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From: Iasen Kostov <tbyte@otel.net>
To: Chih-Chang Hsieh <cch@kmu.edu.tw>
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Date: Wed, 15 Mar 2006 16:55:40 +0200
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Subject: Re: if_bridge + polling get lower througphts
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On Wed, 2006-03-15 at 18:16 +0800, Chih-Chang Hsieh wrote:
> We have a FreeBSD 6.1-PRELEASE box.
> 
> It runs with 2 em NICs and uses if_bridge + IPFW + ipfilter + pf.
> 
> This box usually gets a very high interrupt rate >90%.
> 
> By using netstat -I em0 1, we see:
> 
> input (em0) output
> packets errs bytes packets errs bytes colls
> 15164 0 9549410 16842 0 12132262 0
> 15331 0 9220723 17466 0 12354486 0
> 16486 0 10089165 17926 0 13256014 0
> 14936 10 8363433 17090 0 13367271 0
> 14712 0 8449705 16701 0 13443079 0
> 
> 
> When we enable the polling on em0 and em1 by ifconfig, netstat -I em0 shows:
> 
> input (em0) output
> packets errs bytes packets errs bytes colls
> 10910 0 6629176 11467 0 7681346 0
> 10951 0 6916042 11397 0 7954205 0
> 11281 0 7437813 10804 0 7390386 0
> 10711 0 6308033 11605 0 8400405 0
> 10807 0 6270716 10973 0 7700748 0
> 
> the interrupt rate decreases (<30%) but we get lower throuphts.
> 
> The related sysctl MIBs are:
> 
> kern.polling.idlepoll_sleeping: 1
> kern.polling.stalled: 0
> kern.polling.suspect: 0
> kern.polling.phase: 0
> kern.polling.enable: 0
> kern.polling.handlers: 0
> kern.polling.residual_burst: 0
> kern.polling.pending_polls: 0
> kern.polling.lost_polls: 0
> kern.polling.short_ticks: 0
> kern.polling.reg_frac: 20
> kern.polling.user_frac: 50
> kern.polling.idle_poll: 1
> kern.polling.each_burst: 5
> kern.polling.burst_max: 1000
> kern.polling.burst: 5
> 
> net.link.bridge.ipfw: 1
> net.link.bridge.pfil_member: 1
> net.link.bridge.pfil_bridge: 1
> net.link.bridge.pfil_onlyip: 0
> 
> How could we tune the box to reach higher throughputs
> 
> as in non-polling mode?
> 

	What is your kern.clockrate hz (sysctl kern.clockrate) ?
Probably it's to low for network card to handle the packets and that
lowers tha data rate.