Re: scheduler/SCHED_FIFO behaviour

[Arun Srinivas]

I am not sure if my question was clear enough or I couldnt interpret you 
answer correctly.(If it was the case I apologise for that).

My question is, as I said I am measuring the schedule time difference 
between my 2 of my SCHED_FIFO process in schedule() .But, I get only one set 
of readings (i.e., schedule() is being called once which implies my process 
is being scheduled only once and run till completion)

Also, as I said my interrupts are being processed during this time.I 
inspected /proc/interrupts for this.So, my question was if interrupts heve 
been processed several times the 2 SCHED_FIFO process which has been 
interrupted must have been resecheduled several times and for this upon 
returning from the interrupt handler the schedule() function must have been 
called  several times to schedule the 2 process which were running.But, as I 
said I get only one reading??

From your reply, I come to understand that when an interrupt interrupts my 
user process.it runs straight way but upon return from the interrupt 
handler does it not call schedule() to again resume my interrupted process? 
Please help.

Thanks
arun

From: Steven Rostedt <[EMAIL PROTECTED]>
To: Arun Srinivas <[EMAIL PROTECTED]>
CC: [EMAIL PROTECTED], LKML 
Subject: Re: scheduler/SCHED_FIFO behaviour
Date: Mon, 04 Apr 2005 23:33:05 -0400
On Tue, 2005-04-05 at 07:46 +0530, Arun Srinivas wrote:
>
> So, what I want from the above code is whenever process1 or process2 is
> being scheduled measure the time and print the timedifference. But, when 
I
> run my 2 processes as SCHED_FIFO processes i get only one set of
> readingsindicating they have been scheduled only once and run till
> completion.
>
> But, as we saw above if interrupts have been processed they must have 
been
> scheduled several times(i.e., schedule() called several times). Is my
> measurement procedure not correct?

No! Interrupts are not scheduled. When an interrupt goes off, the
interrupt service routine (ISR) is executed. It doesn't need to be
scheduled. It runs right where it interrupted the CPU. That's why you
need to be careful about protecting data that ISRs manipulate with
spin_lock_irqsave. This not only protects against multiple CPUs, but
turns off interrupts so that an interrupt wont be called and one of the
ISRs modify the data you need to be atomic.
Your tasks are running and will be interrupted by an ISR, on return from
the routine, a check is made to see if your tasks should be preempted.
But since they are the highest running tasks and in FIFO mode, the check
determines that schedule should not be called.  So you will not see any
schedules while your tasks are running.
Now, if you where running Ingo's RT patch with PREEMPT_HARDIRQ enabled,
and your tasks were of lower priority than the ISR thread handlers, then
you would see the scheduling. Maybe that is what you want?
-- Steve

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Re: scheduler/SCHED_FIFO behaviour

[Arun Srinivas]

ok.My program runs for 30 sec. approx. I did
#!/bin/sh
cat /proc/interrupts
run_test
cat /proc/interrupts
and I see there is quite some difference in the numbers.meaning 
interrupts have been processed by the respective processor when my 
SCHED_FIFO processes have been running on both the cpu's.

But, then I am not sure why I am getting only 1 reading for the timediff. of 
schedule between my 2 processes.I do the following in my schedule() in 
sched.c:
( I make the kernel know the pid's of my 2 process...lets say pid1 and pid2)

/* in function schedule() in sched.c*/
schedule()
{
  need _resched:
   /* after now=sched_clock(); I insert my code 
here*/
 if(current->pid=pid1)
{
   time1=now;
 }
  elseif (current->pid=pid2)
{
   time2=now;
}
/*after i get the 2 values for time1 and 
time2*/
timediff= time1-time2;// or 
time2 - time1 which ever is greater*/
printk(KERN_ERR "%llu",timediff);
}

So, what I want from the above code is whenever process1 or process2 is 
being scheduled measure the time and print the timedifference. But, when I 
run my 2 processes as SCHED_FIFO processes i get only one set of 
readingsindicating they have been scheduled only once and run till 
completion.

But, as we saw above if interrupts have been processed they must have been 
scheduled several times(i.e., schedule() called several times). Is my 
measurement procedure not correct?

please help.
thanks
arun

From: Steven Rostedt <[EMAIL PROTECTED]>
To: Arun Srinivas <[EMAIL PROTECTED]>
CC: [EMAIL PROTECTED], LKML 
Subject: Re: scheduler/SCHED_FIFO behaviour
Date: Mon, 04 Apr 2005 19:17:04 -0400
On Tue, 2005-04-05 at 04:36 +0530, Arun Srinivas wrote:
> I am scheduling 2 SCHED_FIFO processes and set them affinity( process A 
runs
> on processor 1 and process B runs on processor 2), on a HT processor.(I 
did
> this cause I wanted to run them together).Now, in schedule() I measure 
the
> timedifference between when they are scheduled. I found that when I
> introduce these 2 processes as SCHED_FIFO they are
>
> 1)scheduled only once and run till completion ( they running time is 
around
> 2 mins.)

