[PATCH] Documentation: admin-guide: pm: cpufreq: fix sampling_rate example command

[PATCH] Documentation: admin-guide: pm: cpufreq: fix sampling_rate example command

[wangxiaodong]

The example shell command for setting ondemand's sampling_rate wraps an
arithmetic expansion $((...)) in command-substitution backticks. The
arithmetic result is then executed as a command, which fails and writes
an empty value. Drop the surrounding backticks so the computed value is
passed to echo as intended.

Signed-off-by: wangxiaodong <wangxiaodong827546786@gmail.com>
---
 Documentation/admin-guide/pm/cpufreq.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Documentation/admin-guide/pm/cpufreq.rst b/Documentation/admin-guide/pm/cpufreq.rst
index 8831cface585..34baf20cc202 100644
--- a/Documentation/admin-guide/pm/cpufreq.rst
+++ b/Documentation/admin-guide/pm/cpufreq.rst
@@ -497,7 +497,7 @@ This governor exposes the following tunables:
 	represented by it to be 1.5 times as high as the transition latency
 	(the default)::
 
-	# echo `$(($(cat cpuinfo_transition_latency) * 3 / 2))` > ondemand/sampling_rate
+	# echo $(($(cat cpuinfo_transition_latency) * 3 / 2)) > ondemand/sampling_rate
 
 ``up_threshold``
 	If the estimated CPU load is above this value (in percent), the governor
-- 
2.43.0

Re: [PATCH] Documentation: admin-guide: pm: cpufreq: fix sampling_rate example command

[Randy Dunlap]

On 6/20/26 7:25 PM, wangxiaodong wrote:
> The example shell command for setting ondemand's sampling_rate wraps an
> arithmetic expansion $((...)) in command-substitution backticks. The
> arithmetic result is then executed as a command, which fails and writes
> an empty value. Drop the surrounding backticks so the computed value is
> passed to echo as intended.
> 
> Signed-off-by: wangxiaodong <wangxiaodong827546786@gmail.com>
> ---
>  Documentation/admin-guide/pm/cpufreq.rst | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/Documentation/admin-guide/pm/cpufreq.rst b/Documentation/admin-guide/pm/cpufreq.rst
> index 8831cface585..34baf20cc202 100644
> --- a/Documentation/admin-guide/pm/cpufreq.rst
> +++ b/Documentation/admin-guide/pm/cpufreq.rst
> @@ -497,7 +497,7 @@ This governor exposes the following tunables:
>  	represented by it to be 1.5 times as high as the transition latency
>  	(the default)::
>  
> -	# echo `$(($(cat cpuinfo_transition_latency) * 3 / 2))` > ondemand/sampling_rate
> +	# echo $(($(cat cpuinfo_transition_latency) * 3 / 2)) > ondemand/sampling_rate

Ugh. Thanks.
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>

and possibly:
Fixes: e54ac586674d ("cpufreq: editing corrections to cpufreq.rst")

>  
>  ``up_threshold``
>  	If the estimated CPU load is above this value (in percent), the governor

-- 
~Randy

Re: [PATCH] Documentation: admin-guide: pm: cpufreq: fix sampling_rate example command

[Zhongqiu Han]

On 6/21/2026 11:52 AM, Randy Dunlap wrote:
> 
> 
> On 6/20/26 7:25 PM, wangxiaodong wrote:
>> The example shell command for setting ondemand's sampling_rate wraps an
>> arithmetic expansion $((...)) in command-substitution backticks. The
>> arithmetic result is then executed as a command, which fails and writes
>> an empty value. Drop the surrounding backticks so the computed value is
>> passed to echo as intended.
>>
>> Signed-off-by: wangxiaodong <wangxiaodong827546786@gmail.com>
>> ---
>>   Documentation/admin-guide/pm/cpufreq.rst | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/Documentation/admin-guide/pm/cpufreq.rst b/Documentation/admin-guide/pm/cpufreq.rst
>> index 8831cface585..34baf20cc202 100644
>> --- a/Documentation/admin-guide/pm/cpufreq.rst
>> +++ b/Documentation/admin-guide/pm/cpufreq.rst
>> @@ -497,7 +497,7 @@ This governor exposes the following tunables:
>>   	represented by it to be 1.5 times as high as the transition latency
>>   	(the default)::
>>   
>> -	# echo `$(($(cat cpuinfo_transition_latency) * 3 / 2))` > ondemand/sampling_rate
>> +	# echo $(($(cat cpuinfo_transition_latency) * 3 / 2)) > ondemand/sampling_rate
> 
> Ugh. Thanks.
> Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
> 
> and possibly:
> Fixes: e54ac586674d ("cpufreq: editing corrections to cpufreq.rst")


