FW: Performance issue ( maybe ) corrected
dhcp1 at thehobsons.co.uk
Fri Sep 3 15:36:54 UTC 2010
Bjarne Blichfeldt wrote:
>During the problem I see something like (numbers added from memory):
>Cpu0 : 0.0%us, 0.0%sy, 0.0%ni,100.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
>Cpu1 : 0.3%us, 0.3%sy, 0.0%ni, 99.3%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
>è Cpu2 : 0.0%us, 0.3%sy, 0.0%ni, 1.3%id, 98%wa, 0.0%hi, 0.0%si, 0.0%st
>Cpu3 : 0.0%us, 0.0%sy, 0.0%ni,100.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
>Mem: 2075208k total, 714656k used, 1360552k free, 189160k buffers
>Swap: 4128760k total, 100k used, 4128660k free, 318604k cached
>The next I have done is to increase default lease time from 8 hours to 5 days.
>around 7500 active leases
That works out at one lease renewal every around
1.5 to 2 seconds, not exactly a heavy load.
However, there are two things that can cripple
the server under heavy I/O :
Log files. Configure syslog to use async logs for
whatever dhcp logs end up in. Otherwise, every
discover, offer, request, and ack results in a
wait while the log entry is synced out.
Leases file. Again, every offer or ack is
preceded by writing to the leases file. If the
machine is liable to heavy I/O from other
processes then it may be worth putting the leases
file on it's own storage so dhcpd doesn't find
itself stuck in an I/O queue.
Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
author Gladys Hobson. Novels - poetry - short stories - ideal as
Christmas stocking fillers. Some available as e-books.
More information about the dhcp-users