Run a Cygwin process with "higher" scheduler priority

Run a Cygwin process with "higher" scheduler priority

[Cedric Blancher]

Good evening!

How can we set the scheduler priority for a Cygwin process to "higher"
than normal on start?

Basically we want a Cygwin compatible script version of the Windows
task manager feature Name/PID--->Details--->Set priority--->Higher

Ced
-- 
Cedric Blancher <cedric.blancher@gmail.com>
[https://plus.google.com/u/0/+CedricBlancher/]
Institute Pasteur

Re: Run a Cygwin process with "higher" scheduler priority

[Brian Inglis]

On 2023-08-11 09:44, Cedric Blancher via Cygwin wrote:
> How can we set the scheduler priority for a Cygwin process to "higher"
> than normal on start?
> 
> Basically we want a Cygwin compatible script version of the Windows
> task manager feature Name/PID--->Details--->Set priority--->Higher

Pretend the system is BSD or Linux and web search e.g. SO for that capability, 
facility, or feature, then check Cygwin with Search Packages or:

$ cygcheck -p usr/bin/nice
Found 6 matches for usr/bin/nice
coreutils-debuginfo-8.26-2 - coreutils-debuginfo: Debug info for coreutils
...
coreutils-9.0-1 - coreutils: GNU core utilities (includes fileutils, sh-utils 
and textutils)
$ cygcheck -p usr/bin/renice
Found 6 matches for usr/bin/renice
util-linux-debuginfo-2.32.1-1 - util-linux-debuginfo: Debug info for util-linux
util-linux-debuginfo-2.33.1-1 - util-linux-debuginfo: Debug info for util-linux
util-linux-debuginfo-2.33.1-2 - util-linux-debuginfo: Debug info for util-linux
util-linux-2.32.1-1 - util-linux: Collection of basic system utilities
util-linux-2.33.1-1 - util-linux: Collection of basic system utilities
util-linux-2.33.1-2 - util-linux: Collection of basic system utilities
$ cygcheck -p usr/bin/chrt
Found 2 matches for usr/bin/chrt
util-linux-debuginfo-2.33.1-2 - util-linux-debuginfo: Debug info for util-linux
util-linux-2.33.1-2 - util-linux: Collection of basic system utilities
$ cygcheck -p usr/bin/taskset
Found 2 matches for usr/bin/taskset
util-linux-debuginfo-2.33.1-2 - util-linux-debuginfo: Debug info for util-linux
util-linux-2.33.1-2 - util-linux: Collection of basic system utilities

so you may need to install util-linux (coreutils is already installed as a base 
package for Cygwin) then:

	$ man nice renice taskset chrt

You may need to run these from an elevated admin shell for other user ids, 
unowned processes, or higher (negative) priority.

It has been years since I tried these so can no longer remember if -20 
corresponds to Windows "RealTime" or if you need to use PowerShell to set that e.g.

	$proc	= Get-Process -ProcessName "..."
	$proc.PriorityClass	= "RealTime"

and that needs to be done from an elevated admin (Power)Shell.

Of course, never set that on any system except on a very idle, very I/O bound, 
well tested process, such as ntpd, that needs stably fast interrupt service and 
non-preemptible cpu access for ms every few seconds, preferably on a single or 
few cpus to which affinity is set.

-- 
Take care. Thanks, Brian Inglis              Calgary, Alberta, Canada

La perfection est atteinte                   Perfection is achieved
non pas lorsqu'il n'y a plus rien à ajouter  not when there is no more to add
mais lorsqu'il n'y a plus rien à retirer     but when there is no more to cut
                                 -- Antoine de Saint-Exupéry

Re: Run a Cygwin process with "higher" scheduler priority

[Cedric Blancher]

On Fri, 11 Aug 2023 at 19:14, Brian Inglis <Brian.Inglis@shaw.ca> wrote:
>
> On 2023-08-11 09:44, Cedric Blancher via Cygwin wrote:
> > How can we set the scheduler priority for a Cygwin process to "higher"
> > than normal on start?
> >
> > Basically we want a Cygwin compatible script version of the Windows
> > task manager feature Name/PID--->Details--->Set priority--->Higher
>
> Pretend the system is BSD or Linux and web search e.g. SO for that capability,
> facility, or feature, then check Cygwin with Search Packages or:
>
> $ cygcheck -p usr/bin/nice
> Found 6 matches for usr/bin/nice

I know about nice and renice, but I don't see whether it is working or not.

