netdev - Re: Purpose of bit shifts in tcp_get

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Date:	Sat, 19 May 2007 15:22:47 +1000
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	daniel.schaffrath@....com (Daniel Schaffrath)
Cc:	netdev@...r.kernel.org
Subject: Re: Purpose of bit shifts in tcp_get_info

Daniel Schaffrath <daniel.schaffrath@....com> wrote:
> 
> I was wondering what the purpose of the bit shifts in tcp_get_info  
> right after the jiffies conversion might be. What's the time unit  
> after that shift?
> 
>         info->tcpi_rtt = jiffies_to_usecs(tp->srtt)>>3;
>         info->tcpi_rttvar = jiffies_to_usecs(tp->mdev)>>2;
> [...]
>         info->tcpi_rcv_rtt = jiffies_to_usecs(tp->rcv_rtt_est.rtt)>>3;
> 
> Maybe somebody has a hint for me?

Checkout the comment in tcp_rtt_estimator() in net/ipv4/tcp_input.c.
It's commented in the actual struct too for srtt at least.

Cheers,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
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