From: "Wiles, Keith" <keith.wiles@intel.com>
To: Tom Barbette <barbette@kth.se>
Cc: dpdk-dev <dev@dpdk.org>,
"Richardson, Bruce" <bruce.richardson@intel.com>,
"Mcnamara, John" <john.mcnamara@intel.com>,
Thomas Monjalon <thomas@monjalon.net>,
"Yigit, Ferruh" <ferruh.yigit@intel.com>,
"Andrew Rybchenko" <arybchenko@solarflare.com>,
Shahaf Shuler <shahafs@mellanox.com>,
Yongseok Koh <yskoh@mellanox.com>,
"olivier.matz@6wind.com" <olivier.matz@6wind.com>
Subject: Re: [dpdk-dev] [PATCH v3 1/3] rte_ethdev: Add API function to read dev clock
Date: Thu, 25 Apr 2019 18:28:54 +0000 [thread overview]
Message-ID: <F21E9D23-9769-4AB8-B11E-1B2FF5EEB1CE@intel.com> (raw)
In-Reply-To: <20190424173424.34628-2-barbette@kth.se>
> On Apr 24, 2019, at 12:34 PM, Tom Barbette <barbette@kth.se> wrote:
>
> Add rte_eth_read_clock to read the raw clock of a devide.
>
> The main use is to get the device clock conversion co-efficients to be
> able to translate the raw clock of the timestamp field of the pkt mbuf
> to a local synced time value.
>
> This function was missing to allow users to convert the RX timestamp field
> to real time without the complexity of the rte_timesync* facility. One can
> derivate the clock frequency by calling twice read_clock and then keep a
> common time base.
>
> Signed-off-by: Tom Barbette <barbette@kth.se>
> ---
> doc/guides/nics/features.rst | 1 +
> lib/librte_ethdev/rte_ethdev.c | 13 +++++++
> lib/librte_ethdev/rte_ethdev.h | 45 ++++++++++++++++++++++++
> lib/librte_ethdev/rte_ethdev_core.h | 6 ++++
> lib/librte_ethdev/rte_ethdev_version.map | 2 ++
> lib/librte_mbuf/rte_mbuf.h | 2 ++
> 6 files changed, 69 insertions(+)
>
> diff --git a/doc/guides/nics/features.rst b/doc/guides/nics/features.rst
> index c5bf32222..025b7f812 100644
> --- a/doc/guides/nics/features.rst
> +++ b/doc/guides/nics/features.rst
> @@ -602,6 +602,7 @@ Supports Timestamp.
> * **[provides] mbuf**: ``mbuf.ol_flags:PKT_RX_TIMESTAMP``.
> * **[provides] mbuf**: ``mbuf.timestamp``.
> * **[provides] rte_eth_dev_info**: ``rx_offload_capa,rx_queue_offload_capa: DEV_RX_OFFLOAD_TIMESTAMP``.
> +* **[related] eth_dev_ops**: ``read_clock``.
>
> .. _nic_features_macsec_offload:
>
> diff --git a/lib/librte_ethdev/rte_ethdev.c b/lib/librte_ethdev/rte_ethdev.c
> index d7cfa3d53..22e35d839 100644
> --- a/lib/librte_ethdev/rte_ethdev.c
> +++ b/lib/librte_ethdev/rte_ethdev.c
> @@ -4170,6 +4170,19 @@ rte_eth_timesync_write_time(uint16_t port_id, const struct timespec *timestamp)
> timestamp));
> }
>
> +int
> +rte_eth_read_clock(uint16_t port_id, uint64_t *timestamp)
> +{
> + struct rte_eth_dev *dev;
> +
> + RTE_ETH_VALID_PORTID_OR_ERR_RET(port_id, -ENODEV);
> + dev = &rte_eth_devices[port_id];
> +
> + RTE_FUNC_PTR_OR_ERR_RET(*dev->dev_ops->read_clock, -ENOTSUP);
> + return eth_err(port_id, (*dev->dev_ops->read_clock)(dev,
> + timestamp));
> +}
> +
> int
> rte_eth_dev_get_reg_info(uint16_t port_id, struct rte_dev_reg_info *info)
> {
> diff --git a/lib/librte_ethdev/rte_ethdev.h b/lib/librte_ethdev/rte_ethdev.h
> index b8d19c69f..dfaf16a56 100644
> --- a/lib/librte_ethdev/rte_ethdev.h
> +++ b/lib/librte_ethdev/rte_ethdev.h
> @@ -3793,6 +3793,51 @@ int rte_eth_timesync_read_time(uint16_t port_id, struct timespec *time);
> */
> int rte_eth_timesync_write_time(uint16_t port_id, const struct timespec *time);
>
> +/**
> + * @warning
> + * @b EXPERIMENTAL: this API may change without prior notice.
> + *
> + * Read the current clock counter of an Ethernet device
> + *
> + * This returns the current raw clock value of an Ethernet device.
> + * The value returned here is from the same clock than the one
> + * filling timestamp field of RX packets. Therefore it can be used
> + * to compute a precise conversion of the device clock to the real time.
> + *
> + * E.g, a simple heuristic to derivate the frequency would be:
> + * uint64_t start, end;
> + * rte_eth_read_clock(port, start);
> + * rte_delay_ms(100);
> + * rte_eth_read_clock(port, end);
> + * double freq = (end - start) * 10;
> + *
> + * Compute a common reference with:
> + * uint64_t base_time_sec = current_time();
> + * uint64_t base_clock;
> + * rte_eth_read_clock(port, base_clock);
> + *
> + * Then, convert the raw mbuf timestamp with:
> + * base_time_sec + (double)(mbuf->timestamp - base_clock) / freq;
> + *
> + * This simple example will not provide a very good accuracy. One must
> + * at least measure multiple times the frequency and do a regression.
