Re: PostgreSQL and Xeon MP

On 3/16/06, Sven Geisler <sgeisler@aeccom.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.