> > To: Olivier Matz <olivier.m...@6wind.com>; dev@dpdk.org
> > Cc: Andrew Rybchenko <arybche...@solarflare.com>; Richardson, Bruce
> > <bruce.richard...@intel.com>; Wang,
> > Haiyue <haiyue.w...@intel.com>; Jerin Jacob Kollanukkaran
> > <jer...@marvell.com>; Wiles, Keith
> > <keith.wi...@intel.com>; Morten Brørup <m...@smartsharesystems.com>;
> > Stephen Hemminger
> > <step...@networkplumber.org>; Thomas Monjalon <tho...@monjalon.net>
> > Subject: RE: [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.m...@6wind.com>
> > > Acked-by: Thomas Monjalon <tho...@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>
> > > #include <rte_cycles.h>
> > > #include <rte_malloc.h>
> > > +#include <rte_mbuf_dyn.h>
> > >
>
> [snip]
> > > +int
> > > +rte_mbuf_dynflag_register_bitnum(const struct rte_mbuf_dynflag *params,
> > > + unsigned int req)
> > > +{
> > > + int ret;
> > > +
> > > + if (req != UINT_MAX && req >= 64) {
> >
> > Might be better to replace 64 with something like sizeof(mbuf->ol_flags) *
> > CHAR_BIT or so.
>
> Might introduce a new macro like kernel:
>
> /**
> * FIELD_SIZEOF - get the size of a struct's field
> * @t: the target struct
> * @f: the target struct's field
> * Return: the size of @f in the struct definition without having a
> * declared instance of @t.
> */
> #define FIELD_SIZEOF(t, f) (sizeof(((t*)0)->f))
>
> Then: FIELD_SIZEOF(rte_mbuf, ol_flags) * CHAR_BIT
Good idea, thanks
