[PATCH] nohz: ensure users are aware boot CPU is not NO_HZ_FULL

[PATCH] nohz: ensure users are aware boot CPU is not NO_HZ_FULL

[Paul Gortmaker]

This bit of information is in the Kconfig help text:

  Note the boot CPU will still be kept outside the range to
  handle the timekeeping duty.

However neither the variable NO_HZ_FULL_ALL, or the prompt
convey this important detail, so lets add it to the prompt
to make it more explicitly obvious to the average user.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
---
 kernel/time/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig
index 3ce6e8c5f3fc..76a1fbef1fd8 100644
--- a/kernel/time/Kconfig
+++ b/kernel/time/Kconfig
@@ -124,7 +124,7 @@ config NO_HZ_FULL
 endchoice
 
 config NO_HZ_FULL_ALL
-       bool "Full dynticks system on all CPUs by default"
+       bool "Full dynticks system on all (but boot) CPUs by default"
        depends on NO_HZ_FULL
        help
          If the user doesn't pass the nohz_full boot option to
-- 
1.8.5.2

Re: [PATCH] nohz: ensure users are aware boot CPU is not NO_HZ_FULL

[Paul E. McKenney]

On Tue, Jan 28, 2014 at 12:10:49PM -0500, Paul Gortmaker wrote:
> This bit of information is in the Kconfig help text:
> 
>   Note the boot CPU will still be kept outside the range to
>   handle the timekeeping duty.
> 
> However neither the variable NO_HZ_FULL_ALL, or the prompt
> convey this important detail, so lets add it to the prompt
> to make it more explicitly obvious to the average user.
> 
> Cc: Frederic Weisbecker <fweisbec@gmail.com>
> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
> Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

> ---
>  kernel/time/Kconfig | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig
> index 3ce6e8c5f3fc..76a1fbef1fd8 100644
> --- a/kernel/time/Kconfig
> +++ b/kernel/time/Kconfig
> @@ -124,7 +124,7 @@ config NO_HZ_FULL
>  endchoice
> 
>  config NO_HZ_FULL_ALL
> -       bool "Full dynticks system on all CPUs by default"
> +       bool "Full dynticks system on all (but boot) CPUs by default"
>         depends on NO_HZ_FULL
>         help
>           If the user doesn't pass the nohz_full boot option to
> -- 
> 1.8.5.2
> 

Re: [PATCH] nohz: ensure users are aware boot CPU is not NO_HZ_FULL

[Frederic Weisbecker]

On Tue, Jan 28, 2014 at 04:06:30PM -0800, Paul E. McKenney wrote:
> On Tue, Jan 28, 2014 at 12:10:49PM -0500, Paul Gortmaker wrote:
> > This bit of information is in the Kconfig help text:
> > 
> >   Note the boot CPU will still be kept outside the range to
> >   handle the timekeeping duty.
> > 
> > However neither the variable NO_HZ_FULL_ALL, or the prompt
> > convey this important detail, so lets add it to the prompt
> > to make it more explicitly obvious to the average user.
> > 
> > Cc: Frederic Weisbecker <fweisbec@gmail.com>
> > Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
> > Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
> 
> Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> 
> > ---
> >  kernel/time/Kconfig | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig
> > index 3ce6e8c5f3fc..76a1fbef1fd8 100644
> > --- a/kernel/time/Kconfig
> > +++ b/kernel/time/Kconfig
> > @@ -124,7 +124,7 @@ config NO_HZ_FULL
> >  endchoice
> > 
> >  config NO_HZ_FULL_ALL
> > -       bool "Full dynticks system on all CPUs by default"
> > +       bool "Full dynticks system on all (but boot) CPUs by default"

Looks good. Now we are all using "boot CPU" to refer to the CPU 0, but it may
not sound that obvious to everyone.

How about: "Full dynticks system on all CPUs by default (expect CPU 0)" ?

Sure this is a temporary behaviour until I get the sysidle detection use patchset in shape,
but indeed worth a big fat warning until we sort it out.

Thanks!

