RE: VMS process priorities and system processes

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> -----Original Message-----
> From: Albrecht Schlosser [mailto:ajs856@tiscali.de]=20
> Sent: July 15, 2005 6:55 AM
> To: Info-VAX@Mvb.Saic.Com
> Subject: VMS process priorities and system processes
>=20
> Hi,
>=20
> I'm looking for a way to give some application and server=20
> processes different=20
> priorities:
>=20
> highest:  some server processes
> high   :  some other server processes
> medium :  some communication processes
> low    :  some other processes
> lowest :  client processes
>=20
> This would result in a process priority "window" of 5=20
> different priorities.=20
> These priorities should all be higher than normal=20
> (interactive) user priorities,=20
> which are by default 4. Batch priorities are still lower=20
> (from 1 to 3).
>=20
> What I'm concerned about: if I would use priorities 5-9 (or=20
> higher), then some=20
> processes would have higher priorities than some system=20
> processes, as can be=20
> seen here (from a running OpenVMS Itanium 8.2 system):
>=20
> process name          state   username  pri/bpri image
> ------------------------------------------------------------------
> OPCOM                   HIB   SYSTEM      8/ 6   OPCOM
> ERRFMT                  HIB   SYSTEM      8/ 7   ERRFMT
> AUDIT_SERVER            HIB   AUDIT$SERV 10/ 8   AUDIT_SERVER
> TCPIP$INETACP           HIB   INTERNET   10/ 8   TCPIP$INETACP
> IPCACP                  HIB   SYSTEM     10/ 8   IPCACP
> TP_SERVER               HIB   SYSTEM     10/ 8   TPSERV
> QUEUE_MANAGER           HIB   SYSTEM     10/ 8   QMAN$QUEUE_MANAGE
> SECURITY_SERVER         HIB   SYSTEM     10/ 8   SECURITY_SERVER
> JOB_CONTROL             HIB   SYSTEM      9/ 8   JBC$JOB_CONTROL
> TCPIP$FTP_1             LEF   TCPIP$FTP  10/ 8   TCPIP$FTP_SERVER
> LATACP                  HIB   SYSTEM     14/12   LATACP
> LANACP                  HIB   SYSTEM     14/12   LANACP
> SWAPPER                 HIB   SYSTEM     16/16
>=20
> I think that realtime priorities would not be needed, but=20
> what about all these=20
> processes with (base) priorities from 6 to 8, e.g.=20
> TCPIP$INETACP, IPCACP, or=20
> TPSERV. I would prefer to give lower priorities to the=20
> application processes=20
> than to these system processes, but the "window" from 4 to 6=20
> is too small.
>=20
> What do you do WRT process priorities? Raise system process=20
> priorities? What=20
> should be done (or not be done) to keep a stable and=20
> responsive system?
>=20
> Additional background information: Of course, the high=20
> priority server processes=20
> are tested well and stable, but some other processes might=20
> come into a CPU loop=20
> or similar (e.g. once there was a process with a read timeout=20
> of 0 seconds,=20
> which came from a (missing) user input timeout value :-( ).
>=20
> In such cases a system manager should still be able to log in=20
> and suspend/stop=20
> such bad behaving processes. And network activities (many=20
> processes connect via=20
> TCPIP services) should never be blocked by other processes.
>=20
> Any suggestions what to do?
>=20
> Regards
>=20
> Albrecht
>=20

It would appear that you want to ensure some processes of the same
priority do not impact other processese e.g. process runaway stuff.=20

As others have stated, you can get into trouble by purposely mixing
priorities on specific priorities.

As a suggestion, I would suggest you consider using the OpenVMS class
scheduler to do this.

