PDQ on a single processor system

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JÃ¶rg RÃ1/4schenschmidt - 28 Oct 2006 09:19 GMT

Hi,

can sombody tell me if I can benefit from PDQ on single processor system ?

According Informix performance guide, multiple treads are started when
when PDQ is used, but can i benefit from this wif one physical processor
is available only ? I am afraid the extra work to manage the multiple
threads will be bad for the overall Informix performance on a single
processor system ?

Is it better to set PDQ_MAXPRIORITY to 0 in case a single processor
system is used ?

Any experience ?

Regards ...

Joerg

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Neil Truby - 28 Oct 2006 10:06 GMT

Possibly it depends upon your hardware. Multi-cored and multi-threaded
processors possibly would benefit from multiple cpu vps, but wih an elderly,
single-core, single processor your concern that you may lose more on the
swings of conext switching than you gain on the roundabouts of Informix
parallel processing may well be founded.

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> Hi,
>
[quoted text clipped - 14 lines]
>
> Joerg

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scottishpoet - 28 Oct 2006 10:53 GMT

I think if you have multiple disks then more then the disks can be
accessed in parallel rather than serially. Its then a balance point of
how busy the ready Q becomes to process the data returned from the
disks 2 disks may be OK, 10 may swamp the the ready Q

> Hi,
>
[quoted text clipped - 14 lines]
>
> Joerg

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Andreas Legner - 28 Oct 2006 22:50 GMT

Don't underestimate the memory restrictions when not using PDQ_PRIORITY.

Still when using version 10.00 or later 9.40s, DS_NONPDQ_QUERY_MEM can also help out here.

Regards,
Andreas

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