In dpdk21.02, it add the cldemote feature. I see it used in the DLB eventdev driver. But I don't understand why it uses here as followed.
>static __rte_always_inline int
>dlb_recv_qe(struct dlb_port *qm_port, struct dlb_dequeue_qe *qe,
> uint8_t *offset)
>
{
> cache_line_base = (void *)(((uintptr_t)cq_addr) & ~0x3F);
> *offset = ((uintptr_t)cq_addr & 0x30) >> 4;
>
> /* Load the next CQ cache line from memory. Pack these reads as tight
> * as possible to reduce the chance that DLB invalidates the line while
> * the CPU is reading it. Read the cache line backwards to ensure that
> * if QE[N] (N > 0) is valid, then QEs[0:N-1] are too.
> *
> * (Valid QEs start at &qe[offset])
> */
> qes[3] = _mm_load_si128((__m128i *)&cache_line_base[6]);
> qes[2] = _mm_load_si128((__m128i *)&cache_line_base[4]);
> qes[1] = _mm_load_si128((__m128i *)&cache_line_base[2]);
> qes[0] = _mm_load_si128((__m128i *)&cache_line_base[0]);
>/* Evict the cache line ASAP */
>rte_cldemote(cache_line_base); // why used here ?
