[dpdk-dev] [PATCH 0/9] mbuf: structure reorganization
bruce.richardson at intel.com
Wed Mar 29 22:09:23 CEST 2017
On Wed, Mar 29, 2017 at 05:56:29PM +0200, Olivier Matz wrote:
> Does anyone have any other comment on this series?
> Can it be applied?
I assume all driver maintainers have done performance analysis to check
for regressions. Perhaps they can confirm this is the case.
> On Wed, 8 Mar 2017 10:41:52 +0100, Olivier Matz <olivier.matz at 6wind.com> wrote:
> > Based on discussions done in  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.
> >  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(-)
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