On 3/21/22 18:06, Kumar Amber wrote:
> The patch adds the subtable lookup name to the existing
> dp-extra-info mentioned below;

Thanks for the patch!  It seems even smaller than I expected.
Some comments inline.

> 
> dp-extra-info:miniflow_bits(18,4), lookup(generic)
> dp-extra-info:miniflow_bits(9,4), lookup(avx512_gather)

There should be no extra space in the output, since both
the bits and lookup method are parts of dp-extra-info.
Otherwise, it's harder to parse the flow dump.

> 
> Suggested-by: Ilya Maximets <[email protected]>
> Signed-off-by: Kumar Amber <[email protected]>
> Signed-off-by: Harry van Haaren <[email protected]>
> Co-authored-by: Harry van Haaren <[email protected]>
> ---
>  lib/dpif-netdev-lookup.c        | 10 ++++++----
>  lib/dpif-netdev-lookup.h        |  8 +++++++-
>  lib/dpif-netdev-private-dpcls.h |  3 +++
>  lib/dpif-netdev.c               | 15 ++++++++++++---
>  4 files changed, 28 insertions(+), 8 deletions(-)
> 
> diff --git a/lib/dpif-netdev-lookup.c b/lib/dpif-netdev-lookup.c
> index bd0a99abe..accf5a21b 100644
> --- a/lib/dpif-netdev-lookup.c
> +++ b/lib/dpif-netdev-lookup.c
> @@ -93,11 +93,11 @@ dpcls_subtable_set_prio(const char *name, uint8_t 
> priority)
>  }
>  
>  dpcls_subtable_lookup_func
> -dpcls_subtable_get_best_impl(uint32_t u0_bit_count, uint32_t u1_bit_count)
> +dpcls_subtable_get_best_impl(uint32_t u0_bit_count, uint32_t u1_bit_count,
> +                             const char **subtable_name_out)

For this function, the argument can be just called 'name', as there
are no other names here.

>  {
>      /* Iter over each subtable impl, and get highest priority one. */
>      int32_t prio = -1;
> -    const char *name = NULL;
>      dpcls_subtable_lookup_func best_func = NULL;
>  
>      for (int i = 0; i < ARRAY_SIZE(subtable_lookups); i++) {
> @@ -109,13 +109,15 @@ dpcls_subtable_get_best_impl(uint32_t u0_bit_count, 
> uint32_t u1_bit_count)
>              if (probed_func) {
>                  best_func = probed_func;
>                  prio = probed_prio;
> -                name = subtable_lookups[i].name;
> +                if (subtable_name_out) {
> +                    *subtable_name_out = subtable_lookups[i].name;
> +                }
>              }
>          }
>      }
>  
>      VLOG_DBG("Subtable lookup function '%s' with units (%d,%d), priority 
> %d\n",
> -             name, u0_bit_count, u1_bit_count, prio);
> +             *subtable_name_out, u0_bit_count, u1_bit_count, prio);
>  
>      /* Programming error - we must always return a valid func ptr. */
>      ovs_assert(best_func != NULL);
> diff --git a/lib/dpif-netdev-lookup.h b/lib/dpif-netdev-lookup.h
> index 59f51faa0..f39d622a9 100644
> --- a/lib/dpif-netdev-lookup.h
> +++ b/lib/dpif-netdev-lookup.h
> @@ -66,8 +66,14 @@ struct dpcls_subtable_lookup_info_t {
>  
>  int32_t dpcls_subtable_set_prio(const char *name, uint8_t priority);
>  
> +/* Retrieve the best implementation for dpcls subtable.
> + * subtable_name_out parameter is used to fetch the name of dpcls subtable
> + * selected by the function.
> + * The function can also be called with subtable_name_out as NULL.
> + */
>  dpcls_subtable_lookup_func
> -dpcls_subtable_get_best_impl(uint32_t u0_bit_count, uint32_t u1_bit_count);
> +dpcls_subtable_get_best_impl(uint32_t u0_bit_count, uint32_t u1_bit_count,
> +                             const char **subtable_name_out);
>  
>  /* Retrieve the array of lookup implementations for iteration.
>   * On error, returns a negative number.
> diff --git a/lib/dpif-netdev-private-dpcls.h b/lib/dpif-netdev-private-dpcls.h
> index 0d5da73c7..76ca5b29a 100644
> --- a/lib/dpif-netdev-private-dpcls.h
> +++ b/lib/dpif-netdev-private-dpcls.h
> @@ -93,6 +93,9 @@ struct dpcls_subtable {
>  
>      struct netdev_flow_key mask; /* Wildcards for fields (const). */
>      /* 'mask' must be the last field, additional space is allocated here. */
> +
> +    /* Holds the name of the DPCLS implementation slected. */
> +    const char *subtable_name;

