Re: PostgreSQL and Xeon MP

On 3/16/06, Sven Geisler <sgeisler(at)aeccom(dot)com> wrote:
> Hi Guillaume,
>
> I had a similar issue last summer. Could you please provide details
> about your XEON MP server and some statistics (context-switches/load/CPU
> usage)?

I forgot the statistics:
CPU load usually from 1 to 4.
CPU usage < 40% for each processor usually and sometimes when the
server completely hangs, it grows to 60%..,

Here is a top output of the server at this time:
15:21:17 up 138 days, 13:25, 1 user, load average: 1.29, 1.25, 1.38
82 processes: 81 sleeping, 1 running, 0 zombie, 0 stopped
CPU states: cpu user nice system irq softirq iowait idle
total 25.7% 0.0% 3.9% 0.0% 0.3% 0.1% 69.7%
cpu00 29.3% 0.0% 4.7% 0.1% 0.5% 0.0% 65.0%
cpu01 20.7% 0.0% 1.9% 0.0% 0.3% 0.0% 76.8%
cpu02 25.5% 0.0% 5.5% 0.0% 0.1% 0.3% 68.2%
cpu03 27.3% 0.0% 3.3% 0.0% 0.1% 0.1% 68.8%
Mem: 3857224k av, 3298580k used, 558644k free, 0k shrd, 105172k buff
2160124k actv, 701304k in_d, 56400k in_c
Swap: 4281272k av, 6488k used, 4274784k free 2839348k cached

We have currently between 3000 and 13000 context switches/s, average
of 5000 I'd say visually.

Here is a top output I had on november 17 when the server completely
hangs (several minutes for each page of the website) and it is typical
of this server behaviour:
17:08:41 up 19 days, 15:16, 1 user, load average: 4.03, 4.26, 4.36
288 processes: 285 sleeping, 3 running, 0 zombie, 0 stopped
CPU states: cpu user nice system irq softirq iowait idle
total 59.0% 0.0% 8.8% 0.2% 0.0% 0.0% 31.9%
cpu00 52.3% 0.0% 13.3% 0.9% 0.0% 0.0% 33.3%
cpu01 65.7% 0.0% 7.6% 0.0% 0.0% 0.0% 26.6%
cpu02 58.0% 0.0% 7.6% 0.0% 0.0% 0.0% 34.2%
cpu03 60.0% 0.0% 6.6% 0.0% 0.0% 0.0% 33.3%
Mem: 3857224k av, 3495880k used, 361344k free, 0k shrd, 92160k buff
2374048k actv, 463576k in_d, 37708k in_c
Swap: 4281272k av, 25412k used, 4255860k free 2173392k cached

As you can see, load is blocked to 4, no iowait and cpu idle of 30%.

Vmstat showed 5000 context switches/s on average so we had no context
switch storm.