> coreutils-debuginfo-8.26-2 - coreutils-debuginfo: Debug info for coreutils
> ...
> coreutils-9.0-1 - coreutils: GNU core utilities (includes fileutils, sh-utils
> and textutils)
> $ cygcheck -p usr/bin/renice
> Found 6 matches for usr/bin/renice
> util-linux-debuginfo-2.32.1-1 - util-linux-debuginfo: Debug info for util-linux
> util-linux-debuginfo-2.33.1-1 - util-linux-debuginfo: Debug info for util-linux
> util-linux-debuginfo-2.33.1-2 - util-linux-debuginfo: Debug info for util-linux
> util-linux-2.32.1-1 - util-linux: Collection of basic system utilities
> util-linux-2.33.1-1 - util-linux: Collection of basic system utilities
> util-linux-2.33.1-2 - util-linux: Collection of basic system utilities
> $ cygcheck -p usr/bin/chrt
> Found 2 matches for usr/bin/chrt
> util-linux-debuginfo-2.33.1-2 - util-linux-debuginfo: Debug info for util-linux
> util-linux-2.33.1-2 - util-linux: Collection of basic system utilities
> $ cygcheck -p usr/bin/taskset
> Found 2 matches for usr/bin/taskset
> util-linux-debuginfo-2.33.1-2 - util-linux-debuginfo: Debug info for util-linux
> util-linux-2.33.1-2 - util-linux: Collection of basic system utilities
>
> so you may need to install util-linux (coreutils is already installed as a base
> package for Cygwin) then:
>
>         $ man nice renice taskset chrt

chrt does not work, the syscalls for realtime seem to be not implemented.

>
> You may need to run these from an elevated admin shell for other user ids,
> unowned processes, or higher (negative) priority.
>
> It has been years since I tried these so can no longer remember if -20
> corresponds to Windows "RealTime" or if you need to use PowerShell to set that e.g.
>
>         $proc   = Get-Process -ProcessName "..."
>         $proc.PriorityClass     = "RealTime"
>
> and that needs to be done from an elevated admin (Power)Shell.
>
> Of course, never set that on any system except on a very idle, very I/O bound,
> well tested process, such as ntpd, that needs stably fast interrupt service and
> non-preemptible cpu access for ms every few seconds, preferably on a single or
> few cpus to which affinity is set.

Is there anything in /proc which can tell me the current *Windows*
scheduler priority level? Or a command line tool?

Ced

Re: Run a Cygwin process with "higher" scheduler priority

[Eliot Moss]

