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Re: Postgress is taking lot of CPU on our embedded hardware.

From: Jose Ildefonso Camargo Tolosa <ildefonso(dot)camargo(at)gmail(dot)com>
To: Jayashankar K B <Jayashankar(dot)KB(at)lnties(dot)com>
Cc: Claudio Freire <klaussfreire(at)gmail(dot)com>, Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, Andy Colson <andy(at)squeakycode(dot)net>, "pgsql-performance(at)postgresql(dot)org" <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Postgress is taking lot of CPU on our embedded hardware.
Date: 2012-01-29 14:46:35
Message-ID: CAETJ_S-7qRHUS_Yf7jvS_OyppxpVE0BX9uDr5OPu2y-kXZAcpQ@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-performance
Greetings,

On Sat, Jan 28, 2012 at 12:51 PM, Jayashankar K B
<Jayashankar(dot)KB(at)lnties(dot)com> wrote:
> Hi,
>
> I downloaded the source code and cross compiled it into a relocatable package and copied it to the device.
> LTIB was the cross-compile tool chain that was used. Controller is  coldfire MCF54418 CPU.
> Here is the configure options I used.

Ok, no floating point, and just ~250MHz... small.  Anyway, lets not
talk about hardware options, because you already have it.

About kernel, I'm not sure if on this arch you have the option, but
did you enable "PREEMPT" kernel config option? (on menuconfig:
"Preemptible Kernel (Low-Latency Desktop)")....  Or, is that a RT
kernel?

With such a small CPU, almost any DB engine you put there will be
CPU-hungry, but if your CPU usage is under 95%, you know you still
have some CPU to spare, on the other hand, if you are 100% CPU, you
have to evaluate required response time, and set priorities
accordingly.. However, I have found that, even with processes with
nice level 19 using 100% CPU, other nice level 0 processes will
slow-down unless I set PREEMPT option to on kernel compile options
(other issue are IO wait times, at least on my application that uses
CF can get quite high).

Sincerely,

Ildefonso Camargo

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