[ovs-dev] [PATCH 1/4] datapath: Remove recirc stack depth limit check

Pravin Shelar pshelar at nicira.com
Mon Aug 18 03:00:23 UTC 2014


On Fri, Aug 15, 2014 at 3:12 AM, Andy Zhou <azhou at nicira.com> wrote:
> Future patches will change the recirc action implementation to not
> using recursion. The stack depth detection is no longer necessary.
>
Once there is no recursion in OVS, only recursion left is recursion
due to networking stack. networking stack controls recursion by
xmit_recursion. But xmit_recursion limit is too high, So we can have
ovs specific xmit_recursion limit in compat xmit code.

> Signed-off-by: Andy Zhou <azhou at nicira.com>
> ---
>  datapath/actions.c  | 34 ++++++++++------------------------
>  datapath/datapath.c |  6 +++---
>  datapath/datapath.h |  4 ++--
>  datapath/vport.c    |  2 +-
>  4 files changed, 16 insertions(+), 30 deletions(-)
>
> diff --git a/datapath/actions.c b/datapath/actions.c
> index b16e0b2..bccf397 100644
> --- a/datapath/actions.c
> +++ b/datapath/actions.c
> @@ -816,7 +816,7 @@ static int execute_recirc(struct datapath *dp, struct sk_buff *skb,
>                 flow_key_clone(skb, &recirc_key);
>
>         flow_key_set_recirc_id(skb, nla_get_u32(a));
> -       ovs_dp_process_packet(skb, true);
> +       ovs_dp_process_packet(skb);
>         return 0;
>  }
>
> @@ -904,18 +904,11 @@ static int do_execute_actions(struct datapath *dp, struct sk_buff *skb,
>  }
>
>  /* We limit the number of times that we pass into execute_actions()
> - * to avoid blowing out the stack in the event that we have a loop.
> - *
> - * Each loop adds some (estimated) cost to the kernel stack.
> - * The loop terminates when the max cost is exceeded.
> - * */
> -#define RECIRC_STACK_COST 1
> -#define DEFAULT_STACK_COST 4
> -/* Allow up to 4 regular services, and up to 3 recirculations */
> -#define MAX_STACK_COST (DEFAULT_STACK_COST * 4 + RECIRC_STACK_COST * 3)
> + *  * to avoid blowing out the stack in the event that we have a loop. */
> +#define MAX_LOOPS 4
>
>  struct loop_counter {
> -       u8 stack_cost;          /* loop stack cost. */
> +       u8 count;               /* Count. */
>         bool looping;           /* Loop detected? */
>  };
>
> @@ -924,24 +917,22 @@ static DEFINE_PER_CPU(struct loop_counter, loop_counters);
>  static int loop_suppress(struct datapath *dp, struct sw_flow_actions *actions)
>  {
>         if (net_ratelimit())
> -               pr_warn("%s: flow loop detected, dropping\n",
> -                               ovs_dp_name(dp));
> +               pr_warn("%s: flow looped %d times, dropping\n",
> +                               ovs_dp_name(dp), MAX_LOOPS);
>         actions->actions_len = 0;
>         return -ELOOP;
>  }
>
>  /* Execute a list of actions against 'skb'. */
> -int ovs_execute_actions(struct datapath *dp, struct sk_buff *skb, bool recirc)
> +int ovs_execute_actions(struct datapath *dp, struct sk_buff *skb)
>  {
>         struct sw_flow_actions *acts = rcu_dereference(OVS_CB(skb)->flow->sf_acts);
> -       const u8 stack_cost = recirc ? RECIRC_STACK_COST : DEFAULT_STACK_COST;
>         struct loop_counter *loop;
>         int error;
>
>         /* Check whether we've looped too much. */
>         loop = &__get_cpu_var(loop_counters);
> -       loop->stack_cost += stack_cost;
> -       if (unlikely(loop->stack_cost > MAX_STACK_COST))
> +       if (unlikely(++loop->count > MAX_LOOPS))
>                 loop->looping = true;
>         if (unlikely(loop->looping)) {