On 10/14/2023 7:39 AM, Cedric Blancher via Cygwin wrote:
> On Fri, 11 Aug 2023 at 19:14, Brian Inglis <Brian.Inglis@shaw.ca> wrote:
>>
>> On 2023-08-11 09:44, Cedric Blancher via Cygwin wrote:
>>> How can we set the scheduler priority for a Cygwin process to "higher"
>>> than normal on start?
>>>
>>> Basically we want a Cygwin compatible script version of the Windows
>>> task manager feature Name/PID--->Details--->Set priority--->Higher
>>
>> Pretend the system is BSD or Linux and web search e.g. SO for that capability,
>> facility, or feature, then check Cygwin with Search Packages or:
>>
>> $ cygcheck -p usr/bin/nice
>> Found 6 matches for usr/bin/nice
> 
> I know about nice and renice, but I don't see whether it is working or not.
> 
>> coreutils-debuginfo-8.26-2 - coreutils-debuginfo: Debug info for coreutils
>> ...
>> coreutils-9.0-1 - coreutils: GNU core utilities (includes fileutils, sh-utils
>> and textutils)
>> $ cygcheck -p usr/bin/renice
>> Found 6 matches for usr/bin/renice
>> util-linux-debuginfo-2.32.1-1 - util-linux-debuginfo: Debug info for util-linux
>> util-linux-debuginfo-2.33.1-1 - util-linux-debuginfo: Debug info for util-linux
>> util-linux-debuginfo-2.33.1-2 - util-linux-debuginfo: Debug info for util-linux
>> util-linux-2.32.1-1 - util-linux: Collection of basic system utilities
>> util-linux-2.33.1-1 - util-linux: Collection of basic system utilities
>> util-linux-2.33.1-2 - util-linux: Collection of basic system utilities
>> $ cygcheck -p usr/bin/chrt
>> Found 2 matches for usr/bin/chrt
>> util-linux-debuginfo-2.33.1-2 - util-linux-debuginfo: Debug info for util-linux
>> util-linux-2.33.1-2 - util-linux: Collection of basic system utilities
>> $ cygcheck -p usr/bin/taskset
>> Found 2 matches for usr/bin/taskset
>> util-linux-debuginfo-2.33.1-2 - util-linux-debuginfo: Debug info for util-linux
>> util-linux-2.33.1-2 - util-linux: Collection of basic system utilities
>>
>> so you may need to install util-linux (coreutils is already installed as a base
>> package for Cygwin) then:
>>
>>          $ man nice renice taskset chrt
> 
> chrt does not work, the syscalls for realtime seem to be not implemented.
> 
>>
>> You may need to run these from an elevated admin shell for other user ids,
>> unowned processes, or higher (negative) priority.
>>
>> It has been years since I tried these so can no longer remember if -20
>> corresponds to Windows "RealTime" or if you need to use PowerShell to set that e.g.
>>
>>          $proc   = Get-Process -ProcessName "..."
>>          $proc.PriorityClass     = "RealTime"
>>
>> and that needs to be done from an elevated admin (Power)Shell.
>>
>> Of course, never set that on any system except on a very idle, very I/O bound,
>> well tested process, such as ntpd, that needs stably fast interrupt service and
>> non-preemptible cpu access for ms every few seconds, preferably on a single or
>> few cpus to which affinity is set.
> 
> Is there anything in /proc which can tell me the current *Windows*
> scheduler priority level? Or a command line tool?

I recall getting taskset going in util-linux a while back, but I don't
recall working on priority related things.  You could look into the
cygwin source code to see how Windows priorities relate to the priority
values in Cygwin.  Then you may be able just to use /proc/[pid]/stat
read out what you want.

Best - EM

Re: Run a Cygwin process with "higher" scheduler priority

[Mark Geisert]

Cedric Blancher via Cygwin wrote:
> On Fri, 11 Aug 2023 at 19:14, Brian Inglis <Brian.Inglis@shaw.ca> wrote:
>>
>> On 2023-08-11 09:44, Cedric Blancher via Cygwin wrote:
>>> How can we set the scheduler priority for a Cygwin process to "higher"
>>> than normal on start?
>>>
>>> Basically we want a Cygwin compatible script version of the Windows
>>> task manager feature Name/PID--->Details--->Set priority--->Higher
>>
>> Pretend the system is BSD or Linux and web search e.g. SO for that capability,
>> facility, or feature, then check Cygwin with Search Packages or:
>>
>> $ cygcheck -p usr/bin/nice
>> Found 6 matches for usr/bin/nice
> 
> I know about nice and renice, but I don't see whether it is working or not.

OFGS Why not try the command?  If it doesn't seem to do anything then try the 
command with the '-h' or '--help' option.  Or maybe try the canonical doc 'man 
nice'.  You shouldn't always need our help with stuff like this.

