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Date:      Thu, 20 Sep 2012 17:09:13 +0700
From:      "Ivan Alexandrovich" <ivsan@ngs.ru>
To:        freebsd-net@freebsd.org
Subject:   Re: getting counters for a plenty of vlan ifaces
Message-ID:  <web-25413494@mx16.intranet.ru>
In-Reply-To: <20120919151806.GK85604@FreeBSD.org>
References:  <web-25219141@mx16.intranet.ru> <20120919151806.GK85604@FreeBSD.org>

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On Wed, 19 Sep 2012 19:18:06 +0400
  Gleb Smirnoff  wrote:

> That's strange. Per-minute read shouldn't induce
> large CPU load.
> 
> What snmp daemon do you use? I remember that several
> years ago net-snmp daemon from ports used a single
> linked list for all ARP entries, and thus it consumed a lot
> of CPU when receiving a single ARP change from routing
> socket.

It was net-snmp-5.3.. port.
Just checked on net-snmp-5.7.1 running on FreeBSD-9.0
and I see that things have changed significantly.

And even
# snmpbulkwalk -v2c -On -c <community>  <routerip> 1.3.6.1.2.1.4.22.1.2
running in an endless loop doesn't seem to affect
the number of context switches. Only the page faults count
grow up to 50k per second. Don't know if this metric has some
relation with router performance.

# vmstat a 1
  procs      memory      page                      faults         cpu
  r b w     avm    fre   flt  re  pi  po    fr  sr   in   sy   cs us sy id
  1 0 0   1034M   108M    99   0   0   0     0   0 17175 3814 30714  2 12 86
  0 0 0   1034M   108M     0   0   0   0   180   0 17230  945 31461  1 15 84
  1 0 0   1034M   108M 28627   0   0   0     0   0 17268 1734 30860  2 25 73
  1 0 0   1034M   108M 54835   0   0   0     0   0 17192 7084 31114  5 36 59
  0 0 0   1034M   108M 52911   0   0   0     0   0 17300 3508 31402  3 32 65
...

Thanks for the helpful message.

So my issue seems to be resolved.
I've been too naive not to recheck an old observation on
a contemporary versions. Even "/usr/sbin/arp -an" some
time ago (pre 8.0?) affected the cpu load somewhat.
Now even arp -an running continuosly seems to have
little impact on it.

Thanks,
Ivan




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