From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Rybchenko Subject: Re: [PATCH v3 1/2] mbuf: add function returning default buffer address Date: Fri, 11 Jan 2019 14:17:04 +0300 Message-ID: <27206464-dcf0-9871-a797-cb0b9f2ff25d@solarflare.com> References: <20190109085426.39965-1-yskoh@mellanox.com> <20190110183528.42503-1-yskoh@mellanox.com> <2934bc73-98e6-643a-0d61-cf7804e1535d@solarflare.com> <20190111110332.GA8355@minint-98vp2qg> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit Cc: Shahaf Shuler , "dev@dpdk.org" , "roszenrami@gmail.com" To: Yongseok Koh , "olivier.matz@6wind.com" , "david.marchand@redhat.com" Return-path: Received: from dispatch1-us1.ppe-hosted.com (dispatch1-us1.ppe-hosted.com [67.231.154.164]) by dpdk.org (Postfix) with ESMTP id 717E41B938 for ; Fri, 11 Jan 2019 12:17:16 +0100 (CET) In-Reply-To: <20190111110332.GA8355@minint-98vp2qg> Content-Language: en-GB List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" Olivier, David, could you take a look at naming suggested below and share your thoughts. My fear is that rte_mbuf_buf_addr() is too generic and true for direct mbuf only. That's why I'd like to highlight it in the function name. Thanks, Andrew. On 1/11/19 2:03 PM, Yongseok Koh wrote: > On Fri, Jan 11, 2019 at 11:14:22AM +0300, Andrew Rybchenko wrote: >> On 1/10/19 9:35 PM, Yongseok Koh wrote: >>> This patch introduces two new functions - rte_mbuf_buf_addr() and >>> rte_mbuf_data_addr_default(). >>> >>> rte_mbuf_buf_addr() reutrns the default buffer address of given mbuf which >>> comes after mbuf structure and private data. >>> >>> rte_mbuf_data_addr_default() returns the default address of mbuf data >>> taking the headroom into account. >>> >>> Signed-off-by: Yongseok Koh >>> --- >>> >>> v3: >>> * rename functions >>> >>> v2: >>> * initial implementation >>> >>> lib/librte_mbuf/rte_mbuf.h | 43 ++++++++++++++++++++++++++++++++++++++++--- >>> 1 file changed, 40 insertions(+), 3 deletions(-) >>> >>> diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h >>> index bc562dc8a9..486566fc28 100644 >>> --- a/lib/librte_mbuf/rte_mbuf.h >>> +++ b/lib/librte_mbuf/rte_mbuf.h >>> @@ -788,8 +788,47 @@ rte_mbuf_from_indirect(struct rte_mbuf *mi) >>> } >>> /** >>> + * Return the default buffer address of the mbuf. >>> + * >>> + * @param mb >>> + * The pointer to the mbuf. >>> + * @param mp >>> + * The pointer to the mempool of the mbuf. >>> + * @return >>> + * The pointer of the mbuf buffer. >>> + */ >>> +static inline char * __rte_experimental >>> +rte_mbuf_buf_addr(struct rte_mbuf *mb, struct rte_mempool *mp) >> struct rte_mbuf has pool member. So, I don't understand why mp >> argument is required. I guess there is a reason, but it should be >> explained in comments. I see motivation in rte_mbuf_to_baddr() >> description, but rte_mbuf_buf_add() does not explain it. > Well, I don't like to put same comment here and there but I'll add small comment > here. > >> Also right now the function name looks like simple get accessor for >> buf_addr and I'd expect to seem one line implementation may be >> with extra debug checks: return mb->buf_addr. > This func is suggested by David and Olivier because same code is being repeated > in multiple locations. This can be used to initialize a mbuf when mb->buf_addr is > null. And second use-case (this is my use-case) is to get the buf_addr without > accessing the mbuf struct when mempool of mbuf is known, e.g. Rx buffer > replenishment. It is definitely beneficial for performance, especially RISC > cores. > >> May be rte_mbuf_direct_buf_addr() ? >> If so, similar below rte_mbuf_direct_data_addr_default(). > Regarding naming, people have different tastes. As it is acked by Olivier and > David, I'll keep the names. > Thanks, > Yongseok > >>> +{ >>> + char *buffer_addr; >>> + >>> + buffer_addr = (char *)mb + sizeof(*mb) + rte_pktmbuf_priv_size(mp); >>> + return buffer_addr; >>> +} >>> + >>> + >>> +/** >>> + * Return the default address of the beginning of the mbuf data. >>> + * >>> + * @param mb >>> + * The pointer to the mbuf. >>> + * @return >>> + * The pointer of the beginning of the mbuf data. >>> + */ >>> +static inline char * __rte_experimental >>> +rte_mbuf_data_addr_default(struct rte_mbuf *mb) >>> +{ >>> + return rte_mbuf_buf_addr(mb, mb->pool) + RTE_PKTMBUF_HEADROOM; >>> +} >>> + >>> +/** >>> * Return the buffer address embedded in the given mbuf. >>> * >>> + * Note that accessing mempool pointer of a mbuf is expensive because the >>> + * pointer is stored in the 2nd cache line of mbuf. If mempool is known, it >>> + * is better not to reference the mempool pointer in mbuf but calling >>> + * rte_mbuf_buf_addr() would be more efficient. >>> + * >>> * @param md >>> * The pointer to the mbuf. >>> * @return >>> @@ -798,9 +837,7 @@ rte_mbuf_from_indirect(struct rte_mbuf *mi) >>> static inline char * >>> rte_mbuf_to_baddr(struct rte_mbuf *md) >>> { >>> - char *buffer_addr; >>> - buffer_addr = (char *)md + sizeof(*md) + rte_pktmbuf_priv_size(md->pool); >>> - return buffer_addr; >>> + return rte_mbuf_buf_addr(md, md->pool); >>> } >>> /**