Reference:
Sysman> Help class

http://h71000.www7.hp.com/doc/732FINAL/6048/6048pro_005.html#startsubcom
mand_431
"The class scheduler provides the ability to limit the amount of CPU
time that a system's users receive by placing users in scheduling
classes. Each class is assigned a percentage of the overall system CPU
time. As the system runs, the combined set of users in a class is
limited to the percentage of CPU execution time allocated to their
class.=20

Users might get some additional CPU time if the qualifier /WINDFALL is
enabled for their scheduling class. Enabling the qualifier /WINDFALL
allows the system to give a small amount of CPU time to a scheduling
class when the scheduling class's allotted time has been depleted, but a
free CPU is available."

Regards

Kerry Main
Senior Consultant
HP Services Canada
Voice: 613-592-4660
Fax: 613-591-4477
kerryDOTmainAThpDOTcom
(remove the DOT's and AT)=20

OpenVMS - the secure, multi-site OS that just works.



0
Reply kerry.main (1446) 7/16/2005 8:12:05 PM

See related articles to this posting

Main, Kerry wrote:
> 
>>-----Original Message-----
>>From: Albrecht Schlosser
>>Sent: July 15, 2005 6:55 AM
>>To: Info-VAX@Mvb.Saic.Com
>>Subject: VMS process priorities and system processes
>>
>>Hi,
>>
>>I'm looking for a way to give some application and server 
>>processes different 
>>priorities:
>>
>>highest:  some server processes
>>high   :  some other server processes
>>medium :  some communication processes
>>low    :  some other processes
>>lowest :  client processes
>>
>>This would result in a process priority "window" of 5 
>>different priorities. 

-- snip --

>>Additional background information: Of course, the high 
>>priority server processes 
>>are tested well and stable, but some other processes might 
>>come into a CPU loop 
>>or similar (e.g. once there was a process with a read timeout 
>>of 0 seconds, 
>>which came from a (missing) user input timeout value :-( ).
>>
>>In such cases a system manager should still be able to log in 
>>and suspend/stop 
>>such bad behaving processes. And network activities (many 
>>processes connect via 
>>TCPIP services) should never be blocked by other processes.
>>
>>Any suggestions what to do?
>>
>>Regards
>>
>>Albrecht
>>
> 
> 
> It would appear that you want to ensure some processes of the same
> priority do not impact other processese e.g. process runaway stuff.

There are two goals: First of all the system should operate with reasonable 
performance for all users under normal conditions. The second goal is to 
minimize the impact of misconfigured or bad behaving ("run away") processes that 
could otherwise block critical server processes.

> As others have stated, you can get into trouble by purposely mixing
> priorities on specific priorities.

I don't really understand this sentence.

> As a suggestion, I would suggest you consider using the OpenVMS class
> scheduler to do this.
> 
> Reference:
> Sysman> Help class
> 
> http://h71000.www7.hp.com/doc/732FINAL/6048/6048pro_005.html#startsubcom
> mand_431
> "The class scheduler provides the ability to limit the amount of CPU
> time that a system's users receive by placing users in scheduling
> classes. Each class is assigned a percentage of the overall system CPU
> time. As the system runs, the combined set of users in a class is
> limited to the percentage of CPU execution time allocated to their
> class. 
> 
> Users might get some additional CPU time if the qualifier /WINDFALL is
> enabled for their scheduling class. Enabling the qualifier /WINDFALL
> allows the system to give a small amount of CPU time to a scheduling
> class when the scheduling class's allotted time has been depleted, but a
> free CPU is available."

Interesting suggestion. This didn't come to my mind, though I read about it 
somewhere some time ago. I'll check if it can be of use for us.

> Regards
> 
> Kerry Main
> Senior Consultant
> HP Services Canada
> Voice: 613-592-4660
> Fax: 613-591-4477
> kerryDOTmainAThpDOTcom
> (remove the DOT's and AT) 
> 
> OpenVMS - the secure, multi-site OS that just works.

I second this ;-)

Albrecht
0
Reply ajs856 (48) 7/17/2005 2:06:35 PM
comp.os.vms 20590 articles. 11 followers. Post

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