[ovs-dev] [PATCH v6 4/6] dpif-netdev: Add simple per pmd-thread cycles counters.

[Ethan Jackson]

Acked-by: Ethan Jackson <ethan at nicira.com>


On Tue, Apr 7, 2015 at 12:02 PM, Daniele Di Proietto
<diproiettod at vmware.com> wrote:
> The counters use x86 TSC if available (currently only with DPDK). They
> will be exposed by subsequents commits
>
> Signed-off-by: Daniele Di Proietto <diproiettod at vmware.com>
> ---
>  lib/dpif-netdev.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 55 insertions(+)
>
> diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
> index 61d9211..5ac98e8 100644
> --- a/lib/dpif-netdev.c
> +++ b/lib/dpif-netdev.c
> @@ -227,6 +227,12 @@ enum dp_stat_type {
>      DP_N_STATS
>  };
>
> +enum pmd_cycles_counter_type {
> +    PMD_CYCLES_POLLING,         /* Cycles spent polling NICs. */
> +    PMD_CYCLES_PROCESSING,      /* Cycles spent processing packets */
> +    PMD_N_CYCLES
> +};
> +
>  /* A port in a netdev-based datapath. */
>  struct dp_netdev_port {
>      struct cmap_node node;      /* Node in dp_netdev's 'ports'. */
> @@ -342,6 +348,12 @@ struct dp_netdev_pmd_stats {
>      atomic_ullong n[DP_N_STATS];
>  };
>
> +/* Contained by struct dp_netdev_pmd_thread's 'cycle' member.  */
> +struct dp_netdev_pmd_cycles {
> +    /* Indexed by PMD_CYCLES_*. */
> +    atomic_ullong n[PMD_N_CYCLES];
> +};
> +
>  /* PMD: Poll modes drivers.  PMD accesses devices via polling to eliminate
>   * the performance overhead of interrupt processing.  Therefore netdev can
>   * not implement rx-wait for these devices.  dpif-netdev needs to poll
> @@ -384,6 +396,12 @@ struct dp_netdev_pmd_thread {
>      /* Statistics. */
>      struct dp_netdev_pmd_stats stats;
>
> +    /* Cycles counters */
> +    struct dp_netdev_pmd_cycles cycles;
> +
> +    /* Used to count cicles. See 'cycles_counter_end()' */
> +    unsigned long long last_cycles;
> +
>      struct latch exit_latch;        /* For terminating the pmd thread. */
>      atomic_uint change_seq;         /* For reloading pmd ports. */
>      pthread_t thread;
> @@ -2259,6 +2277,39 @@ dp_netdev_actions_free(struct dp_netdev_actions *actions)
>      free(actions);
>  }
>
> +static inline unsigned long long
> +cycles_counter(void)
> +{
> +#ifdef DPDK_NETDEV
> +    return rte_get_tsc_cycles();
> +#else
> +    return 0;
> +#endif
> +}
> +
> +/* Fake mutex to make sure that the calls to cycles_count_* are balanced */
> +extern struct ovs_mutex cycles_counter_fake_mutex;
> +
> +/* Start counting cycles.  Must be followed by 'cycles_count_end()' */
> +static inline void
> +cycles_count_start(struct dp_netdev_pmd_thread *pmd)
> +    OVS_ACQUIRES(&cycles_counter_fake_mutex)
> +    OVS_NO_THREAD_SAFETY_ANALYSIS
> +{
> +    pmd->last_cycles = cycles_counter();
> +}
> +
> +/* Stop counting cycles and add them to the counter 'type' */
> +static inline void
> +cycles_count_end(struct dp_netdev_pmd_thread *pmd,
> +                 enum pmd_cycles_counter_type type)
> +    OVS_RELEASES(&cycles_counter_fake_mutex)
> +    OVS_NO_THREAD_SAFETY_ANALYSIS
> +{
> +    unsigned long long interval = cycles_counter() - pmd->last_cycles;
> +
> +    non_atomic_ullong_add(&pmd->cycles.n[type], interval);
> +}
>
>  static void
>  dp_netdev_process_rxq_port(struct dp_netdev_pmd_thread *pmd,
> @@ -2268,7 +2319,9 @@ dp_netdev_process_rxq_port(struct dp_netdev_pmd_thread *pmd,
>      struct dp_packet *packets[NETDEV_MAX_RX_BATCH];
>      int error, cnt;
>
> +    cycles_count_start(pmd);
>      error = netdev_rxq_recv(rxq, packets, &cnt);
> +    cycles_count_end(pmd, PMD_CYCLES_POLLING);
>      if (!error) {
>          int i;
>
> @@ -2278,7 +2331,9 @@ dp_netdev_process_rxq_port(struct dp_netdev_pmd_thread *pmd,
>          for (i = 0; i < cnt; i++) {
>              packets[i]->md = PKT_METADATA_INITIALIZER(port->port_no);
>          }
> +        cycles_count_start(pmd);
>          dp_netdev_input(pmd, packets, cnt);
> +        cycles_count_end(pmd, PMD_CYCLES_PROCESSING);
>      } else if (error != EAGAIN && error != EOPNOTSUPP) {
>          static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(1, 5);
>
> --
> 2.1.4
>
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