[dpdk-dev] [PATCH v4] net/i40e: relaxed barrier in the tx fastpath
Gavin Hu
gavin.hu at arm.com
Wed Feb 12 06:56:21 CET 2020
To keep ordering of mixed accesses, rte_cio is sufficient.
The rte_io barrier inside the I40E_PCI_REG_WRITE is overkill.[1]
[1] http://inbox.dpdk.org/dev/CALBAE1M-ezVWCjqCZDBw+MMDEC4O9
qf0Kpn89EMdGDajepKoZQ at mail.gmail.com
Fixes: 4861cde46116 ("i40e: new poll mode driver")
Cc: stable at dpdk.org
Signed-off-by: Gavin Hu <gavin.hu at arm.com>
---
V4:
- add the Fixes tag and CC stable <Xiaolong Ye>
V3:
- optimize the barriers in the fast path only, leave as it is for the
barriers in the slow path and control path <jerin>
- drop the virtio patches from the list as they are in the control path
- it makes more sense to relax the barrier in the fast path, at the PMD level.
relaxing the fundamental rte_io_x barriers APIs requires scrutinizations for
each PMDs which use the barriers directly or indirectly.
V2:
- remove virtio_pci_read/write64 APIs definitions, they are not needed and generate compiling errors like " error: unused function 'virtio_pci_write64' [-Werror,-Wunused-function]"
- update the reference link to kernel source code
---
drivers/net/i40e/i40e_rxtx.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/net/i40e/i40e_rxtx.c b/drivers/net/i40e/i40e_rxtx.c
index fd1ae80da..8c0f7cc67 100644
--- a/drivers/net/i40e/i40e_rxtx.c
+++ b/drivers/net/i40e/i40e_rxtx.c
@@ -1248,7 +1248,8 @@ i40e_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts, uint16_t nb_pkts)
(unsigned) txq->port_id, (unsigned) txq->queue_id,
(unsigned) tx_id, (unsigned) nb_tx);
- I40E_PCI_REG_WRITE(txq->qtx_tail, tx_id);
+ rte_cio_wmb();
+ I40E_PCI_REG_WRITE_RELAXED(txq->qtx_tail, tx_id);
txq->tx_tail = tx_id;
return nb_tx;
--
2.17.1
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