real time question : RR vs FF?

[victorvictor]

Hello

I have made an app that displays the harmonics in 3d.

I want to be able to run it in real-time; I have used the 'rtpool-test' code from the gstreamer core examples (streams->rtpool-test.c) and it works. However, I have seen that this grants me a priority of 90 with a 'RR' policy. Is it possible to change the code code to get 'FIFO' policy? If yes, please how could I do this? I have tied to use the set_schedparam code, but I got the 'Invalid argument' during 'pthread_attr_setschedparam (&attr, &sched)' error... (as well as starting the app with 'chrt -r -p my-pid')

Another question : this code grants real time for Gstreamer code, but what about other code code (not Gstreamer) that follows it? The app is written like this : GTK GUI with a 'Play" button, that starts playing the sound with Gstreamer, and the 'spectrum' element send messages to the bus; everytime the "message handler" function retrives the values of the spectrum, there is a call to a function that display the values of the spectrum in a SDL/OpenGL window. My question is : is the display in the SDL/OpenGL window done also with the RR policy or back with TS policy?

When I run the app (its name is 'spectrum3d', then when I run 'ps -cLe' in a terminal to see all the threads of the app, I see this :

 5265  5265 TS   19 pts/0    00:00:01 spectrum3d
 5265  5267 TS   19 pts/0    00:00:00 threaded-ml
 5265  5268 TS   19 pts/0    00:00:00 threaded-ml
 5265  5270 TS   19 pts/0    00:00:00 task0
 5265  5271 TS   19 pts/0    00:00:00 spectrum3d
 5265  5272 RR   90 pts/0    00:00:01 alsasrc:src

The 1st pid is the Gtk GUI; the last one must be the gstreamer sound reading, since its policy is RR; but I don't know what the other pid represent...

thanks for your help

Victor

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[Stefan Sauer]

Am 28.04.2011 05:34, schrieb Victor henri:

> Hello
>
> I have made an app that displays the harmonics in 3d.
>
> I want to be able to run it in real-time; I have used the 'rtpool-test' code
> from the gstreamer core examples (streams->rtpool-test.c) and it works. However,
> I have seen that this grants me a priority of 90 with a 'RR' policy. Is it
> possible to change the code code to get 'FIFO' policy? If yes, please how could
> I do this? I have tied to use the set_schedparam code, but I got the 'Invalid
> argument' during 'pthread_attr_setschedparam (&attr, &sched)' error... (as well
> as starting the app with 'chrt -r -p my-pid')

You need to have permission to swicth your app to that (e.g. try the chrt call
as root). Now the better question is why you want to do it. Before I go depper,
if would be good if you could tell what your expectation is.

Stefan

>
> Another question : this code grants real time for Gstreamer code, but what about
> other code code (not Gstreamer) that follows it? The app is written like this :
> GTK GUI with a 'Play" button, that starts playing the sound with Gstreamer, and
> the 'spectrum' element send messages to the bus; everytime the "message handler"
> function retrives the values of the spectrum, there is a call to a function that
> display the values of the spectrum in a SDL/OpenGL window. My question is : is
> the display in the SDL/OpenGL window done also with the RR policy or back with
> TS policy?
>
> When I run the app (its name is 'spectrum3d', then when I run 'ps -cLe' in a
> terminal to see all the threads of the app, I see this :
>
>  5265  5265 TS   19 pts/0    00:00:01 spectrum3d
>  5265  5267 TS   19 pts/0    00:00:00 threaded-ml
>  5265  5268 TS   19 pts/0    00:00:00 threaded-ml
>  5265  5270 TS   19 pts/0    00:00:00 task0
>  5265  5271 TS   19 pts/0    00:00:00 spectrum3d
>  5265  5272 RR   90 pts/0    00:00:01 alsasrc:src
>
> The 1st pid is the Gtk GUI; the last one must be the gstreamer sound reading,
> since its policy is RR; but I don't know what the other pid represent...
>
> thanks for your help
>
> Victor
>
>
>
> _______________________________________________
> gstreamer-devel mailing list
> [hidden email]
> http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel

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[victorvictor]

Hello Stefan and thank you for your answer

>> I have made an app that displays the harmonics in 3d.
>>
>> I want to be able to run it in real-time; I have used the 'rtpool-test' code
>> from the gstreamer core examples (streams->rtpool-test.c) and it works. However,
>> I have seen that this grants me a priority of 90 with a 'RR' policy. Is it
>> possible to change the code code to get 'FIFO' policy? If yes, please how could
>> I do this? I have tied to use the set_schedparam code, but I got the 'Invalid
>> argument' during 'pthread_attr_setschedparam (&attr, &sched)' error... (as well
>> as starting the app with 'chrt -r -p my-pid')
>
> You need to have permission to swicth your app to that (e.g. try the chrt call
> as root).

