> -----Original Message-----
> From: Olivier Matz [mailto:olivier.m...@6wind.com]
> Sent: Thursday, September 19, 2019 00:55
> To: dev@dpdk.org
> Cc: Thomas Monjalon <tho...@monjalon.net>; Wang, Haiyue
> <haiyue.w...@intel.com>; Stephen Hemminger
> <step...@networkplumber.org>; Andrew Rybchenko <arybche...@solarflare.com>;
> Wiles, Keith
> <keith.wi...@intel.com>; Jerin Jacob Kollanukkaran <jer...@marvell.com>
> Subject: [PATCH] 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>
> ---
>
> 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 | 114 ++++++-
> 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 | 25 +-
> lib/librte_mbuf/rte_mbuf_dyn.c | 408 +++++++++++++++++++++++++
> lib/librte_mbuf/rte_mbuf_dyn.h | 163 ++++++++++
> lib/librte_mbuf/rte_mbuf_version.map | 4 +
> 8 files changed, 724 insertions(+), 5 deletions(-)
> create mode 100644 lib/librte_mbuf/rte_mbuf_dyn.c
> create mode 100644 lib/librte_mbuf/rte_mbuf_dyn.h
>
[snip]
> +/**
> + * Helper macro to access to a dynamic field.
> + */
> +#define RTE_MBUF_DYNFIELD(m, offset, type) ((type)((uintptr_t)(m) +
> (offset)))
How about to change it as: ?
#define RTE_MBUF_DYNFIELD(m, offset, type) ((type *)((uintptr_t)(m) + (offset)))
^
Then,
*RTE_MBUF_DYNFIELD(mb, xxx, uint32_t) = yyy;
Since we use 'type' like: sizeof(type), __alignof__(type), this makes 'type' be
more consistent, not have to force cast 'type *' when using it.
const struct rte_mbuf_dynfield dynfield2 = {
.name = "test-dynfield2",
.size = sizeof(uint16_t),
.align = __alignof__(uint16_t),
.flags = 0,
};
And also, when I'm trying to use the dynamic flag, found a macro will be better
for making code align with dynamic field. Just a small suggestion. ;-)
mb->ol_flags |= RTE_MBUF_DYNFLAG(ol_offset);
/**
* Helper macro to access to a dynamic flag.
*/
#define RTE_MBUF_DYNFLAG(offset) (1ULL << (offset))
> +
> +#endif
> diff --git a/lib/librte_mbuf/rte_mbuf_version.map
> b/lib/librte_mbuf/rte_mbuf_version.map
> index 2662a37bf..a98310570 100644
> --- a/lib/librte_mbuf/rte_mbuf_version.map
> +++ b/lib/librte_mbuf/rte_mbuf_version.map
> @@ -50,4 +50,8 @@ EXPERIMENTAL {
> global:
>
> rte_mbuf_check;
> + rte_mbuf_dynfield_lookup;
> + rte_mbuf_dynfield_register;
> + rte_mbuf_dynflag_lookup;
> + rte_mbuf_dynflag_register;
> } DPDK_18.08;
> --
> 2.20.1
