Experimental Physics and
Industrial Control System

1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 <2021> 2022 2023 2024	Index	1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 <2021> 2022 2023 2024
<== Date ==>		<== Thread ==>

Subject:	Re: Changing EPICS general Purpose Thread's Priorities
From:	"Kim, Kukhee via Tech-talk" <tech-talk at aps.anl.gov>
To:	"tech-talk at aps.anl.gov" <tech-talk at aps.anl.gov>, "jun-ichi.odagiri at kek.jp" <jun-ichi.odagiri at kek.jp>
Date:	Fri, 26 Mar 2021 15:59:52 +0000

Dear Odagiri san,

Long time no see, I am glad to see your message 🙂

> Can I change the priority of "CAS-TCP" thread and "scan-10"
> thread so that the former is given a higher priority than
> that of the latter without modifying any source files in
> base?

It is possible to modify thread priority after the launching process, even possible to modify the scheduling policy (ex, SCHED_OTERH to SCHED_FIFO, to the real-time priority).

Please, check up the followings:

I am using linuxRT - preempted rt patch for this example.

uname -a

Linux cpu-b084-pm01 4.14.139-rt66 #1 SMP PREEMPT RT Mon Sep 30 14:33:17 PDT 2019 x86_64 GNU/Linux

We can check up process id, parent id, thread id, rt-priority, start time, running time, and thread name with the following command.

ps -Leo pid,ppid,tid,rtprio,stime,time,comm

21994 21993 22010 - Mar23 00:00:00 tpg
21994 21993 22011 - Mar23 00:00:00 tpg

21994 21993 22209 59 Mar23 00:00:00 timerQueue

21994 21993 22210 59 Mar23 00:00:00 timerQueue

21994 21993 22212 - Mar23 00:00:00 tpg

21994 21993 22215 - Mar23 00:00:00 tpg

21994 21993 22216 10 Mar23 00:00:00 taskwd

21994 21993 22217 69 Mar23 00:00:00 timerQueue

21994 21993 22218 58 Mar23 00:01:39 cbLow

21994 21993 22219 63 Mar23 00:00:00 cbMedium

21994 21993 22220 70 Mar23 00:00:00 cbHigh

21994 21993 22221 50 Mar23 00:00:00 dbCaLink

21994 21993 22222 98 Mar23 00:12:35 tpgIrqPollingTa

21994 21993 22223 89 Mar23 00:04:02 tpgSoftPollingT

21994 21993 22224 50 Mar23 00:02:59 tpgBsaPollingTa

21994 21993 22225 10 Mar23 00:01:13 tpgRateMeasureP

21994 21993 22226 10 Mar23 00:02:07 tpgDiagnosticsT

21994 21993 22227 50 Mar23 00:02:40 bsaDrvPoll

21994 21993 22228 57 Mar23 00:00:13 timerQueue

21994 21993 22229 66 Mar23 00:00:00 scanOnce

21994 21993 22230 59 Mar23 00:00:00 scan-10

21994 21993 22231 60 Mar23 00:00:00 scan-5

21994 21993 22232 61 Mar23 00:00:01 scan-2

21994 21993 22233 62 Mar23 00:00:07 scan-1

21994 21993 22234 63 Mar23 00:00:14 scan-0.5

21994 21993 22235 64 Mar23 00:00:09 scan-0.2

21994 21993 22236 65 Mar23 00:00:18 scan-0.1

21994 21993 22237 56 Mar23 00:00:00 asCaTask

21994 21993 22238 16 Mar23 00:00:00 CAS-TCP

21994 21993 22239 12 Mar23 00:00:54 CAS-UDP

21994 21993 22240 14 Mar23 00:00:00 CAS-beacon

21994 21993 22241 51 Mar23 00:00:00 CAC-event

21994 21993 22242 10 Mar23 00:00:00 logRestart

21994 21993 22243 10 Mar23 00:00:00 caPutLog

21994 21993 22244 20 Mar23 00:00:24 save_restore

21994 21993 22245 10 Mar23 00:00:00 ipToAsciiProxy

21994 21993 22246 22 Mar23 00:01:42 timerQueue

21994 21993 22247 24 Mar23 00:00:27 CAC-UDP

21994 21993 22250 22 Mar23 00:00:04 CAC-event

21994 21993 22778 18 08:36 00:00:00 CAS-event

21994 21993 22779 20 08:36 00:00:00 CAS-client

22756 6877 22756 - 08:28 00:00:00 dropbear

The 3rd column is thread id, and the 4th column is a priority. The symbol "-" means no rt-priority for the thread, SCHED_OTHER.

The thread "scan-10" has thread id 22230 and rt-priority 59.

The thread "CAS-TCP" has thread id 22238 and rt-priority 16.

