| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Laszlo Nagy <gandalf(at)designaproduct(dot)biz> |
| Cc: | pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: Poor performance on seq scan |
| Date: | 2006-09-12 16:52:06 |
| Message-ID: | 17034.1158079926@sss.pgh.pa.us |
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| Lists: | pgsql-performance |
Laszlo Nagy <gandalf(at)designaproduct(dot)biz> writes:
> Meanwhile, "iostat 5" gives something like this:
> tin tout KB/t tps MB/s KB/t tps MB/s us ni sy in id
> 1 14 128.00 1 0.10 128.00 1 0.10 5 0 94 1 0
> 0 12 123.98 104 12.56 123.74 104 12.56 8 0 90 2 0
> 0 12 125.66 128 15.75 125.26 128 15.68 10 0 85 6 0
> 0 12 124.66 129 15.67 124.39 129 15.64 12 0 85 3 0
> 0 12 117.13 121 13.87 117.95 121 13.96 12 0 84 5 0
> 0 12 104.84 118 12.05 105.84 118 12.19 10 0 87 2 0
Why is that showing 85+ percent *system* CPU time?? I could believe a
lot of idle CPU if the query is I/O bound, or a lot of user time if PG
was being a hog about doing the ~~ comparisons (not too unlikely BTW).
But if the kernel is eating all the CPU, there's something very wrong,
and I don't think it's Postgres' fault.
regards, tom lane
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