> >         depends on NO_HZ_FULL
> >         help
> >           If the user doesn't pass the nohz_full boot option to
> > -- 
> > 1.8.5.2
> > 
> 

Re: [PATCH] nohz: ensure users are aware boot CPU is not NO_HZ_FULL

[Paul Gortmaker]

On 14-01-31 11:38 AM, Frederic Weisbecker wrote:
> On Tue, Jan 28, 2014 at 04:06:30PM -0800, Paul E. McKenney wrote:
>> On Tue, Jan 28, 2014 at 12:10:49PM -0500, Paul Gortmaker wrote:
>>> This bit of information is in the Kconfig help text:
>>>
>>>   Note the boot CPU will still be kept outside the range to
>>>   handle the timekeeping duty.
>>>
>>> However neither the variable NO_HZ_FULL_ALL, or the prompt
>>> convey this important detail, so lets add it to the prompt
>>> to make it more explicitly obvious to the average user.
>>>
>>> Cc: Frederic Weisbecker <fweisbec@gmail.com>
>>> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
>>> Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
>>
>> Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
>>
>>> ---
>>>  kernel/time/Kconfig | 2 +-
>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig
>>> index 3ce6e8c5f3fc..76a1fbef1fd8 100644
>>> --- a/kernel/time/Kconfig
>>> +++ b/kernel/time/Kconfig
>>> @@ -124,7 +124,7 @@ config NO_HZ_FULL
>>>  endchoice
>>>
>>>  config NO_HZ_FULL_ALL
>>> -       bool "Full dynticks system on all CPUs by default"
>>> +       bool "Full dynticks system on all (but boot) CPUs by default"
> 
> Looks good. Now we are all using "boot CPU" to refer to the CPU 0, but it may
> not sound that obvious to everyone.
> 
> How about: "Full dynticks system on all CPUs by default (expect CPU 0)" ?

Sure, I'll send a v2 with the above, but I'll s/expect/except/   :)

Thanks,
Paul.
--

> 
> Sure this is a temporary behaviour until I get the sysidle detection use patchset in shape,
> but indeed worth a big fat warning until we sort it out.
> 
> Thanks!
> 
>>>         depends on NO_HZ_FULL
>>>         help
>>>           If the user doesn't pass the nohz_full boot option to
>>> -- 
>>> 1.8.5.2
>>>
>>

[PATCH v2] nohz: ensure users are aware boot CPU is not NO_HZ_FULL

[Paul Gortmaker]

This bit of information is in the Kconfig help text:

  Note the boot CPU will still be kept outside the range to
  handle the timekeeping duty.

However neither the variable NO_HZ_FULL_ALL, or the prompt
convey this important detail, so lets add it to the prompt
to make it more explicitly obvious to the average user.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
---

v2: use "CPU 0" instead of "boot CPU".

 kernel/time/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig
index 3ce6e8c5f3fc..f448513a45ed 100644
--- a/kernel/time/Kconfig
+++ b/kernel/time/Kconfig
@@ -124,7 +124,7 @@ config NO_HZ_FULL
 endchoice
 
 config NO_HZ_FULL_ALL
-       bool "Full dynticks system on all CPUs by default"
+       bool "Full dynticks system on all CPUs by default (except CPU 0)"
        depends on NO_HZ_FULL
        help
          If the user doesn't pass the nohz_full boot option to
-- 
1.8.5.2

Re: [PATCH v2] nohz: ensure users are aware boot CPU is not NO_HZ_FULL

[Frederic Weisbecker]

On Thu, Feb 06, 2014 at 01:36:21PM -0500, Paul Gortmaker wrote:
> This bit of information is in the Kconfig help text:
> 
>   Note the boot CPU will still be kept outside the range to
>   handle the timekeeping duty.
> 
> However neither the variable NO_HZ_FULL_ALL, or the prompt
> convey this important detail, so lets add it to the prompt
> to make it more explicitly obvious to the average user.
> 
> Cc: Frederic Weisbecker <fweisbec@gmail.com>
> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>

Paul, I guess I can keep your ack on this 2nd version?

> Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

Applied, thanks a lot!

