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[2a01:cb0c:5:a600:226:b0ff:feed:2fc]) by smtp.gmail.com with ESMTPSA id r13sm6216959wra.74.2019.10.18.02.47.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 18 Oct 2019 02:47:49 -0700 (PDT) Date: Fri, 18 Oct 2019 11:47:48 +0200 From: Olivier Matz To: "Wang, Haiyue" Cc: "dev@dpdk.org" , Andrew Rybchenko , "Richardson, Bruce" , Jerin Jacob Kollanukkaran , "Wiles, Keith" , "Ananyev, Konstantin" , Morten =?utf-8?Q?Br=C3=B8rup?= , Stephen Hemminger , Thomas Monjalon Message-ID: <20191018094748.3r7dbzqvbb3rsv7u@platinum> References: <20190710092907.5565-1-olivier.matz@6wind.com> <20191017144219.32708-1-olivier.matz@6wind.com> <20191018075350.bxrcsxhsgu2uaph7@platinum> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: NeoMutt/20180716 Subject: Re: [dpdk-dev] [PATCH v2] mbuf: support dynamic fields and flags X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On Fri, Oct 18, 2019 at 08:28:02AM +0000, Wang, Haiyue wrote: > Hi Olivier, > > > -----Original Message----- > > From: Olivier Matz [mailto:olivier.matz@6wind.com] > > Sent: Friday, October 18, 2019 15:54 > > To: Wang, Haiyue > > Cc: dev@dpdk.org; Andrew Rybchenko ; Richardson, Bruce > > ; Jerin Jacob Kollanukkaran ; Wiles, Keith > > ; Ananyev, Konstantin ; Morten Brørup > > ; Stephen Hemminger ; Thomas Monjalon > > > > 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.matz@6wind.com] > > > > Sent: Thursday, October 17, 2019 22:42 > > > > To: dev@dpdk.org > > > > Cc: Andrew Rybchenko ; Richardson, Bruce ; > > Wang, > > > > Haiyue ; Jerin Jacob Kollanukkaran ; Wiles, Keith > > > > ; Ananyev, Konstantin ; Morten Brørup > > > > ; Stephen Hemminger ; Thomas Monjalon > > > > > > > > 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 > > > > Acked-by: Thomas Monjalon > > > > --- > > > > > > > > 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 > > > > > > [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. > > > 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_" in mbuf lib > > - "rte__dynfield_" in other libs > > - "rte_net__dynfield_" in pmds > > - "" 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? > > > > Yes, the name conversation you mentioned above is a good practice, then no doc > needed any more, thanks! > > > Regards, > > Olivier