pkt_metadata_prefetch_init() is used to prefetch the packet metadata before initializing the metadata in pkt_metadata_init(). This is done for every packet in userspace datapath and is performance critical.
Commit 99fc16c0 prefetches only cachline0 and cacheline2 as the metadata part of respective cachelines will be initialized by pkt_metadata_init(). However in VXLAN case when popping the vxlan header, netdev_vxlan_pop_header() invokes pkt_metadata_init_tnl() which zeroes out metadata part of cacheline1 that wasn't prefetched earlier and causes performance degradation. By prefetching cacheline1, 9% performance improvement is observed. CC: Ben Pfaff <[email protected]> Fixes: 99fc16c0 ("Reorganize the pkt_metadata structure.") Signed-off-by: Bhanuprakash Bodireddy <[email protected]> --- lib/packets.h | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/lib/packets.h b/lib/packets.h index 461f488..2e8c0f1 100644 --- a/lib/packets.h +++ b/lib/packets.h @@ -159,7 +159,8 @@ pkt_metadata_init(struct pkt_metadata *md, odp_port_t port) } /* This function prefetches the cachelines touched by pkt_metadata_init() - * For performance reasons the two functions should be kept in sync. */ + * and pkt_metadata_init_tnl(). For performance reasons the two functions + * should be kept in sync. */ static inline void pkt_metadata_prefetch_init(struct pkt_metadata *md) { @@ -167,6 +168,10 @@ pkt_metadata_prefetch_init(struct pkt_metadata *md) * be initialized later in pkt_metadata_init(). */ OVS_PREFETCH(md->cacheline0); + /* Prefetch cacheline1 as members of this cacheline will be zeroed out + * in pkt_metadata_init_tnl(). */ + OVS_PREFETCH(md->cacheline1); + /* Prefetch cachline2 as ip_dst & ipv6_dst fields will be initialized. */ OVS_PREFETCH(md->cacheline2); } -- 2.4.11 _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
