Re: [HACKERS] Execution time

From: Mattias Kregert <matti(at)algonet(dot)se>
To: Shiby Thomas <sthomas(at)cise(dot)ufl(dot)edu>
Cc: pgsql-hackers(at)postgreSQL(dot)org
Subject: Re: [HACKERS] Execution time
Date: 1998-03-09 12:22:43
Message-ID: 3503DF13.D2EA652@algonet.se
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Shiby Thomas wrote:
>
> The time command will give the elapsed, user CPU and System CPU times.
> How do I interpret it as CPU/IO time ?
>
> Even the -s option of postgres gives those times. Will it be the same as
> using "time postgres" ? Is the System time a reasonable approximation of the
> I/O time and user time that of CPU time ?

I would say they are reasonable approximations, at least for
user==CPU.
Perhaps you need to look at elapsed time too, and from that make some
assumptions about I/O waiting time. I think system time will be lower
if you use SCSI and higher with IDE.
I would count (elapsed time - CPU time) as I/O time.

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