DPDK patches and discussions
 help / color / mirror / Atom feed
From: Phil Yang <Phil.Yang@arm.com>
To: Viacheslav Ovsiienko <viacheslavo@mellanox.com>
Cc: "matan@mellanox.com" <matan@mellanox.com>,
	"rasland@mellanox.com" <rasland@mellanox.com>,
	"thomas@monjalon.net" <thomas@monjalon.net>,
	"ferruh.yigit@intel.com" <ferruh.yigit@intel.com>,
	Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>,
	nd <nd@arm.com>, "dev@dpdk.org" <dev@dpdk.org>, nd <nd@arm.com>
Subject: Re: [dpdk-dev] [PATCH] app/testpmd: fix txonly mode timestamp	intitialization
Date: Tue, 28 Jul 2020 16:23:44 +0000
Message-ID: <VE1PR08MB4640C75767113F2A5636BC5BE9730@VE1PR08MB4640.eurprd08.prod.outlook.com> (raw)
In-Reply-To: <1595863595-11344-1-git-send-email-viacheslavo@mellanox.com>

> -----Original Message-----
> From: dev <dev-bounces@dpdk.org> On Behalf Of Viacheslav Ovsiienko
> Sent: Monday, July 27, 2020 11:27 PM
> To: dev@dpdk.org
> Cc: matan@mellanox.com; rasland@mellanox.com; thomas@monjalon.net;
> ferruh.yigit@intel.com
> Subject: [dpdk-dev] [PATCH] app/testpmd: fix txonly mode timestamp
> intitialization
> 
> The testpmd application forwards data in multiple threads.
> In the txonly mode the Tx timestamps must be initialized
> on per thread basis to provide phase shift for the packet
> burst being sent. This per thread initialization was performed
> on zero value of the variable in thread local storage and
> happened only once after testpmd forwarding start. Executing
> "start" and "stop" commands did not cause thread local variables
> zeroing and wrong timestamp values were used.

I think it is too heavy to use rte_wmb() to guarantee the visibility of 'timestamp_init_req' updating for subsequent read operations.
We can use C11 atomics with explicit memory ordering instead of rte_wmb() to achieve the same goal.

> 
> Fixes: 4940344dab1d ("app/testpmd: add Tx scheduling command")
> 
> Signed-off-by: Viacheslav Ovsiienko <viacheslavo@mellanox.com>
> ---
>  app/test-pmd/txonly.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/app/test-pmd/txonly.c b/app/test-pmd/txonly.c
> index 97f4a45..415431d 100644
> --- a/app/test-pmd/txonly.c
> +++ b/app/test-pmd/txonly.c
> @@ -55,9 +55,13 @@
>  static struct rte_udp_hdr pkt_udp_hdr; /**< UDP header of tx packets. */
>  RTE_DEFINE_PER_LCORE(uint64_t, timestamp_qskew);
>  					/**< Timestamp offset per queue */
> +RTE_DEFINE_PER_LCORE(uint32_t, timestamp_idone); /**< Timestamp init
> done. */
> +
>  static uint64_t timestamp_mask; /**< Timestamp dynamic flag mask */
>  static int32_t timestamp_off; /**< Timestamp dynamic field offset */
>  static bool timestamp_enable; /**< Timestamp enable */
> +static volatile uint32_t timestamp_init_req;

If we use C11 atomic builtins for 'timestamp_init_req' accessing, the volatile key word becomes unnecessary.
Because they will generate same instructions.

> +				 /**< Timestamp initialization request. */
>  static uint64_t timestamp_initial[RTE_MAX_ETHPORTS];
> 
>  static void
> @@ -229,7 +233,8 @@
>  			rte_be64_t ts;
>  		} timestamp_mark;
> 
> -		if (unlikely(!skew)) {
> +		if (unlikely(timestamp_init_req !=

if (unlikely(__atomic_load_n(&timestamp_init_req, __ATOMIC_RELAXED) !=

> +			RTE_PER_LCORE(timestamp_idone))) {
>  			struct rte_eth_dev *dev = &rte_eth_devices[fs-
> >tx_port];
>  			unsigned int txqs_n = dev->data->nb_tx_queues;
>  			uint64_t phase = tx_pkt_times_inter * fs->tx_queue
> /
> @@ -241,6 +246,7 @@
>  			skew = timestamp_initial[fs->tx_port] +
>  			       tx_pkt_times_inter + phase;
>  			RTE_PER_LCORE(timestamp_qskew) = skew;
> +			RTE_PER_LCORE(timestamp_idone) =
> timestamp_init_req;


RTE_PER_LCORE(timestamp_idone) = __atomic_load_n(&timestamp_init_req, __ATOMIC_RELAXED);


>  		}
>  		timestamp_mark.pkt_idx = rte_cpu_to_be_16(idx);
>  		timestamp_mark.queue_idx = rte_cpu_to_be_16(fs-
> >tx_queue);
> @@ -426,6 +432,9 @@
>  			   timestamp_mask &&
>  			   timestamp_off >= 0 &&
>  			   !rte_eth_read_clock(pi, &timestamp_initial[pi]);
> +	if (timestamp_enable)
> +		timestamp_init_req++;


__atomic_add_fetch(&timestamp_init_req, 1, __ATOMIC_ACQ_REL);


> +	rte_wmb();

We can remove it now.


Thanks,
Phil

  reply	other threads:[~2020-07-28 16:24 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-27 15:26 Viacheslav Ovsiienko
2020-07-28 16:23 ` Phil Yang [this message]
2020-07-29  8:08   ` Slava Ovsiienko
2020-07-29  9:37     ` Phil Yang
2020-07-29 12:29 ` [dpdk-dev] [PATCH v2] " Viacheslav Ovsiienko
2020-07-29 14:07   ` Phil Yang
2020-07-29 15:29     ` Ferruh Yigit

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=VE1PR08MB4640C75767113F2A5636BC5BE9730@VE1PR08MB4640.eurprd08.prod.outlook.com \
    --to=phil.yang@arm.com \
    --cc=Honnappa.Nagarahalli@arm.com \
    --cc=dev@dpdk.org \
    --cc=ferruh.yigit@intel.com \
    --cc=matan@mellanox.com \
    --cc=nd@arm.com \
    --cc=rasland@mellanox.com \
    --cc=thomas@monjalon.net \
    --cc=viacheslavo@mellanox.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

DPDK patches and discussions

This inbox may be cloned and mirrored by anyone:

	git clone --mirror https://inbox.dpdk.org/dev/0 dev/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 dev dev/ https://inbox.dpdk.org/dev \
		dev@dpdk.org
	public-inbox-index dev

Example config snippet for mirrors.
Newsgroup available over NNTP:
	nntp://inbox.dpdk.org/inbox.dpdk.dev


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git