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 at intel.com> --- lib/librte_eal/linuxapp/eal/include/exec-env/rte_kni_common.h | 3 ++- lib/librte_mbuf/rte_mbuf.h | 3 +++ 2 files changed, 5 insertions(+), 1 deletion(-) diff --git a/lib/librte_eal/linuxapp/eal/include/exec-env/rte_kni_common.h b/lib/librte_eal/linuxapp/eal/include/exec-env/rte_kni_common.h index 25ed672..d27e891 100644 --- a/lib/librte_eal/linuxapp/eal/include/exec-env/rte_kni_common.h +++ b/lib/librte_eal/linuxapp/eal/include/exec-env/rte_kni_common.h @@ -117,7 +117,8 @@ struct rte_kni_mbuf { 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))); + void *pad4 __attribute__((__aligned__(64))); + void *pool; void *next; }; diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h index 8e27d2e..b1acfc3 100644 --- a/lib/librte_mbuf/rte_mbuf.h +++ b/lib/librte_mbuf/rte_mbuf.h @@ -172,6 +172,9 @@ struct rte_mbuf { /* second cache line - fields only used in slow path or on TX */ MARKER cacheline1 __rte_cache_aligned; + + void *userdata; /**< Can be used for external metadata */ + struct rte_mempool *pool; /**< Pool from which mbuf was allocated. */ struct rte_mbuf *next; /**< Next segment of scattered packet. */ -- 1.9.3