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Disable CPU

 
FOX MULDER_2
Frequent Advisor

Disable CPU

Hi,
Can anyone please tell me how to disable one CPU from VMS (if there is any way) or from
>>> prompt without removing the hardware physically(assuming there are 2 CPU are present and both are in good health).

So that when given
$ sh cpu
it should display
PRIMARY CPU = 00
Active CPUs: 00
Configured CPUs: 00

Thanks
11 REPLIES
Andy Bustamante
Honored Contributor

Re: Disable CPU


$ stop/cpu 1

will disable the second CPU on a two CPU system. The show CPU will list both, but the second will not be active. You can't stop the primary CPU, CPU 0.

Andy
If you don't have time to do it right, when will you have time to do it over? Reach me at first_name + "." + last_name at sysmanager net
Dean McGorrill
Valued Contributor

Re: Disable CPU

You can in sysgen set MULTIPROCESSING = 0.
that will always then just use 1 cpu. curious what you are trying to accomplish.
I stop a processor if I think its buggy
and will crash the system, we have another
thread on that. Also we used to stop processors when debugging smp code that
was corrupting our datastructures. Dean
FOX MULDER_2
Frequent Advisor

Re: Disable CPU

Thanks for the prompt replies.
However,please tell me how to enable multiprocessing as due to its disablity CPU usage is 100% all times.
$ sh cpu
a AlphaServer 2100 4/275
Multiprocessing is DISABLED. Uniprocessing synchronization image loaded.
Minimum multiprocessing revision levels: CPU = 1

PRIMARY CPU = 00
Active CPUs: 00
Configured CPUs: 00
OBERON$:> mcr sysgen
SYSGEN> SH MULTI
Parameter Name Current Default Min. Max. Unit Dynamic
-------------- ------- ------- ------- ------- ---- -------
MULTIPROCESSING 3 3 0 4 Coded-valu
SYSGEN>


Thanks
Richard Whalen
Honored Contributor

Re: Disable CPU

Since your current value for MULTIPROCESSING is 3 (the default), you must only have 1 processor as the multiprocessing software is only loaded if there are multiple processors present when the value is 3.

SYSGEN> HELP SYS_P MULTIPROCESSING

Sys_Parameters

MULTIPROCESSING

MULTIPROCESSING controls the loading of the system
synchronization image.

Specify one of the following values:

Value Description

0 Load the uniprocessing synchronization image
SYSTEM_SYNCHRONIZATION_UNI.EXE.

1 If the CPU type is capable of SMP and two or
more CPUs are present on the system, load the
full-checking multiprocessing synchronization
image SYSTEM_SYNCHRONIZATION.EXE. Otherwise,
load the uniprocessing synchronization image
SYSTEM_SYNCHRONIZATION_UNI.EXE.

2 Always load the full-checking version
SYSTEM_SYNCHRONIZATION.EXE, regardless of system
configuration or CPU availability.

3 If the CPU type is capable of SMP and two or more
CPUs are present on the system, load the optimized
streamlined multiprocessing image:

o On VAX systems, this image is
SYSTEM_SYNCHRONIZATION_SPC.EXE.

o On Alpha and I64 systems, this image is
SYSTEM_SYNCHRONIZATION_MIN.EXE.

Otherwise, load the uniprocessing synchronization image
SYSTEM_SYNCHRONIZATION_UNI.EXE. The default value is 3.

4 Always load the streamlined multiprocessing image
SYSTEM_SYNCHRONIZATION_MIN.EXE, regardless of system
configuration or CPU availability.

Setting the SYSTEM_CHECK parameter to 1 has the effect of setting
MULTIPROCESSING to 2.

Andy Bustamante
Honored Contributor

Re: Disable CPU

It looks like you only have 1 CPU installed on this system. If there is another, it's probably having a bad hardware day.

You'll need to purchase another CPU module and an license. For a system this old, I believe it would make more sense to upgrade to a more recent model. You can have up to 4 CPUs installed.

Before deciding that you need to upgrade, you should evaluate the system in place now.

Andy
If you don't have time to do it right, when will you have time to do it over? Reach me at first_name + "." + last_name at sysmanager net
Thomas Ritter
Respected Contributor

Re: Disable CPU

We have a dual processor ES40 which only has a license for one cpu. We disable the 2nd cpu using the sysgen parameter SMP_CPUS
Our value is

SMP_CPUS = 0 !Disable SMP processing


From sysgen help
SMP_CPUS

SMP_CPUS identifies which secondary processors, if available,
are to be booted into the multiprocessing system at boot time.
SMP_CPUS is a 32-bit mask; if the value of a bit in the mask is
1, the processor with the corresponding CPU ID is booted into
the multiprocessing system (if it is available). For example, if
you want to boot only the CPUs with CPU IDs 0 and 1, specify the
value 3 (both bits are on).

The default value of SMP_CPUS, -1, boots all available CPUs into
the multiprocessing system.
Volker Halle
Honored Contributor

Re: Disable CPU

Fox,

please explain: what is your problem ???

In your 2nd reply, you're talking about 100% CPU utilization. Is that your problem ?

Volker.
FOX MULDER_2
Frequent Advisor

Re: Disable CPU

Hi,

The concern for CPU usage is there,its taking up 100% all times.
Few days back there was an activity on the server for after which performance issue was there.
Some how I was hoping one CPU is not responding or disabled somehow.

That is the concern.
I have checked on the sysgen parameters and found that when I set the system_check to 1, and on executing sh cpu that multiprocessing is enabled.

Can anyone please tell me on VMS with 1 CPU, is multiprocessing really taking place ?

Thanks
Volker Halle
Honored Contributor

Re: Disable CPU

Fox,

multiprocessing is NOT taking place, if you only have 1 CPU. You can load the multiprocessing code, but there is only 1 CPU.

So you problem is, that the one and only CPU is always 100% busy...

Start with MONI MODE, MONI SYSTEM, MONI PROC/TOPCPU

- in which mode is the CPU most of the time ?
- any process using unusual amounts of CPU time ?

Volker.
Volker Halle
Honored Contributor

Re: Disable CPU

Fox,

an AlphaServer 2100 could have up to 4 CPUs installed. How many do you physically have installed ?

$ ANAL/SYS
SDA> CLUE CONFIG
SDA> EXIT

would tell OpenVMS's view of the CPUs.

>>> SHOW CONFIG

will tell the console's view.

Volker.
Robert Brooks_1
Honored Contributor

Re: Disable CPU

I'm not sure why you enabled SYSTEM_CHECK, but I can guarantee that your CPU time will go way up; the execlets that get loaded when SYSTEM_CHECK is on are really only useful for debugging by VMS Engineering because they contain a lot more consistency checking at various places, and there is a high CPU cost for that.

-- Rob