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Re: netdev.stats change suggestion

To: Jeff Garzik <jgarzik@xxxxxxxxxxxxxxxx>
Subject: Re: netdev.stats change suggestion
From: Robert Olsson <Robert.Olsson@xxxxxxxxxxx>
Date: Thu, 24 Jan 2002 15:25:39 +0100
Cc: Chris Wedgwood <cw@xxxxxxxx>, Dmitrii Tisnek <dima@xxxxxxxxx>, netdev@xxxxxxxxxxx, "David S. Miller" <davem@xxxxxxxxxx>
In-reply-to: <3C4FF358.B4B35B12@xxxxxxxxxxxxxxxx>
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Jeff Garzik writes:
 > > Comments?
 > 
 > With GigE you want 64-bit anyway.  Heavily loaded GigE networks will
 > turn over 32-bit counters pretty often.

 Yes 32 bit counters w. GIGE is real pain. at 5 min sampling rate byte 
 counters wraps just above 100 Mbps.

 Illstrated by a Linux GIGE router now constanly at about 200 Mbit/s

 pps counters fine they dont wrap yet :-)
 http://robur.slu.se/traffic-mrtg/archive-r1-pps.html

 To compare with were the output byte counters do wrap so they more or 
 less useless. 

 http://robur.slu.se/traffic-mrtg/archive-r1.html


 Of one decrease the sampling rate but it only very a short time solution
 and this overhead has to traded with checking carry overflow overhead.

 > Further, yet another reason is that newer NICs store the stats in 64-bit
 > numbers, in hardware.

 Yes.

 > I don't think this was discussed with DaveM, but since the SNMP MIBs use
 > 64-bit numbers and newer GigE cards use 64-bit numbers, we pretty much
 > decided at the kernel meeting that netdev_stats should go to 64-bit.

 I put my vote there too.

 Cheers.

                                                --ro  

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