[ovs-dev] [PATCH 1/1] netdev-dpdk: Fixed netdev_dpdk structure alignment

Lam, Tiago tiago.lam at intel.com
Fri Apr 27 16:01:10 UTC 2018


Thanks for this, Eelco.

(Sorry for the double email, missed the ML on the first one.)

On 25/04/2018 16:48, Eelco Chaudron wrote:
> Currently, the code tells us we have 4 pad bytes left in cacheline0
> while actually we are 8 bytes short:
> 

This was caused by commit 5e925cc ("netdev-dpdk: DPDK v17.11 upgrade"), 
where the dpdk_port_t typedef was changed from uint8_t to uint16_t, 
messing up the alignment.

> struct netdev_dpdk {
> 	union {
> 		OVS_CACHE_LINE_MARKER cacheline0;        /*           1 */
> 		struct {
> 			dpdk_port_t port_id;             /*     0     2 */
> 			_Bool      attached;             /*     2     1 */
> 			struct eth_addr hwaddr;          /*     4     6 */
> 			int        mtu;                  /*    12     4 */
> 			int        socket_id;            /*    16     4 */
> 			int        buf_size;             /*    20     4 */
> 			int        max_packet_len;       /*    24     4 */
> 			enum dpdk_dev_type type;         /*    28     4 */
> 			enum netdev_flags flags;         /*    32     4 */
> 			char *     devargs;              /*    40     8 */
> 			struct dpdk_tx_queue * tx_q;     /*    48     8 */
> 			struct rte_eth_link link;        /*    56     8 */
> 			int        link_reset_cnt;       /*    64     4 */
> 		};                                       /*          72 */
> 		uint8_t            pad9[128];            /*         128 */
> 	};                                               /*     0   128 */
> 	/* --- cacheline 2 boundary (128 bytes) --- */
> 
> Re-located one member, link_reset_cnt, and now it's one cache line:
> 
> struct netdev_dpdk {
> 	union {
> 		OVS_CACHE_LINE_MARKER cacheline0;        /*           1 */
> 		struct {
> 			dpdk_port_t port_id;             /*     0     2 */
> 			_Bool      attached;             /*     2     1 */
> 			struct eth_addr hwaddr;          /*     4     6 */
> 			int        mtu;                  /*    12     4 */
> 			int        socket_id;            /*    16     4 */
> 			int        buf_size;             /*    20     4 */
> 			int        max_packet_len;       /*    24     4 */
> 			enum dpdk_dev_type type;         /*    28     4 */
> 			enum netdev_flags flags;         /*    32     4 */
> 			int        link_reset_cnt;       /*    36     4 */
> 			char *     devargs;              /*    40     8 */
> 			struct dpdk_tx_queue * tx_q;     /*    48     8 */
> 			struct rte_eth_link link;        /*    56     8 */
> 		};                                       /*          64 */
> 		uint8_t            pad9[64];             /*          64 */
> 	};                                               /*     0    64 */
> 	/* --- cacheline 1 boundary (64 bytes) --- */
> 
> Signed-off-by: Eelco Chaudron <echaudro at redhat.com>

Acked-by: Tiago Lam <tiago.lam at intel.com>

Tiago


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