[dpdk-dev] [PATCH v6 0/4] LPM4 memory ordering changes

[Ruifeng Wang <ruifeng.wang@arm.com>]

LPM4 uses DIR24-8 method of routing info data organization.
Routing rule with prefix longer than 24 bits will be stored
in a tbl24 entry together with an associated tbl8 group.

When a tbl8 group is getting attached to a tbl24 entry, lookup
might fail even though the entry is configured in the table.

For ex: consider a LPM table configured with 10.10.10.1/24.
When a new entry 10.10.10.32/28 is being added, a new tbl8
group is allocated and tbl24 entry is changed to point to
the tbl8 group. If the tbl24 entry is written without the tbl8
group entries updated, a lookup on 10.10.10.9 will return
failure.

Correct memory orderings are required to ensure that the
store to tbl24 does not happen before the stores to tbl8 group
entries complete.

When memory orderings are imposed, API performance could drop.
However, a patch to de-inline unnecessary functions is added,
and this helps to keep API performance.

On Arm A72 platform, the whole patch series in general have no
notable performance impact.

On x86 E5-2640 platform, the whole patch series showed 2.6%
performance improvement on add, and no impact on lookup or
delete.


v6:
Merge multiple relaxed atomic store patches into one.
v5:
Fix typo in commit message.
Remove all other inlines.
Change to use atomic_store in tbl8_alloc / tbl8_free.
Merge multiple sigle field updates into one atomic store.
v4:
Change alignment attribute parameter.
Use atomic store to avoid partial update.
v3:
Use __rte_noinline to force no inline.
v2:
Fix clang building issue by supplying alignment attribute.

Ruifeng Wang (4):
  lib/lpm: not inline unnecessary functions
  lib/lpm: memory orderings to avoid race conditions for v1604
  lib/lpm: memory orderings to avoid race conditions for v20
  lib/lpm: use atomic store to avoid partial update

 lib/librte_lpm/rte_lpm.c | 248 ++++++++++++++++++++++++++++-----------
 lib/librte_lpm/rte_lpm.h |   8 +-
 2 files changed, 183 insertions(+), 73 deletions(-)

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2.17.1