If they are the highest priority task, and running as FIFO this is the
proper behavior.
> 2)entire system appears frozenno mouse/key presses detected until 
the
> processes exit.
>

If X is not at a higher priority than the test you are running, it will
never get a chance to run.
> >From what I observed does it mean that even the OS / interrupt handler 
does
> not occur during the entire period of time these real time processes 
run??
> (as I said the processes run in minutes).

The interrupts do get processed. Now the bottom halves and tasklets may
be starved if they are set at a lower priority than your test (ie. the
ksoftirqd thread). But most likely they are processed too.
> How can I verify that?
>
#!/bin/sh
cat /proc/interrupts
run_test
cat /proc/interrupts
If the run_test takes 2 minutes, you should see a large difference in
the two outputs.
-- Steve
> Thanks
> Arun

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scheduler/SCHED_FIFO behaviour

[Arun Srinivas]

I am scheduling 2 SCHED_FIFO processes and set them affinity( process A runs 
on processor 1 and process B runs on processor 2), on a HT processor.(I did 
this cause I wanted to run them together).Now, in schedule() I measure the 
timedifference between when they are scheduled. I found that when I 
introduce these 2 processes as SCHED_FIFO they are

1)scheduled only once and run till completion ( they running time is around 
2 mins.)
2)entire system appears frozenno mouse/key presses detected until the 
processes exit.

From what I observed does it mean that even the OS / interrupt handler does 
not occur during the entire period of time these real time processes run?? 
(as I said the processes run in minutes).
How can I verify that?

Thanks
Arun
From: Steven Rostedt <[EMAIL PROTECTED]>
To: Arun Srinivas <[EMAIL PROTECTED]>
CC: [EMAIL PROTECTED], LKML 
Subject: Re: sched /HT processor
Date: Sun, 03 Apr 2005 19:08:06 -0400
On Mon, 2005-04-04 at 04:22 +0530, Arun Srinivas wrote:
> Thanks. yes, a reschedule may not take place after a ms, if the 
currently
> running task cannot be preempted by another task.
>
> (1) But, can a reschedule happen within a millisec (or once a process is
> scheduled can schedule() be called before the next millisec.) ?
>

Yes.  For example: a high priority task may be waiting for some IO to
come in. Right after the normal timer interrupt scheduled another task,
the IO may come in and wake the high priority process up. This process
will preempt the other task right away. (ie. less than 1 ms).
> 2) Also in case argument (1) is not true, and I want rescheduling to be 
done
> (i.e., schedule() called) in less than 1 ms , can I directly change the 
HZ
> value in  and recompile my kernel so that my timer
> interrupt will occur frequently?
>

Well, 1) is true, but you can also increase HZ over 1000 if you like,
but that will usually cause more overhead, since, although a schedule
may not take place every HZ, a timer interrupt will.
-- Steve

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Re: sched /HT processor

[Arun Srinivas]

Thanks. yes, a reschedule may not take place after a ms, if the currently 
running task cannot be preempted by another task.

(1) But, can a reschedule happen within a millisec (or once a process is 
scheduled can schedule() be called before the next millisec.) ?

2) Also in case argument (1) is not true, and I want rescheduling to be done 
(i.e., schedule() called) in less than 1 ms , can I directly change the HZ 
value in  and recompile my kernel so that my timer 
interrupt will occur frequently?

Thanks
Arun
From: Steven Rostedt <[EMAIL PROTECTED]>
To: Jesper Juhl <[EMAIL PROTECTED]>
CC: Arun Srinivas <[EMAIL PROTECTED]>,LKML 

Subject: Re: sched /HT processor
Date: Sun, 03 Apr 2005 11:31:03 -0400

On Sun, 2005-04-03 at 13:17 +0200, Jesper Juhl wrote:
>
> A reschedule can happen once every ms, but also upon returning to
> userspace and when returning from an interrupt handler, and also when
> something in the kernel explicitly calls schedule() or sleeps (which in
> turn results in a call to schedule()). And each CPU runs schedule()
> independently.
> At least that's my understanding of it - if I'm wrong I hope someone on
> the list will correct me.
You're correct, but I'll add some more details here.  The actual
schedule happens when needed.  A schedule may not take place at every
ms, if the task running is not done with its time slice and no events
happened where another task should preempt it. If an RT task is running
in a FIFO policy, then it will continue to run until it calls schedule
itself or another process of higher priority preempts it.
Now if you don't have PREEMPT turned on, than the schedule won't take
place at all while a task is in the kernel, unless the task explicitly
calls schedule.
What happens on a timer interrupt where a task is done with its time
slice or another event where a schedule should take place, is just the
need_resched flag is set for the task.  On return from the interrupt the
flag is checked, and if set a schedule is called.
This is still a pretty basic description of what really happens, and if
you want to learn more, just start searching the kernel code for
schedule and need_resched. Don't forget to look in the asm code (ie
entry.S, and dependent on your arch other *.S files).
-- Steve

