Informix performance on 1, 2 or 4 processors??
Kerry Lyall
Please Help! I am getting conflicting answers.
HP and Informix say performance on 2 processors (1 for OS & 1 for DB)
is fine.
A user I know says they heard at an Informix Performance Seminar at
last summers World Wide Conference that performance on 2 processors is
a "real dog"!! This user says I should be on a 1 or 4 processor but
NOT 2 processors !!??
Comments, please.
Thanx in adv
Kerry
kal...@cal-gold.com
Irwin Goldstein
Kerry Lyall <kal...@concentric.net> wrote in article
<5im68n$s...@chronicle.concentric.net>...
> Please Help! I am getting conflicting answers.
>
> HP and Informix say performance on 2 processors (1 for OS & 1 for DB)
> is fine.
>
> A user I know says they heard at an Informix Performance Seminar at
> last summers World Wide Conference that performance on 2 processors is
> a "real dog"!! This user says I should be on a 1 or 4 processor but
> NOT 2 processors !!??
Most of the tribal wisdom I've heard suggests that when running on a 2
processor machne, configure Informix as if you had only a single processor.
(NUMCPUVPS=1, MULTIPROCESSOR=0 in the onconfig file.) The overhead
associated with the multi-cpu coordination is not worth it when all you are
gaining is one additional CPU. Configured this way, Informix should
perform at least as well on a 2 CPU box as on a one CPU box. The second
CPU will in fact help speed things up some, but intra-query parallelism
(other than possibly parallel scans) will not be utilized.
--
Irwin Goldstein
Objective Software Systems, Inc.
http://www.objectsoft.com
SaTriGuy
This is true. The MULTIPROCESSOR tag does not affect locking of memory
and/or data. What it really does is to place the vp in a spin loop when a
resource is locked with the idea that the "other" physical processor will
give up the lock quickly. If MULTIPROCESSOR is turned off, then the vp
will go to sleep and/or issue a poll/select if the lock is "raised".
Also, by setting up two cpuvps on a two processor system will enable you
to have two kaiothreads.
Madison Pruet
Ron M. Flannery
At 12:54 AM 4/13/97 GMT, Irwin Goldstein wrote:
}Kerry Lyall <kal...@concentric.net> wrote in article
}<5im68n$s...@chronicle.concentric.net>...
}> Please Help! I am getting conflicting answers.
}>
}> HP and Informix say performance on 2 processors (1 for OS & 1 for DB)
}> is fine.
}>
}> A user I know says they heard at an Informix Performance Seminar at
}> last summers World Wide Conference that performance on 2 processors is
}> a "real dog"!! This user says I should be on a 1 or 4 processor but
}> NOT 2 processors !!??
}
}Most of the tribal wisdom I've heard suggests that when running on a 2
}processor machne, configure Informix as if you had only a single processor.
} (NUMCPUVPS=1, MULTIPROCESSOR=0 in the onconfig file.) The overhead
}associated with the multi-cpu coordination is not worth it when all you are
}gaining is one additional CPU. Configured this way, Informix should
}perform at least as well on a 2 CPU box as on a one CPU box. The second
}CPU will in fact help speed things up some, but intra-query parallelism
}(other than possibly parallel scans) will not be utilized.
Generally speaking, you would also want to set SINGLE_CPU_VP=1 in this case
(when NUMCPUVPS=1). If you do go back to >1 for NUMCPUVPS, you'll get
initialization errors so you'll need to set SINGLE_CPU_VP back to 0.
In fact, you should *always* be sure to check the values of these three
parameters (NUMCPUVPS, MULTIPROCESSOR, and SINGLE_CPU_VPS) on a single
processor box as they can really help or hinder performance.
Ron Flannery |
rfla...@zenacomp.com | President,
ZenaComp Incorporated | Michigan Informix User Group
http://www.zenacomp.com | http://www.zenacomp.com/miug.html
Clem Akins
>Please Help! I am getting conflicting answers.
Welcome to the wonderful world of system tuning. Get used to it. :)
>HP and Informix say performance on 2 processors (1 for OS & 1 for DB)
>is fine.
It is very fine, thank you, for customers whose needs are met by that
configuration. That may be you! Define "fine" and we'll see what it
takes to attain that specification.
When I used to run hot rods, we had a saying:
"Speed costs money. How fast do you want to go?"
>A user I know says they heard at an Informix Performance Seminar at
>last summers World Wide Conference that performance on 2 processors is
>a "real dog"!! This user says I should be on a 1 or 4 processor but
>NOT 2 processors !!??
Believe half of what you read, and none of what you hear. (So I hear.)
Here are some things to read:
"Informix-OnLine Performance Tuning" by Liz Suto
See especially page 93 (in the first edition)
"Informix-OnLine Dynamic Server Administrator's Guide version 7.1"
Chapter 10, page 10-19 "CPU Virtual Processors"
and Chapter 38, page 38-59 "SINGLE_CPU_VP"
"Informix-OnLine Performance Tuning Guide"
Heck, just read the whole thing
In summary:
Performance is excellent if your needs are being met. It is NOT! measured
by how many CPUs you have. Unless your needs are exactly the same as
another's,
be wary of comparisons between your benchmarks. And (I just gotta say it)
RTFM.
Happy computing,
______________________________________________________
Clem Akins (aka cl...@informix.com)
Informix Software, Inc (Standard disclaimers apply)
International Technical Support
Last seen: In KL, near the World's Tallest Building
Paulo N
In article <5im68n$s...@chronicle.concentric.net>, kal...@concentric.netç
says...
>
>Please Help! I am getting conflicting answers.
>
>is fine.
>
>last summers World Wide Conference that performance on 2 processors is
>a "real dog"!! This user says I should be on a 1 or 4 processor but
>NOT 2 processors !!??
>
there is no unique answer for the number of CPUs VPs in a system. My experience
tells that depending of the tasks to perform you may add or nor CPU vps. The
manual says to configure the system with 1 cpu less than the hardware but in
ALPHA machines you may add CPUs until processors idle time go down to 20% (in
peek usage time).
- I've system with 3 x ALPHA 5/300 CPUs and a total of 12 CPUs VPs (in
different Informix engines).
Best regards