netdev - Re: [PATCH iproute2 net-next v2] tc: implement support for action flags

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Date:   Mon, 4 Nov 2019 08:49:37 -0800
From:   Roopa Prabhu <roopa@...ulusnetworks.com>
To:     Vlad Buslov <vladbu@...lanox.com>
Cc:     netdev <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>,
        Jiri Pirko <jiri@...lanox.com>
Subject: Re: [PATCH iproute2 net-next v2] tc: implement support for action flags

On Wed, Oct 30, 2019 at 7:20 AM Vlad Buslov <vladbu@...lanox.com> wrote:
>
> Implement setting and printing of action flags with single available flag
> value "no_percpu" that translates to kernel UAPI TCA_ACT_FLAGS value
> TCA_ACT_FLAGS_NO_PERCPU_STATS. Update man page with information regarding
> usage of action flags.
>
> Example usage:
>
>  # tc actions add action gact drop no_percpu
>  # sudo tc actions list action gact
>  total acts 1
>
>         action order 0: gact action drop
>          random type none pass val 0
>          index 1 ref 1 bind 0
>         no_percpu

would be nice to just call it no_percpu_stats to match the flag name ?.
Current choice of word leaves room for possible conflict with other
percpu flags in the future..


>
> Signed-off-by: Vlad Buslov <vladbu@...lanox.com>
> ---
>
> Notes:
>     Changes V1 -> V2:
>
>     - Rework the change to use action API TCA_ACT_FLAGS instead of
>       per-action flags implementation.
>
>  include/uapi/linux/pkt_cls.h |  5 +++++
>  man/man8/tc-actions.8        | 14 ++++++++++++++
>  tc/m_action.c                | 19 +++++++++++++++++++
>  3 files changed, 38 insertions(+)
>
> diff --git a/include/uapi/linux/pkt_cls.h b/include/uapi/linux/pkt_cls.h
> index a6aa466fac9e..c6ad22f76ede 100644
> --- a/include/uapi/linux/pkt_cls.h
> +++ b/include/uapi/linux/pkt_cls.h
> @@ -16,9 +16,14 @@ enum {
>         TCA_ACT_STATS,
>         TCA_ACT_PAD,
>         TCA_ACT_COOKIE,
> +       TCA_ACT_FLAGS,
>         __TCA_ACT_MAX
>  };
>
> +#define TCA_ACT_FLAGS_NO_PERCPU_STATS 1 /* Don't use percpu allocator for
> +                                        * actions stats.
> +                                        */
> +
>  #define TCA_ACT_MAX __TCA_ACT_MAX
>  #define TCA_OLD_COMPAT (TCA_ACT_MAX+1)
>  #define TCA_ACT_MAX_PRIO 32
> diff --git a/man/man8/tc-actions.8 b/man/man8/tc-actions.8
> index f46166e3f685..bee59f7247fa 100644
> --- a/man/man8/tc-actions.8
> +++ b/man/man8/tc-actions.8
> @@ -47,6 +47,8 @@ actions \- independently defined actions in tc
>  ] [
>  .I COOKIESPEC
>  ] [
> +.I FLAGS
> +] [
>  .I CONTROL
>  ]
>
> @@ -71,6 +73,10 @@ ACTNAME
>  :=
>  .BI cookie " COOKIE"
>
> +.I FLAGS
> +:=
> +.I no_percpu
> +
>  .I ACTDETAIL
>  :=
>  .I ACTNAME ACTPARAMS
> @@ -186,6 +192,14 @@ As such, it can be used as a correlating value for maintaining user state.
>  The value to be stored is completely arbitrary and does not require a specific
>  format. It is stored inside the action structure itself.
>
> +.TP
> +.I FLAGS
> +Action-specific flags. Currently, the only supported flag is
> +.I no_percpu
> +which indicates that action is expected to have minimal software data-path
> +traffic and doesn't need to allocate stat counters with percpu allocator.
> +This option is intended to be used by hardware-offloaded actions.
> +
>  .TP
>  .BI since " MSTIME"
>  When dumping large number of actions, a millisecond time-filter can be
> diff --git a/tc/m_action.c b/tc/m_action.c
> index 36c744bbe374..4da810c8c0aa 100644
> --- a/tc/m_action.c
> +++ b/tc/m_action.c
> @@ -250,6 +250,16 @@ done0:
>                                 addattr_l(n, MAX_MSG, TCA_ACT_COOKIE,
>                                           &act_ck, act_ck_len);
>
> +                       if (*argv && strcmp(*argv, "no_percpu") == 0) {
> +                               struct nla_bitfield32 flags =
> +                                       { TCA_ACT_FLAGS_NO_PERCPU_STATS,
> +                                         TCA_ACT_FLAGS_NO_PERCPU_STATS };
> +
> +                               addattr_l(n, MAX_MSG, TCA_ACT_FLAGS, &flags,
> +                                         sizeof(struct nla_bitfield32));
> +                               NEXT_ARG_FWD();
> +                       }
> +
>                         addattr_nest_end(n, tail);
>                         ok++;
>                 }
> @@ -318,6 +328,15 @@ static int tc_print_one_action(FILE *f, struct rtattr *arg)
>                                            strsz, b1, sizeof(b1)));
>                 print_string(PRINT_FP, NULL, "%s", _SL_);
>         }
> +       if (tb[TCA_ACT_FLAGS]) {
> +               struct nla_bitfield32 *flags = RTA_DATA(tb[TCA_ACT_FLAGS]);
> +
> +               if (flags->selector & TCA_ACT_FLAGS_NO_PERCPU_STATS)
> +                       print_bool(PRINT_ANY, "no_percpu", "\tno_percpu",
> +                                  flags->value &
> +                                  TCA_ACT_FLAGS_NO_PERCPU_STATS);
> +               print_string(PRINT_FP, NULL, "%s", _SL_);
> +       }
>
>         return 0;
>  }
> --
> 2.21.0
>