> + * To avoid deviation from the system time, the common reference can
> + * be repeated from time to time. The integer division can also be
> + * converted by a multiplication and a shift for better performance.
> + *
> + * @param port_id
> + * The port identifier of the Ethernet device.
> + * @param time
> + * Pointer to the uint64_t that holds the raw clock value.
What is a raw clock value? It took me a bit to find that it is in nano-seconds need to document that point.
> + *
> + * @return
> + * - 0: Success.
> + * - -ENODEV: The port ID is invalid.
> + * - -ENOTSUP: The function is not supported by the Ethernet driver.
> + */
> +int __rte_experimental
> +rte_eth_read_clock(uint16_t port_id, uint64_t *timestamp);
Using timestamp variable is not very descriptive and some other name needs to be used. Also in the driver it is called *clock.
Another question is why does this routine not perform the looping/delaying and calling read_clock and then return frequency instead. If you want a timestamp reading function then this one is not being described that way and I would think it should be done someplace else or should be.
> +
> /**
> * Config l2 tunnel ether type of an Ethernet device for filtering specific
> * tunnel packets by ether type.
> diff --git a/lib/librte_ethdev/rte_ethdev_core.h b/lib/librte_ethdev/rte_ethdev_core.h
> index 8f03f83f6..86806b3eb 100644
> --- a/lib/librte_ethdev/rte_ethdev_core.h
> +++ b/lib/librte_ethdev/rte_ethdev_core.h
> @@ -322,6 +322,10 @@ typedef int (*eth_timesync_write_time)(struct rte_eth_dev *dev,
> const struct timespec *timestamp);
> /**< @internal Function used to get time from the device clock */
>
> +typedef int (*eth_read_clock)(struct rte_eth_dev *dev,
> + uint64_t *timestamp);
> +/**< @internal Function used to get the current value of the device clock. */
> +
> typedef int (*eth_get_reg_t)(struct rte_eth_dev *dev,
> struct rte_dev_reg_info *info);
> /**< @internal Retrieve registers */
> @@ -496,6 +500,8 @@ struct eth_dev_ops {
> eth_timesync_read_time timesync_read_time; /** Get the device clock time. */
> eth_timesync_write_time timesync_write_time; /** Set the device clock time. */
>
> + eth_read_clock read_clock;
> +
> eth_xstats_get_by_id_t xstats_get_by_id;
> /**< Get extended device statistic values by ID. */
> eth_xstats_get_names_by_id_t xstats_get_names_by_id;
> diff --git a/lib/librte_ethdev/rte_ethdev_version.map b/lib/librte_ethdev/rte_ethdev_version.map
> index afcd25599..670e4fad5 100644
> --- a/lib/librte_ethdev/rte_ethdev_version.map
> +++ b/lib/librte_ethdev/rte_ethdev_version.map
> @@ -253,10 +253,12 @@ EXPERIMENTAL {
> rte_eth_dev_rx_intr_ctl_q_get_fd;
> rte_eth_find_next_of;
> rte_eth_find_next_sibling;
> + rte_eth_read_clock;
> rte_eth_switch_domain_alloc;
> rte_eth_switch_domain_free;
> rte_flow_conv;
> rte_flow_expand_rss;
> + rte_eth_read_clock;
> rte_mtr_capabilities_get;
> rte_mtr_create;
> rte_mtr_destroy;
> diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h
> index 68415af02..e530a96c5 100644
> --- a/lib/librte_mbuf/rte_mbuf.h
> +++ b/lib/librte_mbuf/rte_mbuf.h
> @@ -668,6 +668,8 @@ struct rte_mbuf {
>
> /** Valid if PKT_RX_TIMESTAMP is set. The unit and time reference
> * are not normalized but are always the same for a given port.
> + * Some devices allow to query rte_eth_read_clock that will return the
> + * current device timestamp.
The message here is not a good place for this detail, I would put it in the function call doc above.
> */
> uint64_t timestamp;
>
> --
> 2.17.1
>
Regards,
Keith
next prev parent reply other threads:[~2019-04-25 18:28 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-24 17:34 [dpdk-dev] [PATCH v3 0/3] Add rte_eth_read_clock API Tom Barbette
2019-04-24 17:34 ` Tom Barbette
2019-04-24 17:34 ` [dpdk-dev] [PATCH v3 1/3] rte_ethdev: Add API function to read dev clock Tom Barbette
2019-04-24 17:34 ` Tom Barbette
2019-04-25 17:08 ` Andrew Rybchenko
2019-04-25 17:08 ` Andrew Rybchenko
2019-04-25 18:28 ` Wiles, Keith [this message]
2019-04-25 18:28 ` Wiles, Keith
2019-04-26 8:13 ` Tom Barbette
2019-04-26 8:13 ` Tom Barbette
2019-04-24 17:34 ` [dpdk-dev] [PATCH v3 2/3] mlx5: Implement support for read_clock Tom Barbette
2019-04-24 17:34 ` Tom Barbette
2019-04-24 17:34 ` [dpdk-dev] [PATCH v3 3/3] rxtx_callbacks: Add support for HW timestamp Tom Barbette
2019-04-24 17:34 ` Tom Barbette
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=F21E9D23-9769-4AB8-B11E-1B2FF5EEB1CE@intel.com \
--to=keith.wiles@intel.com \
--cc=arybchenko@solarflare.com \
--cc=barbette@kth.se \
--cc=bruce.richardson@intel.com \
--cc=dev@dpdk.org \
--cc=ferruh.yigit@intel.com \
--cc=john.mcnamara@intel.com \
--cc=olivier.matz@6wind.com \
--cc=shahafs@mellanox.com \
--cc=thomas@monjalon.net \
--cc=yskoh@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
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).