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Re: sched /HT processor

[Arun Srinivas]

From: Steven Rostedt <[EMAIL PROTECTED]>
To: Jesper Juhl <[EMAIL PROTECTED]>
CC: Arun Srinivas <[EMAIL PROTECTED]>,LKML 

Subject: Re: sched /HT processor
Date: Sun, 03 Apr 2005 11:31:03 -0400

On Sun, 2005-04-03 at 13:17 +0200, Jesper Juhl wrote:
>
> A reschedule can happen once every ms, but also upon returning to
> userspace and when returning from an interrupt handler, and also when
> something in the kernel explicitly calls schedule() or sleeps (which in
> turn results in a call to schedule()). And each CPU runs schedule()
> independently.
> At least that's my understanding of it - if I'm wrong I hope someone on
> the list will correct me.
You're correct, but I'll add some more details here.  The actual
schedule happens when needed.  A schedule may not take place at every
ms, if the task running is not done with its time slice and no events
happened where another task should preempt it. If an RT task is running
in a FIFO policy, then it will continue to run until it calls schedule
itself or another process of higher priority preempts it.
Now if you don't have PREEMPT turned on, than the schedule won't take
place at all while a task is in the kernel, unless the task explicitly
calls schedule.
What happens on a timer interrupt where a task is done with its time
slice or another event where a schedule should take place, is just the
need_resched flag is set for the task.  On return from the interrupt the
flag is checked, and if set a schedule is called.
This is still a pretty basic description of what really happens, and if
you want to learn more, just start searching the kernel code for
schedule and need_resched. Don't forget to look in the asm code (ie
entry.S, and dependent on your arch other *.S files).
-- Steve

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Re: sched /HT processor

[Arun Srinivas]

I looked at my "include/asm-i386/param.h" and the HZ value is 1000.So, I 
suppose the timer interrupt frequency is 1000 times per sec. or once every 1 
millisec.

So, is scheduler_tick() ( for resceduling) called only once every 1 ms?? I 
am measuring the time when 2  of my processes are scheduled in a HT 
processor.So, the possible timedifference of when my 2 processes are 
scheduled can be only the following:

1) 0 (if both of my processes are scheduled @ the same time since its a HT)
2) 1ms ( this is the min. possible time diff.
3) some value greater than 1 ms
Is the above argument correct?
Thanks
From: Steven Rostedt <[EMAIL PROTECTED]>
To: Arun Srinivas <[EMAIL PROTECTED]>
CC: LKML 
Subject: Re: sched /HT processor
Date: Sat, 02 Apr 2005 20:17:54 -0500
On Sun, 2005-04-03 at 06:07 +0530, Arun Srinivas wrote:
> HI
>
> I have pentium4 hyperthreaded processor.I am using kernel 2.6.5 and i
> rebuilt my kernel with CONFIG_SMP enabled (in this kernel source there 
is
> nothing such as CONFIG_SMT...i noticed this only in recent 2.6.11).
>

I don't have a 2.6.5 available, but I do have a 2.6.9 to look at.
> 1)  So, after I rebulit it with CONFIG_SMP enabled does linux recogonize 
my
> machine as hyperthreaded or as 2 seperate processor? Also, if it does 
not
> recogonize it as hyperthreaded(but only as 2 seperate CPU's), does the
> scheduler schedule instruction in the 2 cpu's independently? (does it
> maintain 2 seperate runqueues?
>

I believe even HT on 2.6.11 maintains two different runqueues.  But it
doesn't care so much to jump from one runqueue to the next if it is HT.
> 2) If it has indeed recogonized this as hyperthreaded processor...does 
the
> scheduler use a common runqueue for the 2 logical processor?
>

