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Date: Sat, 15 Feb 2020 23:16:35 +0800
From: Ye Xiaolong <xiaolong.ye@intel.com>
To: Gavin Hu <gavin.hu@arm.com>
Cc: dev@dpdk.org, nd@arm.com, david.marchand@redhat.com,
thomas@monjalon.net, jerinj@marvell.com,
Honnappa.Nagarahalli@arm.com, ruifeng.wang@arm.com,
phil.yang@arm.com, joyce.kong@arm.com, steve.capper@arm.com,
stable@dpdk.org
Message-ID: <20200215151635.GH16933@intel.com>
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<20200212055621.118363-1-gavin.hu@arm.com>
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Subject: Re: [dpdk-dev] [PATCH v4] net/i40e: relaxed barrier in the tx
fastpath
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s/relaxed/relax
On 02/12, Gavin Hu wrote:
>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@mail.gmail.com
>
>Fixes: 4861cde46116 ("i40e: new poll mode driver")
>Cc: stable@dpdk.org
>
>Signed-off-by: Gavin Hu <gavin.hu@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
>
Applied to dpdk-next-net-intel with Jerin's Reviewed-by tag, Thanks.