Hi Bruce,
On 09/03/2014 05:49 PM, Bruce Richardson wrote:
> From: Olivier Matz <olivier.matz at 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 at 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 at 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 at 6wind.com>