No, you wouldn't want to.
> (please read below)
What do you want us to see?
> 
*
> (I am attaching the ouput of  'dmesg' (command)  on my machine)
> 
*
> Apr  2 17:43:12 kulick2 kernel: Linux version 2.6.5-1.358custom
> ([EMAIL PROTECTED]) (gcc version 3.3
> .3 20040412 (Red Hat Linux 3.3.3-7)) #133 SMP Wed Mar 30 12:16:27 CST 
2005
> Apr  2 17:43:12 kulick2 kernel: BIOS-provided physical RAM map:
> Apr  2 17:43:12 kulick2 kernel:  BIOS-e820:  -
> 000a (usable)
> Apr  2 17:43:12 kulick2 kernel:  BIOS-e820: 000f -
> 0010 (reserved)
> Apr  2 17:43:12 kulick2 kernel:  BIOS-e820: 0010 -
> 1f77 (usable)
> Apr  2 17:43:12 kulick2 kernel:  BIOS-e820: 1f77 -
> 1f772000 (ACPI NVS)
> Apr  2 17:43:12 kulick2 kernel:  BIOS-e820: 1f772000 -
> 1f793000 (ACPI data)
> Apr  2 17:43:12 kulick2 kernel:  BIOS-e820: 1f793000 -
> 1f80 (reserved)
> Apr  2 17:43:12 kulick2 kernel:  BIOS-e820: fec0 -
> fec1 (reserved)
> Apr  2 17:43:12 kulick2 kernel:  BIOS-e820: fecf -
> fecf1000 (reserved)
> Apr  2 17:43:12 kulick2 kernel:  BIOS-e820: fed2 -
> fed9 (reserved)
> Apr  2 17:43:12 kulick2 kernel:  BIOS-e820: fee0 -
> fee1 (reserved)
> Apr  2 17:43:12 kulick2 kernel:  BIOS-e820: ffb0 -
> 0001 (reserved)
> Apr  2 17:43:12 kulick2 kernel: 0MB HIGHMEM available.
> Apr  2 17:43:12 kulick2 kernel: 503MB LOWMEM available.
> Apr  2 17:43:12 kulick2 kernel: ACPI: S3 and PAE do not like each other 
for
> now, S3 disabled.
> Apr  2 17:43:12 kulick2 kernel: found SMP MP-table at 000fe710
> Apr  2 17:43:12 kulick2 kernel: On node 0 totalpages: 128880
> Apr  2 17:43:12 kulick2 kernel:   DMA zone: 4096 pages, LIFO batch:1
> Apr  2 17:43:12 kulick2 kernel:   Normal zone: 124784 pages, LIFO 
batch:16
> Apr  2 17:43:12 kulick2 kernel:   HighMem zone: 0 pages, LIFO batch:1
> Apr  2 17:43:12 kulick2 kernel: DMI 2.3 present.
> Apr  2 17:43:12 kulick2 kernel: Using APIC driver default
> Apr  2 17:43:12 kulick2 kernel: ACPI: RSDP (v000 DELL
>) @
> 0x000feba0
> Apr  2 17:43:12 kulick2 kernel: ACPI: RSDT (v001 DELLGX270   
0x0007
> ASL  0x0061) @
> 0x000fd192
> Apr  2 17:43:12 kulick2 kernel: ACPI: FADT (v001 DELLGX270   
0x0007
> ASL  0x0061) @
> 0x000fd1ca
> Apr  2 17:43:12 kulick2 kernel: ACPI: SSDT (v001   DELLst_ex 
0x1000
> MSFT 0x010d) @
> 0xfffd4eee
> Apr  2 17:43:12 kulick2 irqbalance: irqbalance startup succeeded
> Apr  2 17:43:12 kulick2 kernel: ACPI: MADT (v001 DELLGX270   
0x0007
> ASL  0x0061) @
> 0x000fd23e
> Apr  2 17:43:12 kulick2 kernel: A

setting cpu affinity-help

[Arun Srinivas]

hi
can someone show me an example usage of sched_setaffinity().I do not know 
how to set the affinity mask for a process.please.

thanks
arun
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Re: sched /HT processor

[Arun Srinivas]

I attached the 'dmesg' output because there it shows that my kernel 
recogonized 2 cpu's.As said earlier , are they treated as 2 physical cpu's 
or logical cpu's?

From: Steven Rostedt <[EMAIL PROTECTED]>
To: Arun Srinivas <[EMAIL PROTECTED]>
CC: LKML 
Subject: Re: sched /HT processor
Date: Sat, 02 Apr 2005 20:17:54 -0500
On Sun, 2005-04-03 at 06:07 +0530, Arun Srinivas wrote:
> HI
>
> I have pentium4 hyperthreaded processor.I am using kernel 2.6.5 and i
> rebuilt my kernel with CONFIG_SMP enabled (in this kernel source there 
is
> nothing such as CONFIG_SMT...i noticed this only in recent 2.6.11).
>

I don't have a 2.6.5 available, but I do have a 2.6.9 to look at.
> 1)  So, after I rebulit it with CONFIG_SMP enabled does linux recogonize 
my
> machine as hyperthreaded or as 2 seperate processor? Also, if it does 
not
> recogonize it as hyperthreaded(but only as 2 seperate CPU's), does the
> scheduler schedule instruction in the 2 cpu's independently? (does it
> maintain 2 seperate runqueues?
>

I believe even HT on 2.6.11 maintains two different runqueues.  But it
doesn't care so much to jump from one runqueue to the next if it is HT.
> 2) If it has indeed recogonized this as hyperthreaded processor...does 
the
> scheduler use a common runqueue for the 2 logical processor?
>

