netdev - Re: [PATCH v12 net-next 3/5] sched: Struct definition and parsing of dualpi2 qdisc

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Message-ID: <m2ikmvt78v.fsf@gmail.com>
Date: Wed, 23 Apr 2025 13:03:28 +0100
From: Donald Hunter <donald.hunter@...il.com>
To: chia-yu.chang@...ia-bell-labs.com
Cc: xandfury@...il.com,  netdev@...r.kernel.org,  dave.taht@...il.com,
  pabeni@...hat.com,  jhs@...atatu.com,  kuba@...nel.org,
  stephen@...workplumber.org,  xiyou.wangcong@...il.com,  jiri@...nulli.us,
  davem@...emloft.net,  edumazet@...gle.com,  horms@...nel.org,
  andrew+netdev@...n.ch,  ast@...erby.net,  liuhangbin@...il.com,
  shuah@...nel.org,  linux-kselftest@...r.kernel.org,  ij@...nel.org,
  ncardwell@...gle.com,  koen.de_schepper@...ia-bell-labs.com,
  g.white@...lelabs.com,  ingemar.s.johansson@...csson.com,
  mirja.kuehlewind@...csson.com,  cheshire@...le.com,  rs.ietf@....at,
  Jason_Livingood@...cast.com,  vidhi_goel@...le.com
Subject: Re: [PATCH v12 net-next 3/5] sched: Struct definition and parsing
 of dualpi2 qdisc

chia-yu.chang@...ia-bell-labs.com writes:

> +
> +static const struct nla_policy dualpi2_policy[TCA_DUALPI2_MAX + 1] = {
> +	[TCA_DUALPI2_LIMIT]		= NLA_POLICY_MIN(NLA_U32, 1),
> +	[TCA_DUALPI2_MEMORY_LIMIT]	= NLA_POLICY_MIN(NLA_U32, 1),
> +	[TCA_DUALPI2_TARGET]		= {.type = NLA_U32},
> +	[TCA_DUALPI2_TUPDATE]		= NLA_POLICY_MIN(NLA_U32, 1),
> +	[TCA_DUALPI2_ALPHA]		=
> +		NLA_POLICY_FULL_RANGE(NLA_U32, &dualpi2_alpha_beta_range),
> +	[TCA_DUALPI2_BETA]		=
> +		NLA_POLICY_FULL_RANGE(NLA_U32, &dualpi2_alpha_beta_range),
> +	[TCA_DUALPI2_STEP_THRESH]	= {.type = NLA_U32},
> +	[TCA_DUALPI2_STEP_PACKETS]	= {.type = NLA_U8},
> +	[TCA_DUALPI2_MIN_QLEN_STEP]	= {.type = NLA_U32},
> +	[TCA_DUALPI2_COUPLING]		= NLA_POLICY_MIN(NLA_U8, 1),
> +	[TCA_DUALPI2_DROP_OVERLOAD]	= {.type = NLA_U8},
> +	[TCA_DUALPI2_DROP_EARLY]	= {.type = NLA_U8},
> +	[TCA_DUALPI2_C_PROTECTION]	=
> +		NLA_POLICY_FULL_RANGE(NLA_U8, &dualpi2_wc_range),
> +	[TCA_DUALPI2_ECN_MASK]		= {.type = NLA_U8},
> +	[TCA_DUALPI2_SPLIT_GSO]		= {.type = NLA_U8},
> +};
> +
> +static int dualpi2_change(struct Qdisc *sch, struct nlattr *opt,
> +			  struct netlink_ext_ack *extack)
> +{
> +	struct nlattr *tb[TCA_DUALPI2_MAX + 1];
> +	struct dualpi2_sched_data *q;
> +	int old_backlog;
> +	int old_qlen;
> +	int err;
> +
> +	if (!opt)
> +		return -EINVAL;
> +	err = nla_parse_nested(tb, TCA_DUALPI2_MAX, opt, dualpi2_policy,
> +			       extack);
> +	if (err < 0)
> +		return err;
> +
> +	q = qdisc_priv(sch);
> +	sch_tree_lock(sch);
> +
> +	if (tb[TCA_DUALPI2_LIMIT]) {
> +		u32 limit = nla_get_u32(tb[TCA_DUALPI2_LIMIT]);
> +
> +		WRITE_ONCE(sch->limit, limit);
> +		WRITE_ONCE(q->memory_limit, get_memory_limit(sch, limit));
> +	}
> +
> +	if (tb[TCA_DUALPI2_MEMORY_LIMIT])
> +		WRITE_ONCE(q->memory_limit,
> +			   nla_get_u32(tb[TCA_DUALPI2_MEMORY_LIMIT]));
> +
> +	if (tb[TCA_DUALPI2_TARGET]) {
> +		u64 target = nla_get_u32(tb[TCA_DUALPI2_TARGET]);
> +
> +		WRITE_ONCE(q->pi2_target, target * NSEC_PER_USEC);
> +	}
> +
> +	if (tb[TCA_DUALPI2_TUPDATE]) {
> +		u64 tupdate = nla_get_u32(tb[TCA_DUALPI2_TUPDATE]);
> +
> +		WRITE_ONCE(q->pi2_tupdate, tupdate * NSEC_PER_USEC);
> +	}
> +
> +	if (tb[TCA_DUALPI2_ALPHA]) {
> +		u32 alpha = nla_get_u32(tb[TCA_DUALPI2_ALPHA]);
> +
> +		WRITE_ONCE(q->pi2_alpha, dualpi2_scale_alpha_beta(alpha));
> +	}
> +
> +	if (tb[TCA_DUALPI2_BETA]) {
> +		u32 beta = nla_get_u32(tb[TCA_DUALPI2_BETA]);
> +
> +		WRITE_ONCE(q->pi2_beta, dualpi2_scale_alpha_beta(beta));
> +	}
> +
> +	if (tb[TCA_DUALPI2_STEP_PACKETS]) {
> +		bool step_pkt = !!nla_get_u8(tb[TCA_DUALPI2_STEP_PACKETS]);

