Hi Jerin, Could you help review this patch? We discussed a lot on this topic and I think we agreed already to relax the barrier only on the fast path.
Best Regards, Gavin > -----Original Message----- > From: Gavin Hu <gavin...@arm.com> > Sent: Friday, February 14, 2020 3:58 PM > To: Gavin Hu <gavin...@arm.com> > Subject: Re: [dpdk-dev] [PATCH v4] net/i40e: relaxed barrier in the tx > fastpath > > 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 > qf0kpn89emdgdajepk...@mail.gmail.com > > Fixes: 4861cde46116 ("i40e: new poll mode driver") > Cc: sta...@dpdk.org > > Signed-off-by: Gavin Hu <gavin...@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 >
