At 10:13 AM 3/24/98 , Christoph Badura wrote:
>fair@clock.org (Erik E. Fair  , Timekeeper) writes:
>
>>Has anyone ever proposed sticking #ifdef's around the metering code
>>to be able to turn it off for even more efficiency?
>
>I'd guess so.
>
>>Does one or more of the SNMP MIBs define some of these counters to
>>be only 32 bits?
>
>Uhm, by default *all* SNMP counters are 32 bits.

Not true.  On media faster than 20Mb/s, counters are required to be 
64bit.

Rather than switching counters to 64-bit (except on 64-bit
platforms), it may be easier to keep counters as 32-bit shadows
and every-so often roll them into 64-bit counters.  (this can be
done by either zero'ing the 32-bit counters or keeping two 
shadow copies, alternating updates between them and rolling the
differences into 64-bit counters.

    ctr64->foo += (unsigned) (cur32->foo - last32->foo);
    ...

    memcpy(last32, cur32, sizeof(*cur32));

How fast you need to do the rollover can be computed using
if_baudrate.  This could even be done in if_watchdog so no driver
need be aware of it.
-- 
Matt Thomas               Internet:   matt@3am-software.com
3am Software Foundry      WWW URL:    http://www.3am-software.com/bio/matt/
Nashua, NH                Disclaimer: I disavow all knowledge of this message