..mark

Re: Run a Cygwin process with "higher" scheduler priority

[Brian Inglis]

On 2023-10-14 07:47, Eliot Moss via Cygwin wrote:
> On 10/14/2023 7:39 AM, Cedric Blancher via Cygwin wrote:
>> On Fri, 11 Aug 2023 at 19:14, Brian Inglis wrote:
>>> On 2023-08-11 09:44, Cedric Blancher via Cygwin wrote:
>>>> How can we set the scheduler priority for a Cygwin process to "higher"
>>>> than normal on start?
>>>> Basically we want a Cygwin compatible script version of the Windows
>>>> task manager feature Name/PID--->Details--->Set priority--->Higher
>>> Pretend the system is BSD or Linux and web search e.g. SO for that capability,
>>> facility, or feature, then check Cygwin with Search Packages or:
>>> $ cygcheck -p usr/bin/nice
>>> Found 6 matches for usr/bin/nice
>> I know about nice and renice, but I don't see whether it is working or not.
>>> coreutils-debuginfo-8.26-2 - coreutils-debuginfo: Debug info for coreutils
>>> ...
>>> coreutils-9.0-1 - coreutils: GNU core utilities (includes fileutils, sh-utils
>>> and textutils)
>>> $ cygcheck -p usr/bin/renice
>>> Found 6 matches for usr/bin/renice
>>> util-linux-debuginfo-2.32.1-1 - util-linux-debuginfo: Debug info for util-linux
>>> util-linux-debuginfo-2.33.1-1 - util-linux-debuginfo: Debug info for util-linux
>>> util-linux-debuginfo-2.33.1-2 - util-linux-debuginfo: Debug info for util-linux
>>> util-linux-2.32.1-1 - util-linux: Collection of basic system utilities
>>> util-linux-2.33.1-1 - util-linux: Collection of basic system utilities
>>> util-linux-2.33.1-2 - util-linux: Collection of basic system utilities
>>> $ cygcheck -p usr/bin/chrt
>>> Found 2 matches for usr/bin/chrt
>>> util-linux-debuginfo-2.33.1-2 - util-linux-debuginfo: Debug info for util-linux
>>> util-linux-2.33.1-2 - util-linux: Collection of basic system utilities
>>> $ cygcheck -p usr/bin/taskset
>>> Found 2 matches for usr/bin/taskset
>>> util-linux-debuginfo-2.33.1-2 - util-linux-debuginfo: Debug info for util-linux
>>> util-linux-2.33.1-2 - util-linux: Collection of basic system utilities
>>> so you may need to install util-linux (coreutils is already installed as a base
>>> package for Cygwin) then:
>>>          $ man nice renice taskset chrt
>> chrt does not work, the syscalls for realtime seem to be not implemented.
>>> You may need to run these from an elevated admin shell for other user ids,
>>> unowned processes, or higher (negative) priority.
>>> It has been years since I tried these so can no longer remember if -20
>>> corresponds to Windows "RealTime" or if you need to use PowerShell to set 
>>> that e.g.
>>>          $proc   = Get-Process -ProcessName "..."
>>>          $proc.PriorityClass     = "RealTime"
>>> and that needs to be done from an elevated admin (Power)Shell.
>>> Of course, never set that on any system except on a very idle, very I/O bound,
>>> well tested process, such as ntpd, that needs stably fast interrupt service and
>>> non-preemptible cpu access for ms every few seconds, preferably on a single or
>>> few cpus to which affinity is set.
>> Is there anything in /proc which can tell me the current *Windows*
>> scheduler priority level? Or a command line tool?
> I recall getting taskset going in util-linux a while back, but I don't
> recall working on priority related things.  You could look into the
> cygwin source code to see how Windows priorities relate to the priority
> values in Cygwin.  Then you may be able just to use /proc/[pid]/stat
> read out what you want.