Would it be better to define TCA_DUALPI2_STEP_PACKETS as type NLA_FLAG
to avoid the u8 to bool conversion?

> +		u32 step_th = READ_ONCE(q->step_thresh);
> +
> +		WRITE_ONCE(q->step_in_packets, step_pkt);
> +		WRITE_ONCE(q->step_thresh,
> +			   step_pkt ? step_th : (step_th * NSEC_PER_USEC));
> +	}
> +
> +	if (tb[TCA_DUALPI2_STEP_THRESH]) {
> +		u32 step_th = nla_get_u32(tb[TCA_DUALPI2_STEP_THRESH]);
> +		bool step_pkt = READ_ONCE(q->step_in_packets);
> +
> +		WRITE_ONCE(q->step_thresh,
> +			   step_pkt ? step_th : (step_th * NSEC_PER_USEC));
> +	}
> +
> +	if (tb[TCA_DUALPI2_MIN_QLEN_STEP])
> +		WRITE_ONCE(q->min_qlen_step,
> +			   nla_get_u32(tb[TCA_DUALPI2_MIN_QLEN_STEP]));
> +
> +	if (tb[TCA_DUALPI2_COUPLING]) {
> +		u8 coupling = nla_get_u8(tb[TCA_DUALPI2_COUPLING]);
> +
> +		WRITE_ONCE(q->coupling_factor, coupling);
> +	}
> +
> +	if (tb[TCA_DUALPI2_DROP_OVERLOAD])
> +		WRITE_ONCE(q->drop_overload,
> +			   !!nla_get_u8(tb[TCA_DUALPI2_DROP_OVERLOAD]));

Type NLA_FLAG?

> +
> +	if (tb[TCA_DUALPI2_DROP_EARLY])
> +		WRITE_ONCE(q->drop_early,
> +			   !!nla_get_u8(tb[TCA_DUALPI2_DROP_EARLY]));

Type NLA_FLAG?

> +
> +	if (tb[TCA_DUALPI2_C_PROTECTION]) {
> +		u8 wc = nla_get_u8(tb[TCA_DUALPI2_C_PROTECTION]);
> +
> +		dualpi2_calculate_c_protection(sch, q, wc);
> +	}
> +
> +	if (tb[TCA_DUALPI2_ECN_MASK])
> +		WRITE_ONCE(q->ecn_mask,
> +			   nla_get_u8(tb[TCA_DUALPI2_ECN_MASK]));
> +
> +	if (tb[TCA_DUALPI2_SPLIT_GSO])
> +		WRITE_ONCE(q->split_gso,
> +			   !!nla_get_u8(tb[TCA_DUALPI2_SPLIT_GSO]));

Type NLA_FLAG?

> +
> +	old_qlen = qdisc_qlen(sch);
> +	old_backlog = sch->qstats.backlog;
> +	while (qdisc_qlen(sch) > sch->limit ||
> +	       q->memory_used > q->memory_limit) {
> +		struct sk_buff *skb = __qdisc_dequeue_head(&sch->q);
> +
> +		q->memory_used -= skb->truesize;
> +		qdisc_qstats_backlog_dec(sch, skb);
> +		rtnl_qdisc_drop(skb, sch);
> +	}
> +	qdisc_tree_reduce_backlog(sch, old_qlen - qdisc_qlen(sch),
> +				  old_backlog - sch->qstats.backlog);
> +
> +	sch_tree_unlock(sch);
> +	return 0;
> +}