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From: Yongseok Koh <yskoh@mellanox.com>
To: Andrew Rybchenko <arybchenko@solarflare.com>
Cc: "olivier.matz@6wind.com" <olivier.matz@6wind.com>,
	"david.marchand@redhat.com" <david.marchand@redhat.com>,
	Shahaf Shuler <shahafs@mellanox.com>,
	"dev@dpdk.org" <dev@dpdk.org>,
	"roszenrami@gmail.com" <roszenrami@gmail.com>
Subject: Re: [dpdk-dev] [PATCH v3 1/2] mbuf: add function returning default buffer address
Date: Fri, 11 Jan 2019 11:37:52 +0000
Message-ID: <49ED7E73-6BB0-46DD-AE49-F39B54E18A30@mellanox.com> (raw)
In-Reply-To: <27206464-dcf0-9871-a797-cb0b9f2ff25d@solarflare.com>


> On Jan 11, 2019, at 3:17 AM, Andrew Rybchenko <arybchenko@solarflare.com> wrote:
> 
> 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.

Like the existing rte_mbuf_to_baddr(), it is to return the buf_addr of
the given mbuf. It doesn't matter whether the given mbuf is direct or not.
It should be used at user's discretion.

Yongseok

> 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 
>>>> <yskoh@mellanox.com>
>>>> 
>>>> ---
>>>> 
>>>> 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);
>>>>   }
>>>>   /**
>>>> 
> 

  reply	other threads:[~2019-01-11 11:37 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-09  8:54 [dpdk-dev] [PATCH] net/mlx5: fix instruction hotspot on replenishing Rx buffer Yongseok Koh
2019-01-09  9:38 ` David Marchand
2019-01-09  9:52   ` Olivier Matz
2019-01-09  9:56     ` Yongseok Koh
2019-01-09 10:05       ` David Marchand
2019-01-09 10:11         ` Yongseok Koh
2019-01-09 13:19 ` [dpdk-dev] [PATCH v2 1/2] mbuf: add function returning default buffer address Yongseok Koh
2019-01-09 13:19   ` [dpdk-dev] [PATCH v2 2/2] net/mlx5: fix instruction hotspot on replenishing Rx buffer Yongseok Koh
2019-01-09 13:46   ` [dpdk-dev] [PATCH v2 1/2] mbuf: add function returning default buffer address David Marchand
2019-01-10  1:39     ` Rami Rosen
2019-01-10 18:18       ` Yongseok Koh
2019-01-10 18:22     ` Yongseok Koh
2019-01-10 18:35 ` [dpdk-dev] [PATCH v3 " Yongseok Koh
2019-01-10 18:35   ` [dpdk-dev] [PATCH v3 2/2] net/mlx5: fix instruction hotspot on replenishing Rx buffer Yongseok Koh
2019-01-10 19:10     ` Shahaf Shuler
2019-01-11  8:14   ` [dpdk-dev] [PATCH v3 1/2] mbuf: add function returning default buffer address Andrew Rybchenko
2019-01-11 11:03     ` Yongseok Koh
2019-01-11 11:17       ` Andrew Rybchenko
2019-01-11 11:37         ` Yongseok Koh [this message]
2019-01-11 11:57         ` Bruce Richardson
2019-01-11 12:48           ` David Marchand
2019-01-14 15:51             ` Olivier Matz
2019-01-10 22:40 ` [dpdk-dev] [PATCH v4 " Yongseok Koh
2019-01-10 22:40   ` [dpdk-dev] [PATCH v4 2/2] net/mlx5: fix instruction hotspot on replenishing Rx buffer Yongseok Koh
2019-01-11  8:05   ` [dpdk-dev] [PATCH v4 1/2] mbuf: add function returning default buffer address Olivier Matz
2019-01-11  8:11   ` David Marchand
2019-01-11  8:32     ` David Marchand
2019-01-11 11:09       ` Yongseok Koh
2019-01-11 10:25     ` Thomas Monjalon
2019-01-14 21:16 ` [dpdk-dev] [PATCH v5 1/2] mbuf: add function returning " Yongseok Koh
2019-01-14 21:16   ` [dpdk-dev] [PATCH v5 2/2] net/mlx5: fix instruction hotspot on replenishing Rx buffer Yongseok Koh
2019-02-06 15:54     ` Kevin Traynor
2019-02-21 19:10       ` Kevin Traynor
2019-03-08  2:05         ` Yongseok Koh
2019-01-15  1:35   ` [dpdk-dev] [PATCH v5 1/2] mbuf: add function returning buffer address Thomas Monjalon

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