It doesn't work; both starting the app with "sudo chrt -r my_app" and using the 'set_schedparam' function don't work : I get the error : "pthread_attr_setschedparam (&attr, &sched)" and this has already been reported I think.
I have seen a post at the gstreamer list about this, and they advised to use the 'rtpool-test' code; I did it and it worked;

>Now the better question is why you want to do it. Before I go depper,
> if would be good if you could tell what your expectation is.

The app displays in a 3D graph the harmonics of the sound sound captured from the microphone;  since it is 3d (hence cpu and gpu consuming) and a real-time analysis, I'd like to start the app with the real-time policy to ensure that is has priority about other process that may slow it down; I'm well aware that running it in real time won't decrease its CPU and GPU use though

>
> Stefan
>
>>
>> Another question : this code grants real time for Gstreamer code, but what about
>> other code code (not Gstreamer) that follows it? The app is written like this :
>> GTK GUI with a 'Play" button, that starts playing the sound with Gstreamer, and
>> the 'spectrum' element send messages to the bus; everytime the "message handler"
>> function retrives the values of the spectrum, there is a call to a function that
>> display the values of the spectrum in a SDL/OpenGL window. My question is : is
>> the display in the SDL/OpenGL window done also with the RR policy or back with
>> TS policy?
>>
>> When I run the app (its name is 'spectrum3d', then when I run 'ps -cLe' in a
>> terminal to see all the threads of the app, I see this :
>>
>> 5265 5265 TS 19 pts/0 00:00:01 spectrum3d
>> 5265 5267 TS 19 pts/0 00:00:00 threaded-ml
>> 5265 5268 TS 19 pts/0 00:00:00 threaded-ml
>> 5265 5270 TS 19 pts/0 00:00:00 task0
>> 5265 5271 TS 19 pts/0 00:00:00 spectrum3d
>> 5265 5272 RR 90 pts/0 00:00:01 alsasrc:src
>>
>> The 1st pid is the Gtk GUI; the last one must be the gstreamer sound reading,
>> since its policy is RR; but I don't know what the other pid represent...
>>

Regarding this, do you think running the Gstreamer thread in real-time is enough to give also real-time display with openGL, since the display function is called from the message handler function of Gstreamer

Thank you for helping me

Victor

     
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[victorvictor]

I answer to myself

It was quite easy to find...
In the 'testrtpool.c' file, in the 'default-push' function, I just had to replace "SCHED_RR" by "SCHED_FIFO"
On the other hand, 'param.sched_priority' is set to to 50, which can be changed also according to the priority one wants to give to the process;

Victor

---

From: [hidden email]
To: [hidden email]
Subject: real time question : RR vs FF?
Date: Thu, 28 Apr 2011 04:34:39 +0200

Hello

I have made an app that displays the harmonics in 3d.

I want to be able to run it in real-time; I have used the 'rtpool-test' code from the gstreamer core examples (streams->rtpool-test.c) and it works. However, I have seen that this grants me a priority of 90 with a 'RR' policy. Is it possible to change the code code to get 'FIFO' policy? If yes, please how could I do this? I have tied to use the set_schedparam code, but I got the 'Invalid argument' during 'pthread_attr_setschedparam (&attr, &sched)' error... (as well as starting the app with 'chrt -r -p my-pid')

Another question : this code grants real time for Gstreamer code, but what about other code code (not Gstreamer) that follows it? The app is written like this : GTK GUI with a 'Play" button, that starts playing the sound with Gstreamer, and the 'spectrum' element send messages to the bus; everytime the "message handler" function retrives the values of the spectrum, there is a call to a function that display the values of the spectrum in a SDL/OpenGL window. My question is : is the display in the SDL/OpenGL window done also with the RR policy or back with TS policy?

When I run the app (its name is 'spectrum3d', then when I run 'ps -cLe' in a terminal to see all the threads of the app, I see this :

 5265  5265 TS   19 pts/0    00:00:01 spectrum3d
 5265  5267 TS   19 pts/0    00:00:00 threaded-ml
 5265  5268 TS   19 pts/0    00:00:00 threaded-ml
 5265  5270 TS   19 pts/0    00:00:00 task0
 5265  5271 TS   19 pts/0    00:00:00 spectrum3d
 5265  5272 RR   90 pts/0    00:00:01 alsasrc:src

The 1st pid is the Gtk GUI; the last one must be the gstreamer sound reading, since its policy is RR; but I don't know what the other pid represent...

thanks for your help

Victor

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[Stefan Sauer]

Am 30.04.2011 11:24, schrieb Victor henri:
> I answer to myself
>
> It was quite easy to find...
> In the 'testrtpool.c' file, in the 'default-push' function, I just had to
> replace "SCHED_RR" by "SCHED_FIFO"
> On the other hand, 'param.sched_priority' is set to to 50, which can be changed
> also according to the priority one wants to give to the process;

I hope you have a good reason for using SCHED_FIFO. 1st I hope you understand
that you will only get scheduling priority, I you are not running fast enough,
this is *not* the solution. 2nd I hope you understand the dangers of SCHED_FIFO
vs. SCHED_RR.