ISTR testing nice/renice, and found it was a simple priority mapping to/from 
Unix to Windows Idle to RealTime (at the time, process Affinity was not 
supported, so went with a PowerShell startup script instead); see:

https://cygwin.com/git/?p=newlib-cygwin.git;a=blob;f=winsup/cygwin/sched.cc#l107

https://cygwin.com/git/?p=newlib-cygwin.git;a=blob;f=winsup/cygwin/sched.cc#l234

https://cygwin.com/git/?p=newlib-cygwin.git;a=blob;f=winsup/cygwin/sched.cc#l277

They are documented in proc(5) /proc/PID/stat fields 18 priority and 19 nice 
typically 20 and 0, as shown by `top` PR and NI, shown by `procps -l` as 80 and 
0, and not shown by Cygwin `ps`.

-- 
Take care. Thanks, Brian Inglis              Calgary, Alberta, Canada

La perfection est atteinte                   Perfection is achieved
non pas lorsqu'il n'y a plus rien à ajouter  not when there is no more to add
mais lorsqu'il n'y a plus rien à retirer     but when there is no more to cut
                                 -- Antoine de Saint-Exupéry

Re: Run a Cygwin process with "higher" scheduler priority

[Christian Franke]

Brian Inglis via Cygwin wrote:
> On 2023-10-14 07:47, Eliot Moss via Cygwin wrote:
>> On 10/14/2023 7:39 AM, Cedric Blancher via Cygwin wrote:
>>> On Fri, 11 Aug 2023 at 19:14, Brian Inglis wrote:
>>>> ...
>>>
>>>> ...
>>>> $ cygcheck -p usr/bin/chrt
>>>> Found 2 matches for usr/bin/chrt
>>>> util-linux-debuginfo-2.33.1-2 - util-linux-debuginfo: Debug info 
>>>> for util-linux
>>>> util-linux-2.33.1-2 - util-linux: Collection of basic system utilities
>>>> $ cygcheck -p usr/bin/taskset
>>>> Found 2 matches for usr/bin/taskset
>>>> util-linux-debuginfo-2.33.1-2 - util-linux-debuginfo: Debug info 
>>>> for util-linux
>>>> util-linux-2.33.1-2 - util-linux: Collection of basic system utilities
>>>> so you may need to install util-linux (coreutils is already 
>>>> installed as a base
>>>> package for Cygwin) then:
>>>>          $ man nice renice taskset chrt
>>> chrt does not work, the syscalls for realtime seem to be not 
>>> implemented.

These are partly implemented, but sched_setscheduler() always fails with 
ENOSYS because scheduler policy (SCHED_*) cannot be changed on Windows. 
Changing priority only with sched_setparam() would work, but this is not 
used by chrt.


>>>> You may need to run these from an elevated admin shell for other 
>>>> user ids,
>>>> unowned processes, or higher (negative) priority.
>>>> It has been years since I tried these so can no longer remember if -20
>>>> corresponds to Windows "RealTime" or if you need to use PowerShell 
>>>> to set that e.g.
>>>>          $proc   = Get-Process -ProcessName "..."
>>>>          $proc.PriorityClass     = "RealTime"
>>>> and that needs to be done from an elevated admin (Power)Shell.
>>>> Of course, never set that on any system except on a very idle, very 
>>>> I/O bound,
>>>> well tested process, such as ntpd, that needs stably fast interrupt 
>>>> service and
>>>> non-preemptible cpu access for ms every few seconds, preferably on 
>>>> a single or
>>>> few cpus to which affinity is set.
>>> Is there anything in /proc which can tell me the current *Windows*
>>> scheduler priority level? Or a command line tool?
>> I recall getting taskset going in util-linux a while back, but I don't
>> recall working on priority related things.  You could look into the
>> cygwin source code to see how Windows priorities relate to the priority
>> values in Cygwin.  Then you may be able just to use /proc/[pid]/stat
>> read out what you want.
>
> ISTR testing nice/renice, and found it was a simple priority mapping 
> to/from Unix to Windows Idle to RealTime (at the time, process 
> Affinity was not supported, so went with a PowerShell startup script 
> instead); see:
>
> https://cygwin.com/git/?p=newlib-cygwin.git;a=blob;f=winsup/cygwin/sched.cc#l107 
>
>
> https://cygwin.com/git/?p=newlib-cygwin.git;a=blob;f=winsup/cygwin/sched.cc#l234 
>
>
> https://cygwin.com/git/?p=newlib-cygwin.git;a=blob;f=winsup/cygwin/sched.cc#l277 
>

