netdev - Re: [PATCH net-next v5 1/2] net/sched: transition act

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Date:   Tue, 31 Jan 2023 17:07:13 +0100
From:   Simon Horman <simon.horman@...igine.com>
To:     Pedro Tammela <pctammela@...atatu.com>
Cc:     netdev@...r.kernel.org, jhs@...atatu.com, xiyou.wangcong@...il.com,
        jiri@...nulli.us, davem@...emloft.net, edumazet@...gle.com,
        kuba@...nel.org, pabeni@...hat.com
Subject: Re: [PATCH net-next v5 1/2] net/sched: transition act_pedit to rcu
 and percpu stats

On Tue, Jan 31, 2023 at 11:51:48AM -0300, Pedro Tammela wrote:
> The software pedit action didn't get the same love as some of the
> other actions and it's still using spinlocks and shared stats in the
> datapath.
> Transition the action to rcu and percpu stats as this improves the
> action's performance dramatically on multiple cpu deployments.
> 
> Reviewed-by: Jamal Hadi Salim <jhs@...atatu.com>
> Signed-off-by: Pedro Tammela <pctammela@...atatu.com>

...

> diff --git a/net/sched/act_pedit.c b/net/sched/act_pedit.c
> index a0378e9f0121..674b534be46e 100644
> --- a/net/sched/act_pedit.c
> +++ b/net/sched/act_pedit.c

...

> @@ -143,8 +154,7 @@ static int tcf_pedit_init(struct net *net, struct nlattr *nla,
>  	bool bind = flags & TCA_ACT_FLAGS_BIND;
>  	struct nlattr *tb[TCA_PEDIT_MAX + 1];
>  	struct tcf_chain *goto_ch = NULL;
> -	struct tc_pedit_key *keys = NULL;
> -	struct tcf_pedit_key_ex *keys_ex;
> +	struct tcf_pedit_parms *oparms, *nparms;

nit: reverse xmas tree

>  	struct tc_pedit *parm;
>  	struct nlattr *pattr;
>  	struct tcf_pedit *p;

...

> @@ -212,48 +228,51 @@ static int tcf_pedit_init(struct net *net, struct nlattr *nla,
>  		ret = err;
>  		goto out_release;
>  	}
> -	p = to_pedit(*a);
> -	spin_lock_bh(&p->tcf_lock);
>  
> -	if (ret == ACT_P_CREATED ||
> -	    (p->tcfp_nkeys && p->tcfp_nkeys != parm->nkeys)) {
> -		keys = kmalloc(ksize, GFP_ATOMIC);
> -		if (!keys) {
> -			spin_unlock_bh(&p->tcf_lock);
> -			ret = -ENOMEM;
> -			goto put_chain;
> -		}
> -		kfree(p->tcfp_keys);
> -		p->tcfp_keys = keys;
> -		p->tcfp_nkeys = parm->nkeys;
> +	nparms->tcfp_off_max_hint = 0;
> +	nparms->tcfp_flags = parm->flags;
> +	nparms->tcfp_nkeys = parm->nkeys;
> +
> +	nparms->tcfp_keys = kmalloc(ksize, GFP_KERNEL);

Can ksize be zero?

...