> -----Original Message----- > From: Olivier Matz [mailto:olivier.m...@6wind.com] > Sent: Friday, October 18, 2019 17:48 > To: Wang, Haiyue <haiyue.w...@intel.com> > Cc: dev@dpdk.org; Andrew Rybchenko <arybche...@solarflare.com>; Richardson, > Bruce > <bruce.richard...@intel.com>; Jerin Jacob Kollanukkaran <jer...@marvell.com>; > Wiles, Keith > <keith.wi...@intel.com>; Ananyev, Konstantin <konstantin.anan...@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 > > On Fri, Oct 18, 2019 at 08:28:02AM +0000, Wang, Haiyue wrote: > > Hi Olivier, > > > > > -----Original Message----- > > > From: Olivier Matz [mailto:olivier.m...@6wind.com] > > > Sent: Friday, October 18, 2019 15:54 > > > To: Wang, Haiyue <haiyue.w...@intel.com> > > > Cc: dev@dpdk.org; Andrew Rybchenko <arybche...@solarflare.com>; > > > Richardson, Bruce > > > <bruce.richard...@intel.com>; Jerin Jacob Kollanukkaran > > > <jer...@marvell.com>; Wiles, Keith > > > <keith.wi...@intel.com>; Ananyev, Konstantin > > > <konstantin.anan...@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 > > > > > > Hi Haiyue, > > > > > > On Fri, Oct 18, 2019 at 02:47:50AM +0000, Wang, Haiyue wrote: > > > > Hi Olivier > > > > > > > > > -----Original Message----- > > > > > From: Olivier Matz [mailto:olivier.m...@6wind.com] > > > > > Sent: Thursday, October 17, 2019 22:42 > > > > > To: 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>; Ananyev, Konstantin > > > > > <konstantin.anan...@intel.com>; Morten Brørup > > > > > <m...@smartsharesystems.com>; Stephen Hemminger > > > > > <step...@networkplumber.org>; Thomas Monjalon > > > > > <tho...@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.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> > > > > > > > > [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? :) > > > > > > > I used as this: > > 1). in PMD: > > mb->ol_flags |= RTE_MBUF_DYNFLAG(ol_offset); > > > > > > 2). In testpmd > > if (mb->ol_flags & RTE_MBUF_DYNFLAG(ol_offset)) > > ... > > > > The above two macros look better in real use. > > I just looked at http://patchwork.dpdk.org/patch/60908/ > In the patch, a mask is used instead of a bit number, which is indeed > better in terms of performance. This makes the macro not that useful, > given there is a specific helper. >
'a mask is used instead of a bit number' good practice, yes, then no need this macro, thanks for sharing. ;-)
