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From: Yongseok Koh <yskoh@mellanox.com>
To: Olivier Matz <olivier.matz@6wind.com>
Cc: David Marchand <david.marchand@redhat.com>,
	Shahaf Shuler <shahafs@mellanox.com>,
	"dev@dpdk.org" <dev@dpdk.org>,
	"stable@dpdk.org" <stable@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH] net/mlx5: fix instruction hotspot on replenishing Rx buffer
Date: Wed, 9 Jan 2019 09:56:50 +0000
Message-ID: <45D5A06B-4014-428E-A588-6E188C87A5AA@mellanox.com> (raw)
In-Reply-To: <20190109095205.us53xaocvokx4jog@glumotte.dev.6wind.com>


> On Jan 9, 2019, at 1:52 AM, Olivier Matz <olivier.matz@6wind.com> wrote:
> 
> 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) ?

I'm also okay to add. Will come up with a new patch.

> Side note, is the assert() correct in the patch? I'd say there's a
> difference of RTE_PKTMBUF_HEADROOM between the 2 values.

Oops, my fault. Thanks for the catch, you saved a crash. :-)

Thanks,
Yongseok

  reply	other threads:[~2019-01-09  9:56 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-09  8:54 Yongseok Koh
2019-01-09  9:38 ` David Marchand
2019-01-09  9:52   ` Olivier Matz
2019-01-09  9:56     ` Yongseok Koh [this message]
2019-01-09 10:05       ` David Marchand
2019-01-09 10:11         ` Yongseok Koh
2019-01-09 13:19 ` [dpdk-dev] [PATCH v2 1/2] mbuf: add function returning default buffer address Yongseok Koh
2019-01-09 13:19   ` [dpdk-dev] [PATCH v2 2/2] net/mlx5: fix instruction hotspot on replenishing Rx buffer Yongseok Koh
2019-01-09 13:46   ` [dpdk-dev] [PATCH v2 1/2] mbuf: add function returning default buffer address David Marchand
2019-01-10  1:39     ` Rami Rosen
2019-01-10 18:18       ` Yongseok Koh
2019-01-10 18:22     ` Yongseok Koh
2019-01-10 18:35 ` [dpdk-dev] [PATCH v3 " Yongseok Koh
2019-01-10 18:35   ` [dpdk-dev] [PATCH v3 2/2] net/mlx5: fix instruction hotspot on replenishing Rx buffer Yongseok Koh
2019-01-10 19:10     ` Shahaf Shuler
2019-01-11  8:14   ` [dpdk-dev] [PATCH v3 1/2] mbuf: add function returning default buffer address Andrew Rybchenko
2019-01-11 11:03     ` Yongseok Koh
2019-01-11 11:17       ` Andrew Rybchenko
2019-01-11 11:37         ` Yongseok Koh
2019-01-11 11:57         ` Bruce Richardson
2019-01-11 12:48           ` David Marchand
2019-01-14 15:51             ` Olivier Matz
2019-01-10 22:40 ` [dpdk-dev] [PATCH v4 " Yongseok Koh
2019-01-10 22:40   ` [dpdk-dev] [PATCH v4 2/2] net/mlx5: fix instruction hotspot on replenishing Rx buffer Yongseok Koh
2019-01-11  8:05   ` [dpdk-dev] [PATCH v4 1/2] mbuf: add function returning default buffer address Olivier Matz
2019-01-11  8:11   ` David Marchand
2019-01-11  8:32     ` David Marchand
2019-01-11 11:09       ` Yongseok Koh
2019-01-11 10:25     ` Thomas Monjalon
2019-01-14 21:16 ` [dpdk-dev] [PATCH v5 1/2] mbuf: add function returning " Yongseok Koh
2019-01-14 21:16   ` [dpdk-dev] [PATCH v5 2/2] net/mlx5: fix instruction hotspot on replenishing Rx buffer Yongseok Koh
2019-02-06 15:54     ` Kevin Traynor
2019-02-21 19:10       ` Kevin Traynor
2019-03-08  2:05         ` Yongseok Koh
2019-01-15  1:35   ` [dpdk-dev] [PATCH v5 1/2] mbuf: add function returning buffer address Thomas Monjalon

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