RE: [RFC PATCH 1/4] fib: add multi-VRF support

[Konstantin Ananyev <konstantin.ananyev@huawei.com>]

> >> Add VRF (Virtual Routing and Forwarding) support to the IPv4
> >> FIB library, allowing multiple independent routing tables
> >> within a single FIB instance.
> >>
> >> Introduce max_vrfs and vrf_default_nh fields in rte_fib_conf
> >> to configure the number of VRFs and per-VRF default nexthops.
> > Thanks Vladimir, allowing multiple VRFs per same LPM table will
> > definitely be a useful thing to have.
> > Though, I have the same concern as Maxime:
> > memory requirements are just overwhelming.
> > Stupid q - why just not to store a pointer to a vector of next-hops
> > within the table entry?
> 
> Am I understand correctly, a vector with max_number_of_vrfs entries and
> use vrf id to address a nexthop?

Yes.

> Yes, this may work.
> But, if we are going to do an extra memory access, I'd better to
> maintain an internal hash table with 5 byte keys {24_bits_from_LPM,
> 16_bits_vrf_id} to retrieve a nexthop.

Hmm... and what to do with entries in tbl8, I mean what will be the key for them?
Or you don't plan to put entries from tbl8 to that hash table?

> > And we can provide to the user with ability to specify custom
> > alloc/free function for these vectors.
> > That would help to avoid allocating huge chunks of memory at startup.
> > I understand that it will be one extra memory dereference,
> > but probably it will be not that critical in terms of performance .
> > Again for bulk function  we might be able to pipeline lookups and
> > de-references and hide that extra load latency.
> >
> >> Add four new experimental APIs:
> >> - rte_fib_vrf_add() and rte_fib_vrf_delete() to manage routes
> >>    per VRF
> >> - rte_fib_vrf_lookup_bulk() for multi-VRF bulk lookups
> >> - rte_fib_vrf_get_rib() to retrieve a per-VRF RIB handle
> >>
> >> Signed-off-by: Vladimir Medvedkin <vladimir.medvedkin@intel.com>
> >> ---
> >>   lib/fib/dir24_8.c        | 241 ++++++++++++++++------
> >>   lib/fib/dir24_8.h        | 255 ++++++++++++++++--------
> >>   lib/fib/dir24_8_avx512.c | 420 +++++++++++++++++++++++++++++++--------
> >>   lib/fib/dir24_8_avx512.h |  80 +++++++-
> >>   lib/fib/rte_fib.c        | 158 ++++++++++++---
> >>   lib/fib/rte_fib.h        |  94 ++++++++-
> >>   6 files changed, 988 insertions(+), 260 deletions(-)
> >>
> <snip>
> 
> --
> Regards,
> Vladimir
>