Re: 64 bit packet counters

From: Harti Brandt (brandt_at_fokus.fraunhofer.de)
Date: 11/08/03

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    Date: Sat, 8 Nov 2003 10:13:48 +0100 (CET)
To: Alex Hoff <ahoff@sandvine.com>

    On Fri, 7 Nov 2003, Alex Hoff wrote:

    AH>Hi,
    AH>
    AH>We are attempting to implement the IF-MIB, which requires the use of 64 bit
    AH>packet counters and the differentiation between multicast and broadcast
    AH>pkts. Since changing the if_data (by adding new counters and changing the
    AH>existing to u_int64) is a bad idea, does anyone have any good ideas on how
    AH>to do this? I was thinking of tacking on a new struct (lets call it
    AH>ifx_data) on at the end of the current if_net struct with the appropriate
    AH>counters (i/opacket, i/obyte, i/obcast, i/omcast). Apart from having to do a
    AH>little double counting is there any obvious pitfals with this approach? Does
    AH>anyone have an better ideas? Is there currently any plans to update the
    AH>network stack to handle this properly?

    You may lookup the discussions in the mailing lists. As far as I remember
    the problem with 64 bit counting was that this needs locks because not on
    all architectures you have atomic 64bit add operations. A simple method
    that does not involve kernel changes (and that I plan to implement in my
    snmp daemon) is to periodically monitor the counters (depending on the
    interface speed) and detect wraps in the daemon.

    harti 

    -- 
harti brandt,
http://www.fokus.fraunhofer.de/research/cc/cats/employees/hartmut.brandt/private
brandt@fokus.fraunhofer.de, harti@freebsd.org
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