This RFC proposes an optional shared tbl8 pool for FIB/FIB6,
to address the difficulty of sizing num_tbl8 upfront.
In practice, tbl8 usage depends on prefix distribution and
evolves over time. In multi-VRF environments, some VRFs are
elephants (full table, thousands of tbl8 groups) while others
consume very little (mostly /24 or shorter). Per-FIB sizing
forces each instance to provision for its worst case, leading
to significant memory waste.
A shared pool solves this: all FIBs draw from the same tbl8
memory, so elephant VRFs use what they need while light VRFs
cost almost nothing. The sharing granularity is flexible: one pool per
VRF, per address family, a global pool, or no sharing at all.
This series adds:
- A shared tbl8 pool, replacing per-backend allocation
(bitmap in dir24_8, stack in trie) with a common
refcounted O(1) stack allocator.
- An optional resizable mode (grow via alloc + copy + QSBR
synchronize), removing the need to guess peak usage at
creation time.
- A stats API (rte_fib_tbl8_pool_get_stats()) exposing
used/total/max counters.
All features are opt-in:
- Existing per-FIB allocation remains the default.
- Shared pool is enabled via the tbl8_pool config field.
- Resize is enabled by setting max_tbl8 > 0 with QSBR.
Shrinking (reducing pool capacity after usage drops) is not
part of this series. It would always be best-effort since
there is no compaction: if any tbl8 group near the end of the
pool is still in use, the pool cannot shrink. The current LIFO
free-list makes this less likely by immediately reusing freed
high indices, which prevents a contiguous free tail from
forming. A different allocation strategy (e.g. a min-heap
favoring low indices) could improve shrink opportunities, but
is better addressed separately.
A working integration in Grout is available:
https://github.com/DPDK/grout/pull/581 (still a draft)
Maxime Leroy (5):
test/fib6: zero-initialize config struct
fib: share tbl8 definitions between fib and fib6
fib: add shared tbl8 pool
fib: add resizable tbl8 pool
fib: add tbl8 pool stats API
app/test/test_fib6.c | 10 +-
lib/fib/dir24_8.c | 234 ++++++++++---------------
lib/fib/dir24_8.h | 17 +-
lib/fib/fib_tbl8.h | 50 ++++++
lib/fib/fib_tbl8_pool.c | 337 ++++++++++++++++++++++++++++++++++++
lib/fib/fib_tbl8_pool.h | 113 ++++++++++++
lib/fib/meson.build | 5 +-
lib/fib/rte_fib.h | 3 +
lib/fib/rte_fib6.h | 3 +
lib/fib/rte_fib_tbl8_pool.h | 149 ++++++++++++++++
lib/fib/trie.c | 230 +++++++++---------------
lib/fib/trie.h | 15 +-
12 files changed, 844 insertions(+), 322 deletions(-)
create mode 100644 lib/fib/fib_tbl8.h
create mode 100644 lib/fib/fib_tbl8_pool.c
create mode 100644 lib/fib/fib_tbl8_pool.h
create mode 100644 lib/fib/rte_fib_tbl8_pool.h
--
2.43.0