No, you wouldn't want to.
> (please read below)
What do you want us to see?
> 
*
> (I am attaching the ouput of  'dmesg' (command)  on my machine)
> 
*
> Apr  2 17:43:12 kulick2 kernel: Linux version 2.6.5-1.358custom
> ([EMAIL PROTECTED]) (gcc version 3.3
> .3 20040412 (Red Hat Linux 3.3.3-7)) #133 SMP Wed Mar 30 12:16:27 CST 
2005
> Apr  2 17:43:12 kulick2 kernel: BIOS-provided physical RAM map:
> Apr  2 17:43:12 kulick2 kernel:  BIOS-e820:  -
> 000a (usable)
> Apr  2 17:43:12 kulick2 kernel:  BIOS-e820: 000f -
> 0010 (reserved)
> Apr  2 17:43:12 kulick2 kernel:  BIOS-e820: 0010 -
> 1f77 (usable)
> Apr  2 17:43:12 kulick2 kernel:  BIOS-e820: 1f77 -
> 1f772000 (ACPI NVS)
> Apr  2 17:43:12 kulick2 kernel:  BIOS-e820: 1f772000 -
> 1f793000 (ACPI data)
> Apr  2 17:43:12 kulick2 kernel:  BIOS-e820: 1f793000 -
> 1f80 (reserved)
> Apr  2 17:43:12 kulick2 kernel:  BIOS-e820: fec0 -
> fec1 (reserved)
> Apr  2 17:43:12 kulick2 kernel:  BIOS-e820: fecf -
> fecf1000 (reserved)
> Apr  2 17:43:12 kulick2 kernel:  BIOS-e820: fed2 -
> fed9 (reserved)
> Apr  2 17:43:12 kulick2 kernel:  BIOS-e820: fee0 -
> fee1 (reserved)
> Apr  2 17:43:12 kulick2 kernel:  BIOS-e820: ffb0 -
> 0001 (reserved)
> Apr  2 17:43:12 kulick2 kernel: 0MB HIGHMEM available.
> Apr  2 17:43:12 kulick2 kernel: 503MB LOWMEM available.
> Apr  2 17:43:12 kulick2 kernel: ACPI: S3 and PAE do not like each other 
for
> now, S3 disabled.
> Apr  2 17:43:12 kulick2 kernel: found SMP MP-table at 000fe710
> Apr  2 17:43:12 kulick2 kernel: On node 0 totalpages: 128880
> Apr  2 17:43:12 kulick2 kernel:   DMA zone: 4096 pages, LIFO batch:1
> Apr  2 17:43:12 kulick2 kernel:   Normal zone: 124784 pages, LIFO 
batch:16
> Apr  2 17:43:12 kulick2 kernel:   HighMem zone: 0 pages, LIFO batch:1
> Apr  2 17:43:12 kulick2 kernel: DMI 2.3 present.
> Apr  2 17:43:12 kulick2 kernel: Using APIC driver default
> Apr  2 17:43:12 kulick2 kernel: ACPI: RSDP (v000 DELL
>) @
> 0x000feba0
> Apr  2 17:43:12 kulick2 kernel: ACPI: RSDT (v001 DELLGX270   
0x0007
> ASL  0x0061) @
> 0x000fd192
> Apr  2 17:43:12 kulick2 kernel: ACPI: FADT (v001 DELLGX270   
0x0007
> ASL  0x0061) @
> 0x000fd1ca
> Apr  2 17:43:12 kulick2 kernel: ACPI: SSDT (v001   DELLst_ex 
0x1000
> MSFT 0x010d) @
> 0xfffd4eee
> Apr  2 17:43:12 kulick2 irqbalance: irqbalance startup succeeded
> Apr  2 17:43:12 kulick2 kernel: ACPI: MADT (v001 DELLGX270   
0x0007
> ASL  0x0061) @
> 0x000fd23e
> Apr  2 17:43:12 kulick2 kernel: ACPI: BOOT (v001 DELLGX270   
0x0007
> ASL  0x0061) @
> 0x000fd2aa
> Apr  2 17:43:12 kulick2 kernel: ACPI: ASF! (v016 DELLGX270   
0x0007
> ASL  0x0061) @
> 0x000fd2d2
> Apr  2 17:43:12 kulick2 kernel: ACPI: DSDT (v001   DELLdt_ex 
0x1000
> MSFT 0x010d) @
> 0x
> Apr  2 17:43:12 kulick2 kernel: ACPI: PM-Timer IO Port: 0x808
> Apr  2 17:43:12 kulick2 kernel: AC

sched /HT processor

[Arun Srinivas]

HI
I have pentium4 hyperthreaded processor.I am using kernel 2.6.5 and i 
rebuilt my kernel with CONFIG_SMP enabled (in this kernel source there is 
nothing such as CONFIG_SMT...i noticed this only in recent 2.6.11).

