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From: Olivier MATZ <olivier.matz@6wind.com>
To: Bruce Richardson <bruce.richardson@intel.com>, dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH 01/13] mbuf: replace data pointer by an offset
Date: Mon, 08 Sep 2014 11:52:31 +0200
Message-ID: <540D7C5F.8000406@6wind.com> (raw)
In-Reply-To: <1409759378-10113-2-git-send-email-bruce.richardson@intel.com>

Hi Bruce,

On 09/03/2014 05:49 PM, Bruce Richardson wrote:
> From: Olivier Matz <olivier.matz@6wind.com>
> 
> Original patch:
>  The mbuf structure already contains a pointer to the beginning of the
>  buffer (m->buf_addr). It is not needed to use 8 bytes again to store
>  another pointer to the beginning of the data.
> 
>  Using a 16 bits unsigned integer is enough as we know that a mbuf is
>  never longer than 64KB. We gain 6 bytes in the structure thanks to
>  this modification.
> 
>  Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
> 
> This version:
> * Updated original patch to apply to latest on mainline.
> * Disabled vector PMD in config as it relies heavily on the mbuf layout
>   This will be re-enabled in a subsequent commit once vPMD has been
>   reworked to take account of mbuf changes.
> 
> Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
>
> [...]
>
> diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h
> index 32e8474..669e7f5 100644
> --- a/lib/librte_mbuf/rte_mbuf.h
> +++ b/lib/librte_mbuf/rte_mbuf.h
> @@ -119,6 +119,13 @@ struct rte_mbuf {
>  	void *buf_addr;           /**< Virtual address of segment buffer. */
>  	phys_addr_t buf_physaddr; /**< Physical address of segment buffer. */
>  	uint16_t buf_len;         /**< Length of segment buffer. */
> +
> +	/* valid for any segment */
> +	struct rte_mbuf *next;    /**< Next segment of scattered packet. */
> +	uint16_t data_off;
> +	uint16_t data_len;        /**< Amount of data in segment buffer. */
> +	uint32_t pkt_len;         /**< Total pkt len: sum of all segments. */
> +

Here, the compiler will add some padding between "buf_len" and "next"
(6 bytes in 64bits, 2 in 32bits). Shouldn't we add "reserved" fields
or at least a comment ? Another idea would be to reorganize the fields
to avoid padding, if possible.

Except this remarq, Acked-by: Olivier Matz <olivier.matz@6wind.com>

  reply	other threads:[~2014-09-08  9:47 UTC|newest]