If we want to escalate the rt-priority for those threads, we can do the followings:

# Escalate rt-priority of scan-10 to 60

chrt -f -p 60 22230
pid 22230's current scheduling policy: SCHED_FIFO

pid 22230's current scheduling priority: 59

pid 22230's new scheduling policy: SCHED_FIFO
pid 22230's new scheduling priority: 6

# Escalate rt-priority of CAS-TCP to 20

chrt -f -p 20 22238
pid 22238's current scheduling policy: SCHED_FIFO

pid 22238's current scheduling priority: 16

pid 22238's new scheduling policy: SCHED_FIFO

pid 22238's new scheduling priority: 20

Then, you can see the priorities of those two threads were escalated.

21994 21993 22229 66 Mar23 00:00:00 scanOnce

21994 21993 22230 60 Mar23 00:00:00 scan-10 <========== 59 to 60

21994 21993 22231 60 Mar23 00:00:00 scan-5

21994 21993 22232 61 Mar23 00:00:01 scan-2

21994 21993 22233 62 Mar23 00:00:07 scan-1

21994 21993 22234 63 Mar23 00:00:14 scan-0.5

21994 21993 22235 64 Mar23 00:00:09 scan-0.2

21994 21993 22236 65 Mar23 00:00:18 scan-0.1

21994 21993 22237 56 Mar23 00:00:00 asCaTask

21994 21993 22238 20 Mar23 00:00:00 CAS-TCP <========= 16 to 20

21994 21993 22239 12 Mar23 00:00:54 CAS-UDP

21994 21993 22240 14 Mar23 00:00:00 CAS-beacon

I think the help message of the "chrt" will be helpful.

chrt --help
BusyBox v1.31.0 (2019-09-30 13:30:59 PDT) multi-call binary.

Usage: chrt -m | -p [PRIO] PID | [-rfobi] PRIO PROG [ARGS]

Change scheduling priority and class for a process

-m Show min/max priorities

-p Operate on PID

-r Set SCHED_RR class

-f Set SCHED_FIFO class

-o Set SCHED_OTHER class

-b Set SCHED_BATCH class

-i Set SCHED_IDLE class

Thank you.

Best regards,

Kukhee

From: Tech-talk <tech-talk-bounces at aps.anl.gov> on behalf of jun-ichi.odagiri--- via Tech-talk <tech-talk at aps.anl.gov>
Sent: Friday, March 26, 2021 12:09 AM
To: tech-talk at aps.anl.gov <tech-talk at aps.anl.gov>
Subject: Re: Changing EPICS general Purpose Thread's Priorities

Dear Han san,

Thank you for sending me the information.
I took a look at the site you have let me know.
But, I may be dense, I could not get the point.
It seems like that the information on the site is related
to Multi-Core Linux.

To be more concrete, I tell you what I have in my mind as
follows.

1. A Single-Core CPU is running Linux.
2. Only one IOC program is running on the Linux.
3. The IOC program is multi-threaded, as every one knows.

Here is my question.

Can I change the priority of "CAS-TCP" thread and "scan-10"
thread so that the former is given a higher priority than
that of the latter without modifying any source files in
base?

Does the site you guided me to answer the question?

Thanks a lot again in advance.

Best regards,

J.Odagiri at KEK.

----- Original Message -----
> Jun-ichi Odagiri san,
>
> This may be what you are looking for.
>
> https://github.com/epics-modules/MCoreUtils
>
> Best,
> Han
>
>
> On Thu, Mar 25, 2021 at 4:55 PM jun-ichi.odagiri--- via Tech-talk
> <tech-talk at aps.anl.gov> wrote:
> >
> > Hi, all
> >
> > Do we have a way to change the priorities of the EPICS
> > general purpose threads dynamically on the iocsh？
> >
> > Thanks a lot in advance.
> >
> > Jun-ichi Odagiri(KEK)
> >
> >
> >
>

Replies:: Re: Changing EPICS general Purpose Thread's Priorities jun-ichi.odagiri--- via Tech-talk

References:: MRF kernel module, failed to map BARS GAGET Alexis via Tech-talk; Re: MRF kernel module, failed to map BARS Michael Davidsaver via Tech-talk; RE: MRF kernel module, failed to map BARS GAGET Alexis via Tech-talk; Changing EPICS general Purpose Thread's Priorities jun-ichi.odagiri--- via Tech-talk; Re: Changing EPICS general Purpose Thread's Priorities Jeong Han Lee via Tech-talk; Re: Changing EPICS general Purpose Thread's Priorities jun-ichi.odagiri--- via Tech-talk

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ANJ, 30 Mar 2021

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Experimental Physics and Industrial Control System

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