1)  So, after I rebulit it with CONFIG_SMP enabled does linux recogonize my 
machine as hyperthreaded or as 2 seperate processor? Also, if it does not 
recogonize it as hyperthreaded(but only as 2 seperate CPU's), does the 
scheduler schedule instruction in the 2 cpu's independently? (does it 
maintain 2 seperate runqueues?

2) If it has indeed recogonized this as hyperthreaded processor...does the 
scheduler use a common runqueue for the 2 logical processor?

(please read below)
*
(I am attaching the ouput of  'dmesg' (command)  on my machine)
*
Apr  2 17:43:12 kulick2 kernel: Linux version 2.6.5-1.358custom 
([EMAIL PROTECTED]) (gcc version 3.3
.3 20040412 (Red Hat Linux 3.3.3-7)) #133 SMP Wed Mar 30 12:16:27 CST 2005
Apr  2 17:43:12 kulick2 kernel: BIOS-provided physical RAM map:
Apr  2 17:43:12 kulick2 kernel:  BIOS-e820:  - 
000a (usable)
Apr  2 17:43:12 kulick2 kernel:  BIOS-e820: 000f - 
0010 (reserved)
Apr  2 17:43:12 kulick2 kernel:  BIOS-e820: 0010 - 
1f77 (usable)
Apr  2 17:43:12 kulick2 kernel:  BIOS-e820: 1f77 - 
1f772000 (ACPI NVS)
Apr  2 17:43:12 kulick2 kernel:  BIOS-e820: 1f772000 - 
1f793000 (ACPI data)
Apr  2 17:43:12 kulick2 kernel:  BIOS-e820: 1f793000 - 
1f80 (reserved)
Apr  2 17:43:12 kulick2 kernel:  BIOS-e820: fec0 - 
fec1 (reserved)
Apr  2 17:43:12 kulick2 kernel:  BIOS-e820: fecf - 
fecf1000 (reserved)
Apr  2 17:43:12 kulick2 kernel:  BIOS-e820: fed2 - 
fed9 (reserved)
Apr  2 17:43:12 kulick2 kernel:  BIOS-e820: fee0 - 
fee1 (reserved)
Apr  2 17:43:12 kulick2 kernel:  BIOS-e820: ffb0 - 
0001 (reserved)
Apr  2 17:43:12 kulick2 kernel: 0MB HIGHMEM available.
Apr  2 17:43:12 kulick2 kernel: 503MB LOWMEM available.
Apr  2 17:43:12 kulick2 kernel: ACPI: S3 and PAE do not like each other for 
now, S3 disabled.
Apr  2 17:43:12 kulick2 kernel: found SMP MP-table at 000fe710
Apr  2 17:43:12 kulick2 kernel: On node 0 totalpages: 128880
Apr  2 17:43:12 kulick2 kernel:   DMA zone: 4096 pages, LIFO batch:1
Apr  2 17:43:12 kulick2 kernel:   Normal zone: 124784 pages, LIFO batch:16
Apr  2 17:43:12 kulick2 kernel:   HighMem zone: 0 pages, LIFO batch:1
Apr  2 17:43:12 kulick2 kernel: DMI 2.3 present.
Apr  2 17:43:12 kulick2 kernel: Using APIC driver default
Apr  2 17:43:12 kulick2 kernel: ACPI: RSDP (v000 DELL
  ) @
0x000feba0
Apr  2 17:43:12 kulick2 kernel: ACPI: RSDT (v001 DELLGX270   0x0007 
ASL  0x0061) @
0x000fd192
Apr  2 17:43:12 kulick2 kernel: ACPI: FADT (v001 DELLGX270   0x0007 
ASL  0x0061) @
0x000fd1ca
Apr  2 17:43:12 kulick2 kernel: ACPI: SSDT (v001   DELLst_ex 0x1000 
MSFT 0x010d) @
0xfffd4eee
Apr  2 17:43:12 kulick2 irqbalance: irqbalance startup succeeded
Apr  2 17:43:12 kulick2 kernel: ACPI: MADT (v001 DELLGX270   0x0007 
ASL  0x0061) @
0x000fd23e
Apr  2 17:43:12 kulick2 kernel: ACPI: BOOT (v001 DELLGX270   0x0007 
ASL  0x0061) @
0x000fd2aa
Apr  2 17:43:12 kulick2 kernel: ACPI: ASF! (v016 DELLGX270   0x0007 
ASL  0x0061) @
0x000fd2d2
Apr  2 17:43:12 kulick2 kernel: ACPI: DSDT (v001   DELLdt_ex 0x1000 
MSFT 0x010d) @
0x
Apr  2 17:43:12 kulick2 kernel: ACPI: PM-Timer IO Port: 0x808
Apr  2 17:43:12 kulick2 kernel: ACPI: LAPIC (acpi_id[0x01] lapic_id[0x00] 
enabled)
Apr  2 17:43:12 kulick2 kernel: Processor #0 15:2 APIC version 20
Apr  2 17:43:12 kulick2 kernel: ACPI: LAPIC (acpi_id[0x02] lapic_id[0x01] 
enabled)
Apr  2 17:43:12 kulick2 kernel: Processor #1 15:2 APIC version 20
Apr  2 17:43:12 kulick2 kernel: ACPI: LAPIC (acpi_id[0x03] lapic_id[0x01] 
disabled)
Apr  2 17:43:12 kulick2 kernel: ACPI: LAPIC (acpi_id[0x04] lapic_id[0x03] 
disabled)
Apr  2 17:43:12 kulick2 kernel: ACPI: IOAPIC (id[0x02] address[0xfec0] 
global_irq_base[0x0]
)
Apr  2 17:43:12 kulick2 kernel: IOAPIC[0]: Assigned apic_id 2
Apr  2 17:43:12 kulick2 kernel: IOAPIC[0]: apic_id 2, version 32, address 
0xfec0, GSI 0-23
Apr  2 17:43:12 kulick2 kernel: ACPI: INT_SRC_OVR (bus 0 bus_irq 0 
global_irq 2 dfl dfl)
Apr  2 17:43:12 kulick2 kernel: ACPI: INT_SRC_OVR (bus 0 bus_irq 9 
global_irq 9 high level)
Apr  2 17:43:12 kulick2 kernel: Enabling APIC mode:  Flat.  Using 1 I/O 
APICs
Apr  2 17:43:12 kulick2 kernel: Using ACPI (MADT) for SMP configuration 
information
Apr  2 17:43:12 kulick2 portmap: portmap startup succeeded

