Re: [dpdk-dev] [PATCH v1] net/i40e: remove the SMP barrier in HW scanning func
From: Honnappa Nagarahalli <hidden>
Date: 2021-06-04 16:12:21
<snip>
Add the logic to determine how many DD bits have been set for contiguous packets, for removing the SMP barrier while reading descs.
Are there any performance numbers with this change?
quoted hunk ↗ jump to hunk
Signed-off-by: Joyce Kong <redacted> Reviewed-by: Ruifeng Wang <redacted> --- drivers/net/i40e/i40e_rxtx.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-)diff --git a/drivers/net/i40e/i40e_rxtx.c b/drivers/net/i40e/i40e_rxtx.c index6c58decec..410a81f30 100644--- a/drivers/net/i40e/i40e_rxtx.c +++ b/drivers/net/i40e/i40e_rxtx.c@@ -452,7 +452,7 @@ i40e_rx_scan_hw_ring(struct i40e_rx_queue *rxq) uint16_t pkt_len; uint64_t qword1; uint32_t rx_status; - int32_t s[I40E_LOOK_AHEAD], nb_dd; + int32_t s[I40E_LOOK_AHEAD], var, nb_dd; int32_t i, j, nb_rx = 0; uint64_t pkt_flags; uint32_t *ptype_tbl = rxq->vsi->adapter->ptype_tbl; @@ -482,11 +482,14 @@ i40e_rx_scan_hw_ring(struct i40e_rx_queue *rxq) I40E_RXD_QW1_STATUS_SHIFT; } - rte_smp_rmb(); - /* Compute how many status bits were set */ - for (j = 0, nb_dd = 0; j < I40E_LOOK_AHEAD; j++) - nb_dd += s[j] & (1 <<I40E_RX_DESC_STATUS_DD_SHIFT); + for (j = 0, nb_dd = 0; j < I40E_LOOK_AHEAD; j++) { + var = s[j] & (1 << I40E_RX_DESC_STATUS_DD_SHIFT); + if (var) + nb_dd += 1; + else + break; + } nb_rx += nb_dd; -- 2.17.1