Thread Scheduler

Thread Scheduler

[Mahmood Naderan]

Hi
Maybe this is a noob question...
Where in the linux kernel source (2.6), the 

thread scheduler has been implemented? Searching 

the web shows that there should sched_fair.c but 

I can not find that in the source directory (the 
kernel source has been installed). 


Basically, I want to know which part of the code 

calculated the priorities of the available 

threads and select them for running?


Regards,
Mahmood 

Re: Thread Scheduler

[Mike Galbraith]

On Wed, 2014-03-19 at 02:57 -0700, Mahmood Naderan wrote: 
> 
> Hi
> Maybe this is a noob question...
> Where in the linux kernel source (2.6), the 
> 
> thread scheduler has been implemented? Searching 
> 
> the web shows that there should sched_fair.c but 
> 
> I can not find that in the source directory (the 
> kernel source has been installed). 

The scheduler recently moved to kernel/sched directory.  For older
kernels, it's kernel/sched_*.

-Mike

Re: Thread Scheduler

[Mahmood Naderan]

>On Wednesday, March 19, 2014 3:57 PM, Mike Galbraith <umgwanakikbuti@gmail.com> wrote:
>On Wed, 2014-03-19 at 02:57 -0700, Mahmood Naderan wrote: 
>> 
>> Hi
>> Maybe this is a noob question...
>> Where in the linux kernel source (2.6), the 
>> 
>> thread scheduler has been implemented? Searching 
>> 
>> the web shows that there should sched_fair.c but 
>> 
>> I can not find that in the source directory (the 
>> kernel source has been installed). 
>
>The scheduler recently moved to kernel/sched directory.  For older
>kernels, it's kernel/sched_*.
>
>-Mike


Please see this information

[root@tiger ~]# uname -a
Linux tiger 2.6.32-279.5.1.el6.x86_64 #1 SMP Tue Aug 14 16:11:42 CDT 2012 x86_64 x86_64 x86_64 GNU/Linux

[root@tiger ~]# ls /usr/src/kernels/2.6.32-279.5.1.el6.x86_64/kernel/
events  gcov  irq  Kconfig.freezer  Kconfig.hz  Kconfig.preempt  Makefile  power  time  trace

[root@tiger ~]# cd /usr/src/kernels/2.6.32-279.5.1.el6.x86_64/

[root@tiger 2.6.32-279.5.1.el6.x86_64]# find . -name sched*
./net/sched
./include/asm-generic/bitops/sched.h
./include/config/group/sched.h
./include/config/cgroup/sched.h
./include/config/schedstats.h
./include/config/fair/group/sched.h
./include/config/have/unstable/sched
./include/config/net/sched.h
./include/config/rt/group/sched.h
./include/config/sched
./include/trace/events/sched.h
./include/linux/sched.h
./include/linux/sunrpc/sched.h




Do you mean include/linux/sched.h ?
Where is he implementation then?

 
Regards,
Mahmood

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Re: Thread Scheduler

[Jack Carrozzo]

On Wed, Mar 19, 2014 at 7:34 AM, Mahmood Naderan <nt_mahmood@yahoo.com> wrote:
>
> [...]
> Do you mean include/linux/sched.h ?
> Where is he implementation then?

Your kernel source is incomplete. You can fetch a vanilla kernel
tarball from http://kernel.org.

jackc@kdev0 ~ $ ls /usr/src/linux-2.6.10/kernel/|grep sched
sched.c
jackc@kdev0 ~ $ ls /usr/src/linux-3.13.5/kernel/sched/
auto_group.c  completion.c  cpuacct.h  cputime.c  features.h   proc.c
 stats.c      wait.c
auto_group.h  core.c        cpupri.c   debug.c    idle_task.c  rt.c     stats.h
clock.c       cpuacct.c     cpupri.h   fair.c     Makefile     sched.h
 stop_task.c

-J

Re: Thread Scheduler

[Mahmood Naderan]

On Wednesday, March 19, 2014 4:36 PM, Jack Carrozzo <jack@crepinc.com> wrote:

>On Wed, Mar 19, 2014 at 7:34 AM, Mahmood Naderan <nt_mahmood@yahoo.com> wrote:
>
>>
>> [...]
>> Do you mean include/linux/sched.h ?
>> Where is he implementation then?
>
>Your kernel source is incomplete. You can fetch a vanilla kernel
>tarball from http://kernel.org.
>
>jackc@kdev0 ~ $ ls /usr/src/linux-2.6.10/kernel/|grep sched
>sched.c
>jackc@kdev0 ~ $ ls /usr/src/linux-3.13.5/kernel/sched/
>auto_group.c  completion.c  cpuacct.h  cputime.c  features.h   proc.c
>stats.c      wait.c
>auto_group.h  core.c        cpupri.c   debug.c    idle_task.c  rt.c     stats.h
>clock.c       cpuacct.c     cpupri.h   fair.c     Makefile     sched.h
>stop_task.c
>
>-J


OK I installed the full source and now can see the sched*.c files
One more question. Is it possible to dynamically change the scheduling policy, e.g from fair to clock? Basically, I am trying to find the direction on *how to invoke a new scheduling policy*?