Re: sched_setscheduler() and usage issues ....please help

[Arun Srinivas]

When I schedule my process with SCHED_FIFO policy (using 
sched_setscheduler()) , is there any means to verify that it is indeed being 
scheduled with the same priority?

thanks
arun
From: Steven Rostedt <[EMAIL PROTECTED]>
To: Arun Srinivas <[EMAIL PROTECTED]>
Subject: Re: sched_setscheduler() and usage issues please help
Date: Tue, 29 Mar 2005 06:31:43 -0500
On Tue, 2005-03-29 at 13:25 +0530, Arun Srinivas wrote:
> thanks.gcc says "could not find strutils.h". I am using kernel 2.6.x 
with
> gcc 3.3.4. Where can I find the file?

Oops! Sorry, I gave you a modified version of my actual program. I have
my own usage wrapper, that I use in all my tools. I took it out, but
forgot about my header. That is a custom header, just take it out and it
will compile.
OK, just to be clean, I've attached it here.
-- Steve
<< setscheduler.c >>
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sched_setscheduler() and usage issues ....please help

[Arun Srinivas]

I am trying to set the SCHED_FIFO  policy for my process.I am using 
sched_setscheduler() function to do this.

I am following the correct syntax and running it as root process.I am using 
the given syntax i.e.,
int sched_setscheduler(pid_t pid, int policy, const struct sched_param *p);
(SCHED_FIFO for the policy and priority in the range of 1 to 99 for p).

But the function returns with an value of -1. I am trying to call this 
function from the user-space.

1) Is this usage correct?
2)How do I read the error code (i.e., text description of what kiind of 
error occurred like for eg., ESRCH,EPERM,EINVAL).

Please help.
thanks
Arun
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Re: help needed pls. scheduler(kernel 2.6) + hyperthreaded related questions?

[Arun Srinivas]

few more trivial Q's (bear with me  I'm a newbie to kernel world):
1) As I said I have a process that spawns 2 threads(thread A and B).I am 
trying to measure the exact time @ which they are being scheduled.For this I 
am using the rdtsc() (when threads A and B come)  in enqueue_task()..where 
they are being inserted into the priority array.
Is this a correct way of measuring?

2) also in task_struct.is "tgid" the id of my process and each of 
threads hav a unique pid??

3) I saw frm the kernel docs tht realtime tasks hav priority 0 to 99. So 
using setscheduler means do I have to enforce a priority in one of these 
ranges to make my threads as soft/hard realtime task.

thanks in advance for your patience.
From: Nick Piggin <[EMAIL PROTECTED]>
To: Arun Srinivas <[EMAIL PROTECTED]>
CC: linux-kernel@vger.kernel.org
Subject: Re: help needed pls. scheduler(kernel 2.6) + hyperthreaded related 
questions?
Date: Wed, 23 Mar 2005 18:37:16 +1100

Arun Srinivas wrote:
If the SMT (apart from SMP) support is enabled in the  .config file, does 
the kernel recogonize the 2 logical processor as 2 logical or 2 physical 
processors?