'subtable_name' doesn't sound right.  It's not a name of a subtable
after all.  Maybe 'lookup_impl_name' or 'subtable_lookup_name' ?
'subtable_lookup_impl_name' might be the most correct, but it gets
too long, IMO.

>  };
>  
>  /* Iterate through netdev_flow_key TNL u64 values specified by 'FLOWMAP'. */
> diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
> index 720818e30..f667b0b67 100644
> --- a/lib/dpif-netdev.c
> +++ b/lib/dpif-netdev.c
> @@ -624,6 +624,9 @@ inline struct dpcls *
>  dp_netdev_pmd_lookup_dpcls(struct dp_netdev_pmd_thread *pmd,
>                             odp_port_t in_port);
>  
> +static inline struct dpcls_subtable *
> +dpcls_find_subtable(struct dpcls *cls, const struct netdev_flow_key *mask);
> +
>  static void dp_netdev_request_reconfigure(struct dp_netdev *dp);
>  static inline bool
>  pmd_perf_metrics_enabled(const struct dp_netdev_pmd_thread *pmd);
> @@ -4115,6 +4118,11 @@ dp_netdev_flow_add(struct dp_netdev_pmd_thread *pmd,
>                        count_1bits(flow->cr.mask->mf.map.bits[unit]));
>      }
>      ds_put_char(&extra_info, ')');
> +
> +    struct dpcls_subtable *subtable = dpcls_find_subtable(cls, &mask);
> +    ds_put_format(&extra_info, ", lookup(%s) ",

Both spaces are redundant here.

> +                  subtable->subtable_name);
> +
>      flow->dp_extra_info = ds_steal_cstr(&extra_info);
>      ds_destroy(&extra_info);
>  
> @@ -9748,8 +9756,8 @@ dpcls_create_subtable(struct dpcls *cls, const struct 
> netdev_flow_key *mask)
>       * by the PMD thread.
>       */
>      atomic_init(&subtable->lookup_func,
> -                dpcls_subtable_get_best_impl(unit0, unit1));
> -
> +                dpcls_subtable_get_best_impl(unit0, unit1,
> +                &subtable->subtable_name));
>      cmap_insert(&cls->subtables_map, &subtable->cmap_node, mask->hash);
>      /* Add the new subtable at the end of the pvector (with no hits yet) */
>      pvector_insert(&cls->subtables, subtable, 0);
> @@ -9797,7 +9805,8 @@ dpcls_subtable_lookup_reprobe(struct dpcls *cls)
>          /* Set the subtable lookup function atomically to avoid garbage data
>           * being read by the PMD thread. */
>          atomic_store_relaxed(&subtable->lookup_func,
> -                    dpcls_subtable_get_best_impl(u0_bits, u1_bits));
> +                    dpcls_subtable_get_best_impl(u0_bits, u1_bits,
> +                                                 &subtable->subtable_name));

This will change the value stored in the structure, but that will
not change the value of the 'flow->dp_extra_info' that will still
report the name of the old implementation during the flow dump.
dp_extra_info generated only once when the flow is created.  So,
you need to re-generate it here with the new name.  That's why I was
talking about protecting that pointer with RCU.

You should be able to write a test for that scenario.

>          subtables_changed += (old_func != subtable->lookup_func);
>      }
>  

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