Thread overview: 62+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-09-03 15:49 [dpdk-dev] [PATCH 00/13] Mbuf Structure Rework, part 2 Bruce Richardson
2014-09-03 15:49 ` [dpdk-dev] [PATCH 01/13] mbuf: replace data pointer by an offset Bruce Richardson
2014-09-08  9:52   ` Olivier MATZ [this message]
2014-09-08  9:55     ` Olivier MATZ
2014-09-03 15:49 ` [dpdk-dev] [PATCH 02/13] mbuf: reorder fields by time of use Bruce Richardson
2014-09-08 10:17   ` Olivier MATZ
2014-09-03 15:49 ` [dpdk-dev] [PATCH 03/13] mbuf: add packet_type field Bruce Richardson
2014-09-08 10:17   ` Olivier MATZ
2014-09-08 10:33     ` Yerden Zhumabekov
2014-09-08 11:17       ` Olivier MATZ
2014-09-09  3:59         ` Zhang, Helin
     [not found]           ` <540EB428.9060706@6wind.com>
2014-09-09  8:45             ` Zhang, Helin
2014-09-09  9:47             ` Richardson, Bruce
2014-09-09 15:05         ` Jim Thompson
2014-09-03 15:49 ` [dpdk-dev] [PATCH 04/13] mbuf: expand ol_flags field to 64-bits Bruce Richardson
2014-09-08 10:25   ` Olivier MATZ
2014-09-09  9:00     ` Richardson, Bruce
2014-09-03 15:49 ` [dpdk-dev] [PATCH 05/13] mbuf: introduce a flag to indicate a control mbuf Bruce Richardson
2014-09-08 11:53   ` Olivier MATZ
2014-09-03 15:49 ` [dpdk-dev] [PATCH 06/13] mbuf: minor changes for readability Bruce Richardson
2014-09-08 12:03   ` Olivier MATZ
2014-09-03 15:49 ` [dpdk-dev] [PATCH 07/13] mbuf: use macros only to access the mbuf metadata Bruce Richardson
2014-09-08 12:05   ` Olivier MATZ
2014-09-09  9:01     ` Richardson, Bruce
2014-09-12 16:56       ` Dumitrescu, Cristian
2014-09-12 21:02         ` Olivier MATZ
2014-09-16 20:07           ` Dumitrescu, Cristian
2014-09-16 22:06             ` Ramia, Kannan Babu
2014-09-17 10:31               ` Richardson, Bruce
2014-09-17 14:01                 ` Thomas Monjalon
2014-09-10 15:09     ` Bruce Richardson
2014-09-10 15:31       ` Olivier MATZ
2014-09-03 15:49 ` [dpdk-dev] [PATCH 08/13] mbuf: add named points inside the mbuf structure Bruce Richardson
2014-09-08 12:08   ` Olivier MATZ
2014-09-03 15:49 ` [dpdk-dev] [PATCH 09/13] ixgbe: rework vector pmd following mbuf changes Bruce Richardson
2014-09-03 15:49 ` [dpdk-dev] [PATCH 10/13] mbuf: split mbuf across two cache lines Bruce Richardson
2014-09-08 12:10   ` Olivier MATZ
2014-09-03 15:49 ` [dpdk-dev] [PATCH 11/13] mbuf: move l2_len and l3_len to second cache line Bruce Richardson
2014-09-04  5:08   ` Yerden Zhumabekov
2014-09-04 10:27     ` Bruce Richardson
2014-09-04 11:00       ` Yerden Zhumabekov
2014-09-04 11:55         ` Bruce Richardson
2014-09-03 15:49 ` [dpdk-dev] [PATCH 12/13] ixgbe: Fix perf regression due to moved pool ptr Bruce Richardson
2014-09-03 15:49 ` [dpdk-dev] [PATCH 13/13] ixgbe: Improve slow-path perf: vector scattered RX Bruce Richardson
2014-09-11 13:15 ` [dpdk-dev] [PATCH v2 00/13] Mbuf Structure Rework, part 2 Bruce Richardson
2014-09-11 13:15   ` [dpdk-dev] [PATCH v2 01/13] mbuf: replace data pointer by an offset Bruce Richardson
2014-09-11 13:15   ` [dpdk-dev] [PATCH v2 02/13] mbuf: reorder fields by time of use Bruce Richardson
2014-09-15  7:11     ` Liu, Jijiang
2014-09-15  8:19       ` Richardson, Bruce
2014-09-11 13:15   ` [dpdk-dev] [PATCH v2 03/13] mbuf: expand ol_flags field to 64-bits Bruce Richardson
2014-09-11 13:15   ` [dpdk-dev] [PATCH v2 04/13] mbuf: introduce a flag to indicate a control mbuf Bruce Richardson
2014-09-11 13:15   ` [dpdk-dev] [PATCH v2 05/13] mbuf: minor changes for readability Bruce Richardson
2014-09-11 13:15   ` [dpdk-dev] [PATCH v2 06/13] mbuf: use macros only to access the mbuf metadata Bruce Richardson
2014-09-11 13:15   ` [dpdk-dev] [PATCH v2 07/13] mbuf: move metadata macros to rte_port library Bruce Richardson
2014-09-11 13:15   ` [dpdk-dev] [PATCH v2 08/13] mbuf: add named points inside the mbuf structure Bruce Richardson
2014-09-11 13:15   ` [dpdk-dev] [PATCH v2 09/13] ixgbe: rework vector pmd following mbuf changes Bruce Richardson
2014-09-11 13:15   ` [dpdk-dev] [PATCH v2 10/13] mbuf: split mbuf across two cache lines Bruce Richardson
2014-09-11 13:15   ` [dpdk-dev] [PATCH v2 11/13] mbuf: move l2_len and l3_len to second cache line Bruce Richardson
2014-09-11 13:15   ` [dpdk-dev] [PATCH v2 12/13] ixgbe: Fix perf regression due to moved pool ptr Bruce Richardson
2014-09-15 16:20     ` [dpdk-dev] [PATCH v3 " Bruce Richardson
2014-09-11 13:15   ` [dpdk-dev] [PATCH v2 13/13] ixgbe: Improve slow-path perf: vector scattered RX Bruce Richardson
2014-09-17 22:35   ` [dpdk-dev] [PATCH v2 00/13] Mbuf Structure Rework, part 2 Thomas Monjalon

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