Re: Thread Scheduler

[Mike Galbraith]

On Wed, 2014-03-19 at 13:01 -0700, Mahmood Naderan wrote:
> 
> One more question. Is it possible to dynamically change the scheduling
> policy, e.g from fair to clock?

marge:~ # man -k setscheduler getscheduler
sched_setscheduler (2) - set and get scheduling policy/parameters
sched_setscheduler (3p) - set scheduling policy and parameters (REALTIME)
sched_getscheduler (2) - set and get scheduling policy/parameters
sched_getscheduler (3p) - get scheduling policy (REALTIME)

Re: Thread Scheduler

[Mahmood Naderan]

>On Thursday, March 20, 2014 6:53 AM, Mike Galbraith <umgwanakikbuti@gmail.com> wrote:
>
>marge:~ # man -k setscheduler getscheduler
>sched_setscheduler (2) - set and get scheduling policy/parameters
>sched_setscheduler (3p) - set scheduling policy and parameters (REALTIME)
>sched_getscheduler (2) - set and get scheduling policy/parameters
>sched_getscheduler (3p) - get scheduling policy (REALTIME)





OK I read them and it seems that in order to change the scheduler, I have to write a C code and call the sched_set* functions. Please correct that if I am wrong.

So in order to use my custom scheduler, I have to do the following steps.

1- Write my  code using the APIs and save that in kernel/sched_custom.c
2- Invoke sched_custom.c in kernel/sched.c
3- Recompile the kernel source
4- Reboot using the new kernel
5- write a C code and call sched_setschedule() to use my scheduler.

Is that all? Your reply is appreciated.


Regards,
Mahmood 

Re: Thread Scheduler

[Mark Knecht]

On Sun, Mar 23, 2014 at 4:01 AM, Mahmood Naderan <nt_mahmood@yahoo.com> wrote:
>
>
>
>
>
>
>>On Thursday, March 20, 2014 6:53 AM, Mike Galbraith <umgwanakikbuti@gmail.com> wrote:
>>
>>marge:~ # man -k setscheduler getscheduler
>>sched_setscheduler (2) - set and get scheduling policy/parameters
>>sched_setscheduler (3p) - set scheduling policy and parameters (REALTIME)
>>sched_getscheduler (2) - set and get scheduling policy/parameters
>>sched_getscheduler (3p) - get scheduling policy (REALTIME)
>
>
>
>
>
> OK I read them and it seems that in order to change the scheduler, I have to write a C code and call the sched_set* functions. Please correct that if I am wrong.
>
> So in order to use my custom scheduler, I have to do the following steps.
>
> 1- Write my  code using the APIs and save that in kernel/sched_custom.c
> 2- Invoke sched_custom.c in kernel/sched.c
> 3- Recompile the kernel source
> 4- Reboot using the new kernel
> 5- write a C code and call sched_setschedule() to use my scheduler.
>
> Is that all? Your reply is appreciated.
>
>
> Regards,
> Mahmood
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> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
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In terms of changing the scheduler I think that you possibly missed
reading Documentation/block/switching-sched.txt in the kernel's
documentation directory.

HTH,
Mark

Re: Thread Scheduler

[Mahmood Naderan]

On Sunday, March 23, 2014 6:35 PM, Mark Knecht <markknecht@gmail.com> wrote:
>In terms of changing the scheduler I think that you possibly missed
>reading Documentation/block/switching-sched.txt in the kernel's
>documentation directory.
>
>HTH,
>Mark

That is IO scheduler. Can we use the same for threads/processes? 
echo deadline > /proc/10100

Or something like that?


 
Regards,
Mahmood

Re: Thread Scheduler

[Mark Knecht]

On Sun, Mar 23, 2014 at 7:27 AM, Mahmood Naderan <nt_mahmood@yahoo.com> wrote:
>
>
>
>
> On Sunday, March 23, 2014 6:35 PM, Mark Knecht <markknecht@gmail.com> wrote:
>>In terms of changing the scheduler I think that you possibly missed
>>reading Documentation/block/switching-sched.txt in the kernel's
>>documentation directory.
>>
>>HTH,
>>Mark
>
> That is IO scheduler. Can we use the same for threads/processes?
> echo deadline > /proc/10100
>
> Or something like that?
>
>
>
> Regards,
> Mahmood
>
Sorry, you're right. My mistake.

- Mark

Re: Thread Scheduler

[Andreas Mohr]

Hi,

> OK I read them and it seems that in order to change the scheduler, I have to write a C code and call the sched_set* functions. Please correct that if I am wrong.
> 
> So in order to use my custom scheduler, I have to do the following steps.
> 
> 1- Write my  code using the APIs and save that in kernel/sched_custom.c
> 2- Invoke sched_custom.c in kernel/sched.c
> 3- Recompile the kernel source
> 4- Reboot using the new kernel
> 5- write a C code and call sched_setschedule() to use my scheduler.
> 
> Is that all? Your reply is appreciated.

No, AFAIK these are *user-space* APIs, thus they're supposed to be used by
applications (correct me if I'm wrong).


So the question would be what exactly you're trying to achieve:
either you want to actively modify the kernel-side scheduler sources,
in which case these APIs probably are not what you want (to use there),
or you're trying to modify scheduling configuration of user-space applications,
in which case they possibly are.
Or you want both, in which case you probably
modify kernel scheduler implementation *and* use sched_*() in user-space
with the intent to ensure that that modified scheduler implementation
gets chosen.

HTH,

Andreas Mohr