> ---
> 
> v2: use "CPU 0" instead of "boot CPU".
> 
>  kernel/time/Kconfig | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig
> index 3ce6e8c5f3fc..f448513a45ed 100644
> --- a/kernel/time/Kconfig
> +++ b/kernel/time/Kconfig
> @@ -124,7 +124,7 @@ config NO_HZ_FULL
>  endchoice
>  
>  config NO_HZ_FULL_ALL
> -       bool "Full dynticks system on all CPUs by default"
> +       bool "Full dynticks system on all CPUs by default (except CPU 0)"
>         depends on NO_HZ_FULL
>         help
>           If the user doesn't pass the nohz_full boot option to
> -- 
> 1.8.5.2
> 
> --
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Re: [PATCH v2] nohz: ensure users are aware boot CPU is not NO_HZ_FULL

[Paul E. McKenney]

On Mon, Feb 10, 2014 at 05:19:34PM +0100, Frederic Weisbecker wrote:
> On Thu, Feb 06, 2014 at 01:36:21PM -0500, Paul Gortmaker wrote:
> > This bit of information is in the Kconfig help text:
> > 
> >   Note the boot CPU will still be kept outside the range to
> >   handle the timekeeping duty.
> > 
> > However neither the variable NO_HZ_FULL_ALL, or the prompt
> > convey this important detail, so lets add it to the prompt
> > to make it more explicitly obvious to the average user.
> > 
> > Cc: Frederic Weisbecker <fweisbec@gmail.com>
> > Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
> 
> Paul, I guess I can keep your ack on this 2nd version?

Please do!

						Thanx, Paul

> > Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
> 
> Applied, thanks a lot!
> 
> > ---
> > 
> > v2: use "CPU 0" instead of "boot CPU".
> > 
> >  kernel/time/Kconfig | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig
> > index 3ce6e8c5f3fc..f448513a45ed 100644
> > --- a/kernel/time/Kconfig
> > +++ b/kernel/time/Kconfig
> > @@ -124,7 +124,7 @@ config NO_HZ_FULL
> >  endchoice
> >  
> >  config NO_HZ_FULL_ALL
> > -       bool "Full dynticks system on all CPUs by default"
> > +       bool "Full dynticks system on all CPUs by default (except CPU 0)"
> >         depends on NO_HZ_FULL
> >         help
> >           If the user doesn't pass the nohz_full boot option to
> > -- 
> > 1.8.5.2
> > 
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > Please read the FAQ at  http://www.tux.org/lkml/
> 

[tip:timers/core] nohz: ensure users are aware boot CPU is not NO_HZ_FULL

[tip-bot for Paul Gortmaker]

Commit-ID:  f96a34e27df19335155394a235ea3a096bc52a71
Gitweb:     http://git.kernel.org/tip/f96a34e27df19335155394a235ea3a096bc52a71
Author:     Paul Gortmaker <paul.gortmaker@windriver.com>
AuthorDate: Thu, 6 Feb 2014 13:36:21 -0500
Committer:  Frederic Weisbecker <fweisbec@gmail.com>
CommitDate: Fri, 14 Feb 2014 17:59:17 +0100

nohz: ensure users are aware boot CPU is not NO_HZ_FULL

This bit of information is in the Kconfig help text:

  "Note the boot CPU will still be kept outside the range to
  handle the timekeeping duty."

However neither the variable NO_HZ_FULL_ALL, or the prompt
convey this important detail, so lets add it to the prompt
to make it more explicitly obvious to the average user.

Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1391711781-7466-1-git-send-email-paul.gortmaker@windriver.com
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
---
 kernel/time/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig
index 3ce6e8c..f448513 100644
--- a/kernel/time/Kconfig
+++ b/kernel/time/Kconfig
@@ -124,7 +124,7 @@ config NO_HZ_FULL
 endchoice
 
 config NO_HZ_FULL_ALL
-       bool "Full dynticks system on all CPUs by default"
+       bool "Full dynticks system on all CPUs by default (except CPU 0)"
        depends on NO_HZ_FULL
        help
          If the user doesn't pass the nohz_full boot option to