[ovs-dev] [PATCH OVS 3/4] dpif-netdev: Use the u32 instead of u64 for buckets

[William Tu]

On Thu, Apr 30, 2020 at 07:00:38PM +0800, xiangxia.m.yue at gmail.com wrote:
> From: Tonghao Zhang <xiangxia.m.yue at gmail.com>
> 
> When setting the meter rate to 4+Gbps, there is an overflow, the
> meters don't work as expected.
> 
> Cc: Ilya Maximets <i.maximets at ovn.org>
> Cc: William Tu <u9012063 at gmail.com>
> Cc: Jarno Rajahalme <jarno at ovn.org>
> Cc: Ben Pfaff <blp at ovn.org>
> Cc: Andy Zhou <azhou at ovn.org>
> Signed-off-by: Tonghao Zhang <xiangxia.m.yue at gmail.com>
> ---
>  include/openvswitch/ofp-meter.h | 2 +-
>  lib/dpif-netdev.c               | 4 ++--
>  lib/ofp-meter.c                 | 4 ++--
>  3 files changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/include/openvswitch/ofp-meter.h b/include/openvswitch/ofp-meter.h
> index 6776eae87e26..f55f89ac1a71 100644
> --- a/include/openvswitch/ofp-meter.h
> +++ b/include/openvswitch/ofp-meter.h
> @@ -37,7 +37,7 @@ struct ofputil_meter_band {
>      uint16_t type;
>      uint8_t prec_level;         /* Non-zero if type == OFPMBT_DSCP_REMARK. */
>      uint32_t rate;
> -    uint32_t burst_size;
> +    uint64_t burst_size;
>  };
>  
>  void ofputil_format_meter_band(struct ds *, enum ofp13_meter_flags,
> diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
> index 59546db6a2a2..104347d8b251 100644
> --- a/lib/dpif-netdev.c
> +++ b/lib/dpif-netdev.c
> @@ -277,7 +277,7 @@ static bool dpcls_lookup(struct dpcls *cls,
>  
>  struct dp_meter_band {
>      struct ofputil_meter_band up; /* type, prec_level, pad, rate, burst_size */
> -    uint32_t bucket; /* In 1/1000 packets (for PKTPS), or in bits (for KBPS) */
> +    uint64_t bucket; /* In 1/1000 packets (for PKTPS), or in bits (for KBPS) */

why setting to 4Gbps will overflow?
Each unit in bucket is 1kbpf, so 4Gbps is around 4M, around 2^20.

William

>      uint64_t packet_count;
>      uint64_t byte_count;
>  };
> @@ -5970,7 +5970,7 @@ dp_netdev_run_meter(struct dp_netdev *dp, struct dp_packet_batch *packets_,
>          band = &meter->bands[m];
>  
>          /* Update band's bucket. */
> -        band->bucket += delta_t * band->up.rate;
> +        band->bucket += (uint64_t)delta_t * band->up.rate;
>          band->bucket += delta_in_us * band->up.rate / 1000;
>          if (band->bucket > band->up.burst_size) {
>              band->bucket = band->up.burst_size;
> diff --git a/lib/ofp-meter.c b/lib/ofp-meter.c
> index 9ea40a0bfb63..1ac993bb028b 100644
> --- a/lib/ofp-meter.c
> +++ b/lib/ofp-meter.c
> @@ -72,7 +72,7 @@ ofputil_format_meter_band(struct ds *s, enum ofp13_meter_flags flags,
>      ds_put_format(s, " rate=%"PRIu32, mb->rate);
>  
>      if (flags & OFPMF13_BURST) {
> -        ds_put_format(s, " burst_size=%"PRIu32, mb->burst_size);
> +        ds_put_format(s, " burst_size=%"PRIu64, mb->burst_size);
>      }
>      if (mb->type == OFPMBT13_DSCP_REMARK) {
>          ds_put_format(s, " prec_level=%"PRIu8, mb->prec_level);
> @@ -703,7 +703,7 @@ parse_ofp_meter_mod_str__(struct ofputil_meter_mod *mm, char *string,
>                      return error;
>                  }
>              } else if (!strcmp(name, "burst_size")) {
> -                char *error = str_to_u32(value, &band->burst_size);
> +                char *error = str_to_u64(value, &band->burst_size);
>                  if (error) {
>                      return error;
>                  }
> -- 
> 1.8.3.1
>