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Date: Wed, 6 Nov 2024 10:10:02 +0100
From: Pablo Neira Ayuso <pablo@netfilter.org>
To: Florian Westphal <fw@strlen.de>
Cc: Nadia Pinaeva <n.m.pinaeva@gmail.com>, netfilter-devel@vger.kernel.org,
	Antonio Ojea <antonio.ojea.garcia@gmail.com>
Subject: Re: [PATCH nf-next v2] netfilter: conntrack: collect start time as
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On Wed, Nov 06, 2024 at 09:34:38AM +0100, Florian Westphal wrote:
> Pablo Neira Ayuso <pablo@netfilter.org> wrote:
> > > Can you clarify?  Do you mean skb_tstamp() vs ktime_get_real_ns()
> > > or tstamp sampling in general?
> > 
> > I am referring to ktime_get_real_ns(), I remember to have measured
> > 25%-30% performance drop when this is used, but I have not refreshed
> > those numbers for long time.
> >
> > As for skb_tstamp(), I have to dig in the cost of it.
> 
> Its not about the cost, its about the sampling method.
> If skb has the rx timestamp, then the event will reflect the skb
> creation/rx time, not the "event time".  Did that make sense?

I think ktime_get_real_ns() needs to be used to get the "event time",
I am afraid skb_tstamp() is not useful.