>                 error = loop_suppress(dp, acts);
> @@ -951,14 +942,9 @@ int ovs_execute_actions(struct datapath *dp, struct sk_buff *skb, bool recirc)
>
>         error = do_execute_actions(dp, skb, acts->actions, acts->actions_len);
>
> -       /* Check whether sub-actions looped too much. */
> -       if (unlikely(loop->looping))
> -               error = loop_suppress(dp, acts);
> -
>  out_loop:
> -       /* Decrement loop stack cost. */
> -       loop->stack_cost -= stack_cost;
> -       if (!loop->stack_cost)
> +       /* Decrement loop counter. */
> +       if (!--loop->count)
>                 loop->looping = false;
>
>         return error;
> diff --git a/datapath/datapath.c b/datapath/datapath.c
> index 6131b2a..e477c72 100644
> --- a/datapath/datapath.c
> +++ b/datapath/datapath.c
> @@ -251,7 +251,7 @@ void ovs_dp_detach_port(struct vport *p)
>  }
>
>  /* Must be called with rcu_read_lock. */
> -void ovs_dp_process_packet(struct sk_buff *skb, bool recirc)
> +void ovs_dp_process_packet(struct sk_buff *skb)
>  {
>         const struct vport *p = OVS_CB(skb)->input_vport;
>         struct sw_flow_key *pkt_key = OVS_CB(skb)->pkt_key;
> @@ -281,7 +281,7 @@ void ovs_dp_process_packet(struct sk_buff *skb, bool recirc)
>         OVS_CB(skb)->flow = flow;
>
>         ovs_flow_stats_update(OVS_CB(skb)->flow, pkt_key->tp.flags, skb);
> -       ovs_execute_actions(dp, skb, recirc);
> +       ovs_execute_actions(dp, skb);
>         stats_counter = &stats->n_hit;
>
>  out:
> @@ -566,7 +566,7 @@ static int ovs_packet_cmd_execute(struct sk_buff *skb, struct genl_info *info)
>         OVS_CB(packet)->input_vport = input_vport;
>
>         local_bh_disable();
> -       err = ovs_execute_actions(dp, packet, false);
> +       err = ovs_execute_actions(dp, packet);
>         local_bh_enable();
>         rcu_read_unlock();
>
> diff --git a/datapath/datapath.h b/datapath/datapath.h
> index cd2acbc..4874ab5 100644
> --- a/datapath/datapath.h
> +++ b/datapath/datapath.h
> @@ -188,7 +188,7 @@ extern struct notifier_block ovs_dp_device_notifier;
>  extern struct genl_family dp_vport_genl_family;
>  extern struct genl_multicast_group ovs_dp_vport_multicast_group;
>
> -void ovs_dp_process_packet(struct sk_buff *, bool recirc);
> +void ovs_dp_process_packet(struct sk_buff *c);
>  void ovs_dp_detach_port(struct vport *);
>  int ovs_dp_upcall(struct datapath *, struct sk_buff *,
>                   const struct dp_upcall_info *);
> @@ -197,7 +197,7 @@ const char *ovs_dp_name(const struct datapath *dp);
>  struct sk_buff *ovs_vport_cmd_build_info(struct vport *, u32 portid, u32 seq,
>                                          u8 cmd);
>
> -int ovs_execute_actions(struct datapath *dp, struct sk_buff *skb, bool recirc);
> +int ovs_execute_actions(struct datapath *dp, struct sk_buff *skb);
>  void ovs_dp_notify_wq(struct work_struct *work);
>
>  #define OVS_NLERR(fmt, ...)                                    \
> diff --git a/datapath/vport.c b/datapath/vport.c
> index c44182c..4c68bae 100644
> --- a/datapath/vport.c
> +++ b/datapath/vport.c
> @@ -495,7 +495,7 @@ void ovs_vport_receive(struct vport *vport, struct sk_buff *skb,
>                 return;
>         }
>
> -       ovs_dp_process_packet(skb, false);
> +       ovs_dp_process_packet(skb);
>  }
>
>  /**
> --
> 1.9.1
>
> _______________________________________________
> dev mailing list
> dev at openvswitch.org
> http://openvswitch.org/mailman/listinfo/dev



More information about the dev mailing list