[dpdk-dev] [PATCH 0/9] mbuf: structure reorganization
olivier.matz at 6wind.com
Wed Mar 8 10:41:52 CET 2017
Based on discussions done in  and in this thread, this patchset reorganizes
The main changes are:
- reorder structure to increase vector performance on some non-ia
- add a 64bits timestamp field in the 1st cache line. This timestamp
is not normalized, i.e. no unit or time reference is enforced. A
library may be added to do this job in the future.
- m->next, m->nb_segs, and m->refcnt are always initialized for mbufs
in the pool, avoiding the need of setting m->next (located in the
2nd cache line) in the Rx path for mono-segment packets.
- change port and nb_segs to 16 bits
- move seqn in the 2nd cache line
Things discussed but not done in the patchset:
- move refcnt and nb_segs to the 2nd cache line: many drivers sets
them in the Rx path, so it could introduce a performance regression, or
it would require to change all the drivers, which is not an easy task.
- remove the m->port field: too much impact on many examples and libraries,
and some people highlighted they are using it.
- moving m->next in the 1st cache line: there is not enough room, and having
it set to NULL for unused mbuf should remove the need for it.
- merge seqn and timestamp together in a union: we could imagine use cases
were both are activated. There is no flag indicating the presence of seqn,
so it looks preferable to keep them separated for now.
I made some basic performance tests (ixgbe) and see no regression.
Other tests from NIC vendors are welcome.
Once this patchset is pushed, the Rx path of drivers could be optimized a bit,
by removing writes to m->next, m->nb_segs and m->refcnt. The patch 4/8 gives an
idea of what could be done.
- fix reset of mbuf fields in case of indirect mbuf in rte_pktmbuf_prefree_seg()
- do not enforce a unit or time reference for m->timestamp
- reorganize fields to make vlan and outer vlan consecutive
- enhance documentation of m->refcnt and m->port to explain why they are 16bits
Jerin Jacob (1):
mbuf: make rearm data address naturally aligned
Olivier Matz (8):
mbuf: make segment prefree function public
mbuf: make raw free function public
mbuf: set mbuf fields while in pool
drivers/net: don't touch mbuf next or nb segs on Rx
mbuf: use 2 bytes for port and nb segments
mbuf: move sequence number in second cache line
mbuf: add a timestamp field
mbuf: reorder VLAN tci and buffer len fields
app/test-pmd/csumonly.c | 4 +-
drivers/net/ena/ena_ethdev.c | 2 +-
drivers/net/enic/enic_rxtx.c | 2 +-
drivers/net/fm10k/fm10k_rxtx.c | 6 +-
drivers/net/fm10k/fm10k_rxtx_vec.c | 9 +-
drivers/net/i40e/i40e_rxtx_vec_common.h | 6 +-
drivers/net/i40e/i40e_rxtx_vec_sse.c | 11 +-
drivers/net/ixgbe/ixgbe_rxtx.c | 10 +-
drivers/net/ixgbe/ixgbe_rxtx_vec_common.h | 6 +-
drivers/net/ixgbe/ixgbe_rxtx_vec_neon.c | 9 --
drivers/net/ixgbe/ixgbe_rxtx_vec_sse.c | 9 --
drivers/net/mlx5/mlx5_rxtx.c | 11 +-
drivers/net/mpipe/mpipe_tilegx.c | 3 +-
drivers/net/null/rte_eth_null.c | 2 -
drivers/net/virtio/virtio_rxtx.c | 4 -
drivers/net/virtio/virtio_rxtx_simple.h | 6 +-
.../linuxapp/eal/include/exec-env/rte_kni_common.h | 5 +-
lib/librte_mbuf/rte_mbuf.c | 4 +
lib/librte_mbuf/rte_mbuf.h | 123 ++++++++++++++++-----
19 files changed, 130 insertions(+), 102 deletions(-)
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