Re: [dpdk-dev] [RFC v8] /net: memory interface (memif)

[Stephen Hemminger <stephen@networkplumber.org>]

On Thu, 16 May 2019 13:46:58 +0200
Jakub Grajciar <jgrajcia@cisco.com> wrote:

> +struct memif_queue {
> +	struct rte_mempool *mempool;		/**< mempool for RX packets */
> +	uint16_t in_port;			/**< port id */
> +
> +	struct pmd_internals *pmd;		/**< device internals */
> +
> +	struct rte_intr_handle intr_handle;	/**< interrupt handle */
> +
> +	/* ring info */
> +	memif_ring_type_t type;			/**< ring type */
> +	memif_ring_t *ring;			/**< pointer to ring */
> +	memif_log2_ring_size_t log2_ring_size;	/**< log2 of ring size */
> +
> +	memif_region_index_t region;		/**< shared memory region index */
> +	memif_region_offset_t ring_offset;
> +	/**< ring offset from start of shm region (ring - memif_region.addr) */
> +
> +	uint16_t last_head;			/**< last ring head */
> +	uint16_t last_tail;			/**< last ring tail */
> +
> +	/* rx/tx info */
> +	uint64_t n_pkts;			/**< number of rx/tx packets */
> +	uint64_t n_bytes;			/**< number of rx/tx bytes */
> +	uint64_t n_err;				/**< number of tx errors */
> +};
> +

The layout of this structure has lots of holes, you might want to rearrange elements.
struct memif_queue {
	struct rte_mempool *       mempool;              /*     0     8 */
	uint16_t                   in_port;              /*     8     2 */

	/* XXX 6 bytes hole, try to pack */

	struct pmd_internals *     pmd;                  /*    16     8 */
	struct rte_intr_handle     intr_handle;          /*    24 26656 */
	/* --- cacheline 416 boundary (26624 bytes) was 56 bytes ago --- */
	memif_ring_type_t          type;                 /* 26680     4 */

	/* XXX 4 bytes hole, try to pack */

	/* --- cacheline 417 boundary (26688 bytes) --- */
	memif_ring_t *             ring;                 /* 26688     8 */
	memif_log2_ring_size_t     log2_ring_size;       /* 26696     1 */

	/* XXX 1 byte hole, try to pack */

	memif_region_index_t       region;               /* 26698     2 */
	memif_region_offset_t      ring_offset;          /* 26700     4 */
	uint16_t                   last_head;            /* 26704     2 */
	uint16_t                   last_tail;            /* 26706     2 */

	/* XXX 4 bytes hole, try to pack */

	uint64_t                   n_pkts;               /* 26712     8 */
	uint64_t                   n_bytes;              /* 26720     8 */
	uint64_t                   n_err;                /* 26728     8 */

	/* size: 26736, cachelines: 418, members: 14 */
	/* sum members: 26721, holes: 4, sum holes: 15 */
	/* last cacheline: 48 bytes */
};