The above maps priorities for sched_*() API. The mapping for nice() and 
get/setpriority() is done here:

https://cygwin.com/git/?p=newlib-cygwin.git;a=blob;f=winsup/cygwin/miscfuncs.cc;h=767384f#l110


> They are documented in proc(5) /proc/PID/stat fields 18 priority and 
> 19 nice typically 20 and 0, as shown by `top` PR and NI, shown by 
> `procps -l` as 80 and 0, and not shown by Cygwin `ps`.

On Cygwin, field 18 is always equal to (field_19 + 20). The priority 
value returned by sched_getparam() is different and could be shown with 
'chrt -p PID'.

The output from the command 'nice' without parameter may differ from 
/proc/PID/stat field 19 because the latter always reinterprets the 
current Windows prio class.

This script prints a table of 'nice' outputs, /proc/PID/stat fields 19 
and 18, result of sched_getparam() and corresponding Windows prio class 
for different 'nice -n ...' commands:

#!/bin/bash
echo "COMMAND    : NICE  STAT STPRI RTPRI  WINPRI"
for i in {-21..20}; do
   nice -n $i sh -e -c '
     n=$(nice)
     s=$(cut -d" " -f19 /proc/$$/stat)
     p=$(cut -d" " -f18 /proc/$$/stat)
     r=$(LC_MESSAGES=C chrt -p $$ | sed -n "s,^.*priority: ,,p")
     case $r in
       3)  c="IDLE_PRIORITY_CLASS" ;;
       9)  c="BELOW_NORMAL_PRIORITY_CLASS" ;;
       15) c="NORMAL_PRIORITY_CLASS" ;;
       21) c="ABOVE_NORMAL_PRIORITY_CLASS" ;;
       27) c="HIGH_PRIORITY_CLASS" ;;
       32) c="REALTIME_PRIORITY_CLASS" ;;
       *)  c="?" ;;
     esac
     printf "nice -n %3d:%5d %5d %5d %5d  %s\\n" \
            "'$i'" "$n" "$s" "$p" "$r" "$c"
   '
done

-- 
Regards,
Christian

Re: Run a Cygwin process with "higher" scheduler priority

[Chris Wagner]

On 2023-10-14 7:39 am, Cedric Blancher via Cygwin wrote:
> 
> I know about nice and renice, but I don't see whether it is working or 
> not.
> 

> Is there anything in /proc which can tell me the current *Windows*
> scheduler priority level? Or a command line tool?
> 
> Ced

Iarn's TaskInfo will show you the real Windows priority (and let you 
change it and even suspend processes) along with a boatload of other 
highly useful stats.  That will let you validate anything Cygwin claims 
it did.

https://www.iarsn.com/taskinfo.html

It's old but it still works and I run it continuously.

Re: Run a Cygwin process with "higher" scheduler priority

[Backwoods BC]

On Sat, Oct 14, 2023 at 4:41 AM Cedric Blancher via Cygwin
<cygwin@cygwin.com> wrote:
> Is there anything in /proc which can tell me the current *Windows*
> scheduler priority level? Or a command line tool?

'pslist' from Sysinternals (owned by MS) will tell you the Windows priority.

<https://learn.microsoft.com/en-ca/sysinternals/downloads/pslist>

As for mapping Cygwin priorities to Windows, I ran a test using
'renice' to change the priority of a job and found the follosing
non-linear mapping:
Cygwin priority   1-3 is Windows priority 8
Cygwin priority  4-11 is Windows priority 6
Cygwin priority 12-19 is Windows priority 4

I only tested priorities 1 to 19.