[dpdk-dev] [PATCH] app/testpmd: fix txonly mode timestamp intitialization
Phil Yang
Phil.Yang at arm.com
Tue Jul 28 18:23:44 CEST 2020
> -----Original Message-----
> From: dev <dev-bounces at dpdk.org> On Behalf Of Viacheslav Ovsiienko
> Sent: Monday, July 27, 2020 11:27 PM
> To: dev at dpdk.org
> Cc: matan at mellanox.com; rasland at mellanox.com; thomas at monjalon.net;
> ferruh.yigit at 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 at 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(×tamp_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(×tamp_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, ×tamp_initial[pi]);
> + if (timestamp_enable)
> + timestamp_init_req++;
__atomic_add_fetch(×tamp_init_req, 1, __ATOMIC_ACQ_REL);
> + rte_wmb();
We can remove it now.
Thanks,
Phil
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