Stefan

>
> Victor
>
> --------------------------------------------------------------------------------
> From: [hidden email]
> To: [hidden email]
> Subject: real time question : RR vs FF?
> Date: Thu, 28 Apr 2011 04:34:39 +0200
>
> Hello
>
> I have made an app that displays the harmonics in 3d.
>
> I want to be able to run it in real-time; I have used the 'rtpool-test' code
> from the gstreamer core examples (streams->rtpool-test.c) and it works. However,
> I have seen that this grants me a priority of 90 with a 'RR' policy. Is it
> possible to change the code code to get 'FIFO' policy? If yes, please how could
> I do this? I have tied to use the set_schedparam code, but I got the 'Invalid
> argument' during 'pthread_attr_setschedparam (&attr, &sched)' error... (as well
> as starting the app with 'chrt -r -p my-pid')
>
> Another question : this code grants real time for Gstreamer code, but what about
> other code code (not Gstreamer) that follows it? The app is written like this :
> GTK GUI with a 'Play" button, that starts playing the sound with Gstreamer, and
> the 'spectrum' element send messages to the bus; everytime the "message handler"
> function retrives the values of the spectrum, there is a call to a function that
> display the values of the spectrum in a SDL/OpenGL window. My question is : is
> the display in the SDL/OpenGL window done also with the RR policy or back with
> TS policy?
>
> When I run the app (its name is 'spectrum3d', then when I run 'ps -cLe' in a
> terminal to see all the threads of the app, I see this :
>
>  5265  5265 TS   19 pts/0    00:00:01 spectrum3d
>  5265  5267 TS   19 pts/0    00:00:00 threaded-ml
>  5265  5268 TS   19 pts/0    00:00:00 threaded-ml
>  5265  5270 TS   19 pts/0    00:00:00 task0
>  5265  5271 TS   19 pts/0    00:00:00 spectrum3d
>  5265  5272 RR   90 pts/0    00:00:01 alsasrc:src
>
> The 1st pid is the Gtk GUI; the last one must be the gstreamer sound reading,
> since its policy is RR; but I don't know what the other pid represent...
>
> thanks for your help
>
> Victor
>
> _______________________________________________ gstreamer-devel mailing list
> [hidden email]
> http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel
>
>
>
> _______________________________________________
> gstreamer-devel mailing list
> [hidden email]
> http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel

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[victorvictor]

Hello Stefan and thank you for your answer

> > It was quite easy to find...
> > In the 'testrtpool.c' file, in the 'default-push' function, I just had to
> > replace "SCHED_RR" by "SCHED_FIFO"
> > On the other hand, 'param.sched_priority' is set to to 50, which can be changed
> > also according to the priority one wants to give to the process;
>
> I hope you have a good reason for using SCHED_FIFO. 1st I hope you understand
> that you will only get scheduling priority, I you are not running fast enough,
> this is *not* the solution

My app is very demanding since it involves realtime (and very fast) analysis and display of the data's. Although my machine is powerfull enough, I suppose that on machine that are not powerfull enough, this could cause lock up.

. 2nd I hope you understand the dangers of SCHED_FIFO
> vs. SCHED_RR.
>


As far as I know, the  main difference is that the SCHED_FIFO cannot be prempted
unless another process of higher priority shows up in the execution
queue; and
SCHED_RR can be preempted by a time quantum...

I apreciate your warning and get back to the RR policy for now and investigate more. Indeed it may be more safe.

Thank you so much for sharing

Victor
     
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[Michael Nazzareno Trimarchi]

Hi
On 05/01/2011 05:54 PM, Victor henri wrote:

>
> Hello Stefan and thank you for your answer
>
>>> It was quite easy to find...
>>> In the 'testrtpool.c' file, in the 'default-push' function, I just had to
>>> replace "SCHED_RR" by "SCHED_FIFO"
>>> On the other hand, 'param.sched_priority' is set to to 50, which can be changed
>>> also according to the priority one wants to give to the process;
>>
>> I hope you have a good reason for using SCHED_FIFO. 1st I hope you understand
>> that you will only get scheduling priority, I you are not running fast enough,
>> this is *not* the solution
>
> My app is very demanding since it involves realtime (and very fast) analysis and display of the data's. Although my machine is powerfull enough, I suppose that on machine that are not powerfull enough, this could cause lock up.
>
> . 2nd I hope you understand the dangers of SCHED_FIFO
>> vs. SCHED_RR.
>>
>
>
> As far as I know, the  main difference is that the SCHED_FIFO cannot be prempted
> unless another process of higher priority shows up in the execution
> queue; and
> SCHED_RR can be preempted by a time quantum...
>

Can you give a try to SCHED_DEADLINE for your application?

Michael Trimarchi

> I apreciate your warning and get back to the RR policy for now and investigate more. Indeed it may be more safe.
>
> Thank you so much for sharing
>
> Victor
>      
> _______________________________________________
> gstreamer-devel mailing list
> [hidden email]
> http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel

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