Re: High load average in 64-core server , no I/O wait and CPU is idle

[Andy Colson <andy@xxxxxxxxxxxxxxx>]

On 05/24/2012 12:26 AM, Rajesh Kumar. Mallah wrote:
> ----- "Claudio Freire"<klaussfreire@xxxxxxxxx>  wrote:
>
> | From: "Claudio Freire"<klaussfreire@xxxxxxxxx>
> | To: "Rajesh Kumar. Mallah"<mallah@xxxxxxxxxxxxxx>
> | Cc: pgsql-performance@xxxxxxxxxxxxxx
> | Sent: Thursday, May 24, 2012 9:23:43 AM
> | Subject: Re:  High load average in 64-core server , no I/O wait and CPU is idle
> |
> | On Thu, May 24, 2012 at 12:39 AM, Rajesh Kumar. Mallah
> |<mallah@xxxxxxxxxxxxxx>  wrote:
> |>  The problem is that  sometimes there are spikes of load avg which
> |>  jumps to>  50 very rapidly ( ie from 0.5 to 50  within 10 secs) and
> |>  it remains there for sometime and slowly reduces to normal value.
> |>
> |>  During such times of high load average we observe that there is no
> | IO wait
> |>  in system and even CPU is 50% idle. In any case the IO Wait always
> | remains<  1.0 % and
> |>  is mostly 0. Hence the load is not due to high I/O wait which was
> | generally
> |>  the case with our previous hardware.
> |
> | Do you experience decreased query performance?
>
>
> Yes we do experience substantial application performance degradations.

Maybe you are hitting some locks?   If its not IO and not CPU then maybe something is getting locked and queries are piling up.

-Andy

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