From: Olivier Matz <olivier.matz@6wind.com>
To: David Marchand <david.marchand@redhat.com>
Cc: Yongseok Koh <yskoh@mellanox.com>,
shahafs@mellanox.com, dev@dpdk.org, stable@dpdk.org
Subject: Re: [dpdk-stable] [dpdk-dev] [PATCH] net/mlx5: fix instruction hotspot on replenishing Rx buffer
Date: Wed, 9 Jan 2019 10:52:05 +0100 [thread overview]
Message-ID: <20190109095205.us53xaocvokx4jog@glumotte.dev.6wind.com> (raw)
In-Reply-To: <CAJFAV8x+WBbei_HwQeGMdb+YZw8YSEWgP4uVp0Nihewc=myEaw@mail.gmail.com>
On Wed, Jan 09, 2019 at 10:38:07AM +0100, David Marchand wrote:
> On Wed, Jan 9, 2019 at 9:54 AM Yongseok Koh <yskoh@mellanox.com> wrote:
>
> > On replenishing Rx buffers for vectorized Rx, mbuf->buf_addr isn't needed
> > to be accessed as it is static and easily calculated from the mbuf address.
> > Accessing the mbuf content causes unnecessary load stall and it is worsened
> > on ARM.
> >
> > Fixes: 545b884b1da3 ("net/mlx5: fix buffer address posting in SSE Rx")
> > Cc: stable@dpdk.org
> >
> > Signed-off-by: Yongseok Koh <yskoh@mellanox.com>
> > ---
> > drivers/net/mlx5/mlx5_rxtx_vec.h | 8 ++++++--
> > 1 file changed, 6 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/net/mlx5/mlx5_rxtx_vec.h
> > b/drivers/net/mlx5/mlx5_rxtx_vec.h
> > index fda7004e2d..ced5547307 100644
> > --- a/drivers/net/mlx5/mlx5_rxtx_vec.h
> > +++ b/drivers/net/mlx5/mlx5_rxtx_vec.h
> > @@ -102,8 +102,12 @@ mlx5_rx_replenish_bulk_mbuf(struct mlx5_rxq_data
> > *rxq, uint16_t n)
> > return;
> > }
> > for (i = 0; i < n; ++i) {
> > - wq[i].addr = rte_cpu_to_be_64((uintptr_t)elts[i]->buf_addr
> > +
> > - RTE_PKTMBUF_HEADROOM);
> > + uintptr_t buf_addr =
> > + (uintptr_t)elts[i] + sizeof(struct rte_mbuf) +
> > + rte_pktmbuf_priv_size(rxq->mp) +
> > RTE_PKTMBUF_HEADROOM;
> > +
> > + assert(buf_addr == (uintptr_t)elts[i]->buf_addr);
> > + wq[i].addr = rte_cpu_to_be_64(buf_addr);
> > /* If there's only one MR, no need to replace LKey in WQE.
> > */
> > if (unlikely(mlx5_mr_btree_len(&rxq->mr_ctrl.cache_bh) >
> > 1))
> > wq[i].lkey = mlx5_rx_mb2mr(rxq, elts[i]);
> > --
> > 2.11.0
> >
> >
> How about having a macro / inline in the mbuf api to get this information
> in a consistent/unique way ?
> I can see we have this calculation at least in rte_pktmbuf_init() and
> rte_pktmbuf_detach().
Agree. Maybe rte_mbuf_default_buf_addr(m) ?
Side note, is the assert() correct in the patch? I'd say there's a
difference of RTE_PKTMBUF_HEADROOM between the 2 values.
Olivier
next prev parent reply other threads:[~2019-01-09 9:52 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-09 8:54 [dpdk-stable] " Yongseok Koh
2019-01-09 9:38 ` [dpdk-stable] [dpdk-dev] " David Marchand
2019-01-09 9:52 ` Olivier Matz [this message]
2019-01-09 9:56 ` Yongseok Koh
2019-01-09 10:05 ` David Marchand
2019-01-09 10:11 ` Yongseok Koh
[not found] ` <20190109131908.4949-1-yskoh@mellanox.com>
2019-01-09 13:19 ` [dpdk-stable] [PATCH v2 2/2] " Yongseok Koh
[not found] ` <20190110183528.42503-1-yskoh@mellanox.com>
2019-01-10 18:35 ` [dpdk-stable] [PATCH v3 " Yongseok Koh
2019-01-10 19:10 ` [dpdk-stable] [dpdk-dev] " Shahaf Shuler
[not found] ` <20190110224030.2671-1-yskoh@mellanox.com>
2019-01-10 22:40 ` [dpdk-stable] [PATCH v4 " Yongseok Koh
[not found] ` <20190114211622.6900-1-yskoh@mellanox.com>
2019-01-14 21:16 ` [dpdk-stable] [PATCH v5 " Yongseok Koh
2019-02-06 15:54 ` [dpdk-stable] [dpdk-dev] " Kevin Traynor
2019-02-21 19:10 ` Kevin Traynor
2019-03-08 2:05 ` Yongseok Koh
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