CPU usage 100% but no process hogging CPU
bruce at cran.org.uk
Sat Oct 27 05:45:53 PDT 2007
Gunther Mayer wrote:
> Hi there,
> I'm having some capacity issues on the FreeBSD 6.2/Core 2 Duo/2GB RAM
> server that I manage. For quite a few days now it constantly shows load
> averages of around 1 and a CPU usage of around 100%. Yet summing up the
> CPU usage of the individual processes running I hardly ever get to more
> than 5%, regardless of how long I watch top.
> A snapshot of my top output looks like this:
> last pid: 96102; load averages: 1.28, 1.15,
> up 22+08:33:16 13:55:03
> 122 processes: 2 running, 119 sleeping, 1 zombie
> CPU states: 67.3% user, 0.0% nice, 32.7% system, 0.0% interrupt, 0.0%
> Mem: 474M Active, 974M Inact, 186M Wired, 68M Cache, 213M Buf, 93M Free
> Swap: 4064M Total, 4064M Free
> PID USERNAME THR PRI NICE SIZE RES STATE TIME WCPU COMMAND
> 635 root 1 122 0 27304K 2644K select 656:38 1.27% syslog-ng
> 844 www 20 20 0 411M 300M kserel 360:13 0.00% java
> 837 user1 3 20 0 29048K 5672K kserel 34:30 0.00% radiusd
> 788 pgsql 1 96 0 13516K 3824K select 10:03 0.00% postgres
> 785 pgsql 1 115 0 120M 7436K select 9:02 0.00% postgres
> 787 pgsql 1 8 0 120M 41112K nanslp 5:15 0.00% postgres
> syslog-ng is quite busy as I use it to capture logs of more than 50
> remote sites. I have lots of slow queries in my postgres logs that I
> think are related to this bottleneck, though unoptimised queries and an
> ever growing amount of data are more likely to take the blame for that.
> High disk I/O in this regard could explain the high system utilisation,
> I found out that I've been bitten by the freebsd-update bug
> which replaced my SMP kernel with a GENERIC one and I'm taking
> corrective action early tomorrow morning, but surely even with just a
> single CPU the load average should never be as high?
> Where are those phantom CPU hogging processes?
By default top doesn't display system (kernel) processes, which can take
up lots of CPU time. To show these, run top with the "-S" flag.
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