full socket buffers

Mirek Lauš mirek.laus at gmail.com
Sat Dec 18 20:25:02 UTC 2010


On Sat, Dec 18, 2010 at 9:08 PM,  <sthaug at nethelp.no> wrote:
>> we're running ISC DHCP 4.1.1p1 on FreeBSD 7.3-RELEASE box
>> for about 30k hosts with various leasetime from 4 hours to 7 days.
>> Time to time we experience significant performance loss while
>> clients are unable to get a lease. In the time the UDP full socket
>> buffer is constantly growing:
> ...
>> How could I tell the cause of the full buffer socket?
>
> How is your disk utilization? Good ISC DHCP performance is critically
> dependent on good disk performance.
>
> We're also running 4.1.1p1, on FreeBSD 7.3-STABLE. Server hardware is
> Dell PE 1850, with two SCSI disks in a RAID-1 configuration. We have
> around 100k leases on two servers in a failover pair, with most of the
> pools on 24 hour leasetime. We don't see the problem you're seeing.
>
> Steinar Haug, Nethelp consulting, sthaug at nethelp.no
>

We're running the dhcpd service on two IBM x3550 servers in failover,
both have two 74GB 15k disks in RAID-1 so very similar to yours.

iostat sample:

[root at dhcp1 ~]# iostat 1
      tty           aacd0             cpu
 tin tout  KB/t tps  MB/s  us ni sy in id
   0  131 16.80  20  0.34  -20 -0 -1 -0 121
   0  242 16.00  19  0.30   1  0  0  0 99
   0  392 16.00  27  0.42   1  0  1  0 98
   0  155 16.00  18  0.28   1  0  0  0 98
   0  152 16.00  16  0.25   2  0  0  0 98
   0  153 16.00  23  0.36   0  0  0  0 99
   0  262 16.00   9  0.14   1  0  0  0 99
   0   43 16.00  16  0.25   1  0  0  0 99
   0   43 10.26  39  0.39   0  0  1  0 99
   0  263 16.00  22  0.34   1  0  0  0 99
   0  287 16.00   5  0.08   1  0  0  0 99
   0   43 16.00  29  0.45   1  0  0  0 99
   0  151 16.00  77  1.20   1  0  0  0 99
   0   43 16.00  26  0.41   1  0  0  0 98
   0   43 16.00  22  0.34   1  0  0  0 99
   0   43 16.00  11  0.17   0  0  0  0 100
   0   44 16.00  22  0.34   1  0  0  0 99
   0  154 16.00  29  0.45   2  0  1  0 98
   0  166 16.00  13  0.20   1  0  0  0 99
   0  209 16.00  18  0.28   1  0  0  0 99
   0   43 16.00   7  0.11   1  0  0  0 99

-m



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