netdev - Re: [PATCH v2] net-qdisc-hhf: Heavy-Hitter Filter (HHF) qdisc

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Date:	Wed, 11 Dec 2013 19:51:14 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Terry Lam <vtlam@...gle.com>
Cc:	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	Nandita Dukkipati <nanditad@...gle.com>,
	Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH v2] net-qdisc-hhf: Heavy-Hitter Filter (HHF) qdisc

On Wed, 2013-12-11 at 18:10 -0800, Terry Lam wrote:

> +static u32 hhf_time_stamp(void)
> +{
> +	return jiffies;
> +}


This is a 32 bit value (For a good reason)

> +{
> +	struct hh_flow_state *flow, *next;
> +	unsigned long now = hhf_time_stamp();

stored in a 'unsigned long'

> +
> +	if (list_empty(head))
> +		return NULL;
> +
> +	list_for_each_entry_safe(flow, next, head, flowchain) {
> +		unsigned long prev = flow->hit_timestamp + q->hhf_evict_timeout;


32bit + ...

> +
> +		if (time_before(prev, now)) {

This wont work on 64 bit arches : Wrapping wont be detected anymore.

We keep 32bit variables to lower memory usage,
this is why we have special macros in include/net/codel.h

Please make sure you test your v3 patch, there is no hurry ;)

Thanks !


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