diff options
| author | Alexander Lobakin <aleksander.lobakin@intel.com> | 2025-08-26 17:54:55 +0200 |
|---|---|---|
| committer | Tony Nguyen <anthony.l.nguyen@intel.com> | 2025-09-08 10:26:25 -0700 |
| commit | 17d370a70bae277678b6ea82d71ef5892e7aaa97 (patch) | |
| tree | 0110bb6e5ef7ee62b15b2e8935e71a5a1baadc28 /include/net/libeth | |
| parent | c6142e1913de563ab772f7b0e4ae78d6de9cc5b1 (diff) | |
xdp, libeth: make the xdp_init_buff() micro-optimization generic
Often times the compilers are not able to expand two consecutive 32-bit
writes into one 64-bit on the corresponding architectures. This applies
to xdp_init_buff() called for every received frame (or at least once
per each 64 frames when the frag size is fixed).
Move the not-so-pretty hack from libeth_xdp straight to xdp_init_buff(),
but using a proper union around ::frame_sz and ::flags.
The optimization is limited to LE architectures due to the structure
layout.
One simple example from idpf with the XDP series applied (Clang 22-git,
CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE => -O2):
add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-27 (-27)
Function old new delta
idpf_vport_splitq_napi_poll 5076 5049 -27
The perf difference with XDP_DROP is around +0.8-1% which I see as more
than satisfying.
Suggested-by: Simon Horman <horms@kernel.org>
Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Tested-by: Ramu R <ramu.r@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Diffstat (limited to 'include/net/libeth')
| -rw-r--r-- | include/net/libeth/xdp.h | 11 |
1 files changed, 1 insertions, 10 deletions
diff --git a/include/net/libeth/xdp.h b/include/net/libeth/xdp.h index f4880b50e804..bc3507edd589 100644 --- a/include/net/libeth/xdp.h +++ b/include/net/libeth/xdp.h @@ -1274,7 +1274,6 @@ bool libeth_xdp_buff_add_frag(struct libeth_xdp_buff *xdp, * Internal, use libeth_xdp_process_buff() instead. Initializes XDP buffer * head with the Rx buffer data: data pointer, length, headroom, and * truesize/tailroom. Zeroes the flags. - * Uses faster single u64 write instead of per-field access. */ static inline void libeth_xdp_prepare_buff(struct libeth_xdp_buff *xdp, const struct libeth_fqe *fqe, @@ -1282,17 +1281,9 @@ static inline void libeth_xdp_prepare_buff(struct libeth_xdp_buff *xdp, { const struct page *page = __netmem_to_page(fqe->netmem); -#ifdef __LIBETH_WORD_ACCESS - static_assert(offsetofend(typeof(xdp->base), flags) - - offsetof(typeof(xdp->base), frame_sz) == - sizeof(u64)); - - *(u64 *)&xdp->base.frame_sz = fqe->truesize; -#else - xdp_init_buff(&xdp->base, fqe->truesize, xdp->base.rxq); -#endif xdp_prepare_buff(&xdp->base, page_address(page) + fqe->offset, pp_page_to_nmdesc(page)->pp->p.offset, len, true); + xdp_init_buff(&xdp->base, fqe->truesize, xdp->base.rxq); } /** |