[dpdk-dev] [PATCH 0/9] mbuf: structure reorganization

[Nélio Laranjeiro]

On Wed, Mar 29, 2017 at 05:56:29PM +0200, Olivier Matz wrote:
> Hi,
> 
> Does anyone have any other comment on this series?
> Can it be applied?
> 
> 
> Thanks,
> Olivier
> 
> 
> 
> On Wed,  8 Mar 2017 10:41:52 +0100, Olivier Matz <olivier.matz at 6wind.com> wrote:
> > Based on discussions done in [1] and in this thread, this patchset reorganizes
> > the mbuf.
> > 
> > The main changes are:
> > - reorder structure to increase vector performance on some non-ia
> >   platforms.
> > - 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.
> > 
> > [1] http://dpdk.org/ml/archives/dev/2016-October/049338.html
> > 
> > rfc->v1:
> > - 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(-)
> > 

Tested-by: Nelio Laranjeiro <nelio.laranjeiro at 6wind.com>

with mlx5 ConnectX-4 two ports with a single thread IO forwarding.

Olivier patches: increase performance by +0.4Mpps.
Olivier + Konstantin patches: increase performance by +0.8Mpps.

Regards,

-- 
Nélio Laranjeiro
6WIND