You shouldn't be able to select SMT if SMP is not enabled.
If SMT and SMP is selected, then the scheduler will recognise
the 2 processors as logical ones.
Also, as the hyperthreaded processor may schedule 2 threads in the 2 
logical cpu's, and it may not necessarily be form the same process i.e., 
the 2 thread it schedules may be from the same or from the different 
process.

Yes.
So, is there any way I can tell the scheduler (assuming I make the 
scheduler recogonize my 2 threads..i.e., it knows their pid) to schedule 
always my 2 threads @ the same time? How do I go abt it?

Use sched_setaffinity to force each thread onto the particular
CPU. Use sched_setscheduler to acquire a realtime scheduling
policy. Then use mutexes to synchronise your threads so they
run the desired code segment at the same time.
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Re: help needed pls. scheduler(kernel 2.6) + hyperthreaded related questions?

[Arun Srinivas]

If the SMT (apart from SMP) support is enabled in the  .config file, does 
the kernel recogonize the 2 logical processor as 2 logical or 2 physical 
processors?

Also, as the hyperthreaded processor may schedule 2 threads in the 2 logical 
cpu's, and it may not necessarily be form the same process i.e., the 2 
thread it schedules may be from the same or from the different process.

So, is there any way I can tell the scheduler (assuming I make the scheduler 
recogonize my 2 threads..i.e., it knows their pid) to schedule always my 2 
threads @ the same time? How do I go abt it?

Pls. help.Thanks in Advance.
From: Nick Piggin <[EMAIL PROTECTED]>
To: Arun Srinivas <[EMAIL PROTECTED]>
CC: linux-kernel@vger.kernel.org
Subject: Re: help needed pls. scheduler(kernel 2.6) + hyperthreaded related 
questions?
Date: Wed, 23 Mar 2005 10:16:20 +1100

Arun Srinivas wrote:
Pls. help me.  I went through the sched.c for kernel 2.6 and saw that it 
supports
hyperthreading.I would be glad if someone could answer this 
question(if
am not wrong a HT processor has 2 architectural states and one execution
unit...i.e., two pipeline streams)

1)when there are 2 processes a parent and child(created by fork()) do they
get scheduled @ the same time...ie., when the parent process is put into 
one
pipeline, do the child also gets scheduled the same time?

No.
2) what abt in the case of threads(I read tht as opposed to 
kernel2.4,where
threads are treated as processes) ..kernel 2.6 treats threads as threads.
So, when two paired threads get into execution are they always scheduled 
at
the same time?

No.
Also, it would be helpful if someone could suggest which part of sched.c
shud i look into to find out how threads are scheduled for a normal
processor and for a hyperthreaded processor
It is pretty tricky. Basically processes on different CPUs are
scheduled completely independently of one another. The only time
when they may get moved from one CPU to another is with
load_balance, load_balance_newidle, active_load_balance,
try_to_wake_up, sched_exec, wake_up_new_task.
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help needed pls. scheduler(kernel 2.6) + hyperthreaded related questions?

[Arun Srinivas]

Pls. help me.  I went through the sched.c for kernel 2.6 and saw that it 
supports
hyperthreading.I would be glad if someone could answer this question(if
am not wrong a HT processor has 2 architectural states and one execution
unit...i.e., two pipeline streams)

1)when there are 2 processes a parent and child(created by fork()) do they
get scheduled @ the same time...ie., when the parent process is put into one
pipeline, do the child also gets scheduled the same time?
2) what abt in the case of threads(I read tht as opposed to kernel2.4,where
threads are treated as processes) ..kernel 2.6 treats threads as threads.
So, when two paired threads get into execution are they always scheduled at
the same time?
Also, it would be helpful if someone could suggest which part of sched.c
shud i look into to find out how threads are scheduled for a normal
processor and for a hyperthreaded processor
Pls. CC your replies to this email address [EMAIL PROTECTED]
Thanks
Arun
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Please read the FAQ at  http://www.tux.org/lkml/

scheduler(kernel 2.6) + hyperthreaded related questions?

[Arun Srinivas]

I went through the sched.c for kernel 2.6 and saw that it supports 
hyperthreading.I would be glad if someone could answer this question(if 
am not wrong a HT processor has 2 architectural states and one execution 
unit...i.e., two pipeline streams)

1)when there are 2 processes a parent and child(created by fork()) do they 
get scheduled @ the same time...ie., when the parent process is put into one 
pipeline, do the child also gets scheduled the same time?

2) what abt in the case of threads(I read tht as opposed to kernel2.4,where 
threads are treated as processes) ..kernel 2.6 treats threads as threads. 
So, when two paired threads get into execution are they always scheduled at 
the same time?

Also, it would be helpful if someone could suggest which part of sched.c 
shud i look into to find out how threads are scheduled for a normal 
processor and for a hyperthreaded processor

Pls. CC your replies to this email address [EMAIL PROTECTED]
Thanks
Arun
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