> From: Stephen Hemminger [mailto:step...@networkplumber.org] > Sent: Saturday, 12 April 2025 18.57 > > On Sat, 12 Apr 2025 11:59:10 +0200 > Morten Brørup <m...@smartsharesystems.com> wrote: > > > > From: Stephen Hemminger [mailto:step...@networkplumber.org] > > > Sent: Saturday, 12 April 2025 01.45 > > > > > > Add field to union used for sched/event etc, for use when > > > an mbuf is mirrored. > > > > > > Signed-off-by: Stephen Hemminger <step...@networkplumber.org> > > > --- > > > lib/mbuf/rte_mbuf_core.h | 8 ++++++++ > > > 1 file changed, 8 insertions(+) > > > > > > diff --git a/lib/mbuf/rte_mbuf_core.h b/lib/mbuf/rte_mbuf_core.h > > > index a0df265b5d..1806dddd67 100644 > > > --- a/lib/mbuf/rte_mbuf_core.h > > > +++ b/lib/mbuf/rte_mbuf_core.h > > > @@ -589,6 +589,14 @@ struct __rte_cache_aligned rte_mbuf { > > > * @see > > > rte_event_eth_tx_adapter_txq_set() > > > */ > > > } txadapter; /**< Eventdev ethdev Tx > > > adapter */ > > > + struct rte_mbuf_mirror { > > > + uint32_t orig_len; > > > + uint16_t queue_id; > > > + uint16_t direction; > > > + /**< Port mirroring uses this to > > > store origin > > > + * @see rte_eth_mirror() > > > + */ > > > + } mirror; > > > uint32_t usr; > > > /**< User defined tags. See > > > rte_distributor_process() */ > > > } hash; /**< hash information > > > > Stop overloading the "hash" field! > > > > We now have dynfields. The mbuf structure's dedicated fields should > be limited to absolute core features. > > > > Long term, the "hash" field should be cleaned up. > > E.g. if we get rid of the Flow Director and make the 8 byte "sched" > (Hierarchical Scheduler) a dynfield, the "hash" field can be reduced > from 8 byte to 4 byte (RSS hash). > > > > I acknowledge that some mbuf fields can be overloaded and thus used > for multiple purposes - i.e. a value only used for ingress/forwarding > (e.g. RSS hash) can share an mbuf field with a value only used for > egress (e.g. Scheduler). > > > > The overloading of the "hash" field is too much already. E.g. can the > Hierarchical Scheduler be used together with the Eventdev ethdev Tx > adapter, or are they mutually exclusive due to sharing the same mbuf > field? > > > > Going to the extreme, we would completely replace the "hash" field by > dynfields. > > > > In short: Overloading the "hash" field with port mirror information > is a step in the wrong direction. > > Short answer: Dynamic Fields are hard to work with primary/secondary > process model. > The goal was to allow dumpcap to run and just work without > modifications to the primary application. > If secondary creates dynamic field, the primary doesn't see it.
I skimmed the mbuf dynfield source code, and it looks like it is designed for primary/secondary process model. If the primary process doesn't see a dynfield created in a secondary process, it is a bug in the mbuf dynfield library. I couldn't find such a bug in Bugzilla. I would be much better to fix the bug than overloading the "hash" field. > > The hash field is not going away, flow director is stuck, it has been > scheduled for removal > for 3 years and Intel still needs it. Other uses such as storing > received hash value are > still needed. > > Long answer: > It maybe possible. The patchset went through many revisions during > development. > Ended up having to have MP server for start/stop, and if that code was > extended > to allow secondary to proxy setting up mirror, then the code in > handling mirror() on > primary could also setup the dynamic fields. But accessing dynamic > fields is slower, > not that it matters that much if we have to copy mbuf anyway. Other > option > would be to pre-pend a pseudo header that capture could then use.
