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mbuf: add userdata pointer field

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While some applications may store metadata about packets in the packet
mbuf headroom, this is not a workable solution for packet metadata which
is either:
* larger than the headroom (or headroom is needed for adding pkt headers)
* needs to be shared or copied among packets

To support these use cases in applications, we reserve a general
"userdata" pointer field inside the second cache-line of the mbuf. This
is better than having the application store the pointer to the external
metadata in the packet headroom, as it saves an additional cache-line
from being used.

Apart from storing metadata, this field also provides a general 8-byte
scratch space inside the mbuf for any other application uses that are
applicable.

Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
Acked-by: Pablo de Lara <pablo.de.lara.guarch@intel.com>
This commit is contained in:
Bruce Richardson 2014-09-23 12:08:16 +01:00 committed by Thomas Monjalon
parent 7f78e67701
commit 4cd917b308
2 changed files with 10 additions and 2 deletions
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6
lib/librte_eal/linuxapp/eal/include/exec-env/rte_kni_common.h
View File

@ -116,8 +116,10 @@ struct rte_kni_mbuf {
char pad2[2];
uint16_t data_len; /**< Amount of data in segment buffer. */
uint32_t pkt_len; /**< Total pkt len: sum of all segment data_len. */
char pad3[8];
void *pool __attribute__((__aligned__(64)));
/* fields on second cache line */
char pad3[8] __attribute__((__aligned__(64)));
void *pool;
void *next;
};

6
lib/librte_mbuf/rte_mbuf.h
View File

@ -172,6 +172,12 @@ struct rte_mbuf {
/* second cache line - fields only used in slow path or on TX */
MARKER cacheline1 __rte_cache_aligned;
union {
void *userdata; /**< Can be used for external metadata */
uint64_t udata64; /**< Allow 8-byte userdata on 32-bit */
};
struct rte_mempool *pool; /**< Pool from which mbuf was allocated. */
struct rte_mbuf *next; /**< Next segment of scattered packet. */