[PATCH v12 0/3] net: optimize raw checksum computation

scott.k.mitch1
2026-01-10T01:57:07Z

From: Scott Mitchell <scott.k.mitch1@gmail.com>

This series optimizes __rte_raw_cksum() by replacing memcpy-based access
with unaligned_uint16_t pointer access, enabling vectorization in both
GCC and Clang. The series is split into three patches to clearly separate
the core optimization from compiler-specific workarounds.

Performance improvement from cksum_perf_autotest on Intel Xeon
(Cascade Lake, AVX-512) with Clang 18.1 (TSC cycles/byte):

Block size Before After Improvement
100 0.40 0.24 ~40%
1500 0.50 0.06 ~8x
9000 0.49 0.06 ~8x

Changes in v12:
- Split into 3-patch series per reviewer feedback
- Patch 1/3: Core optimization and test additions
- Patch 2/3: UBSAN alignment workaround (separate from GCC bug)
- Patch 3/3: GCC optimization bug workaround
- Reverted len & 1 to len % 2 and restored unlikely() per feedback
- Renamed RTE_SUPPRESS_UNINITIALIZED_WARNING to RTE_FORCE_INIT_BARRIER
- Applied minimal changes (no refactoring) to existing code
- Deferred hinic driver refactoring to future series

Note: Patch 1/3 will trigger compiler warnings/failures on GCC versions
with the optimization bug (GCC 11.5.0 and others seen on DPDK CI). These
are resolved by patches 2/3 and 3/3.

Scott Mitchell (3):
net: optimize __rte_raw_cksum and add tests
eal: add workaround for UBSAN alignment false positive
eal/net: add workaround for GCC optimization bug

app/test/meson.build | 1 +
app/test/test_cksum_fuzz.c | 240 +++++++++++++++++++++++++++++++
app/test/test_cksum_perf.c | 2 +-
drivers/net/hinic/hinic_pmd_tx.c | 2 +
drivers/net/mlx5/mlx5_flow_dv.c | 2 +
lib/eal/include/rte_common.h | 23 +++
lib/net/rte_cksum.h | 15 +-
lib/net/rte_ip4.h | 1 +
lib/net/rte_ip6.h | 1 +
9 files changed, 277 insertions(+), 10 deletions(-)
create mode 100644 app/test/test_cksum_fuzz.c

--
2.39.5 (Apple Git-154)