Thanks Randy,

Just to back up Randy's Fixes suggestion, the line evolved as follows
(most recent first):

2025/04/04 e54ac586674d:  #echo `$((.. * 3 / 2))` >  (trailing ` added)
2024/10/17 29dcbea92460:  #echo `$((.. * 3 / 2))  >  (still dangling `)
2017/03/13 2a0e49279850:  #echo `$((.. * 750 / 1000)) > (dangling leading `)

The stray backtick can be traced back to 2a0e49279850, but it was just a
dangling backtick then. The closed command-substitution form fixed here
was only reached after e54ac586674d added the trailing backtick. Note
that the "750/1000 -> 3/2" change in 29dcbea92460 was not just a doc
edit: it reflects an actual change in the kernel's behaviour. So on the
older trees the underlying logic - and hence this documented example -
is genuinely different, and this patch wouldn't apply cleanly there
anyway. Pointing Fixes at 2a0e49279850 therefore wouldn't help
backports.

So using

Fixes: e54ac586674d ("cpufreq: editing corrections to cpufreq.rst")

seems reasonable.

Either way, the fix is fine to me:

Reviewed-by: Zhongqiu Han <zhongqiu.han@oss.qualcomm.com>




> 
>>   
>>   ``up_threshold``
>>   	If the estimated CPU load is above this value (in percent), the governor
> 


-- 
Thx and BRs,
Zhongqiu Han

Re: [PATCH] Documentation: admin-guide: pm: cpufreq: fix sampling_rate example command

[Rafael J. Wysocki (Intel)]

On Sun, Jun 21, 2026 at 7:57 AM Zhongqiu Han
<zhongqiu.han@oss.qualcomm.com> wrote:
>
> On 6/21/2026 11:52 AM, Randy Dunlap wrote:
> >
> >
> > On 6/20/26 7:25 PM, wangxiaodong wrote:
> >> The example shell command for setting ondemand's sampling_rate wraps an
> >> arithmetic expansion $((...)) in command-substitution backticks. The
> >> arithmetic result is then executed as a command, which fails and writes
> >> an empty value. Drop the surrounding backticks so the computed value is
> >> passed to echo as intended.
> >>
> >> Signed-off-by: wangxiaodong <wangxiaodong827546786@gmail.com>
> >> ---
> >>   Documentation/admin-guide/pm/cpufreq.rst | 2 +-
> >>   1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/Documentation/admin-guide/pm/cpufreq.rst b/Documentation/admin-guide/pm/cpufreq.rst
> >> index 8831cface585..34baf20cc202 100644
> >> --- a/Documentation/admin-guide/pm/cpufreq.rst
> >> +++ b/Documentation/admin-guide/pm/cpufreq.rst
> >> @@ -497,7 +497,7 @@ This governor exposes the following tunables:
> >>      represented by it to be 1.5 times as high as the transition latency
> >>      (the default)::
> >>
> >> -    # echo `$(($(cat cpuinfo_transition_latency) * 3 / 2))` > ondemand/sampling_rate
> >> +    # echo $(($(cat cpuinfo_transition_latency) * 3 / 2)) > ondemand/sampling_rate
> >
> > Ugh. Thanks.
> > Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
> >
> > and possibly:
> > Fixes: e54ac586674d ("cpufreq: editing corrections to cpufreq.rst")
>
>
> Thanks Randy,
>
> Just to back up Randy's Fixes suggestion, the line evolved as follows
> (most recent first):
>
> 2025/04/04 e54ac586674d:  #echo `$((.. * 3 / 2))` >  (trailing ` added)
> 2024/10/17 29dcbea92460:  #echo `$((.. * 3 / 2))  >  (still dangling `)
> 2017/03/13 2a0e49279850:  #echo `$((.. * 750 / 1000)) > (dangling leading `)
>
> The stray backtick can be traced back to 2a0e49279850, but it was just a
> dangling backtick then. The closed command-substitution form fixed here
> was only reached after e54ac586674d added the trailing backtick. Note
> that the "750/1000 -> 3/2" change in 29dcbea92460 was not just a doc
> edit: it reflects an actual change in the kernel's behaviour. So on the
> older trees the underlying logic - and hence this documented example -
> is genuinely different, and this patch wouldn't apply cleanly there
> anyway. Pointing Fixes at 2a0e49279850 therefore wouldn't help
> backports.
>
> So using
>
> Fixes: e54ac586674d ("cpufreq: editing corrections to cpufreq.rst")
>
> seems reasonable.
>
> Either way, the fix is fine to me:
>
> Reviewed-by: Zhongqiu Han <zhongqiu.han@oss.qualcomm.com>

Applied as 7.3 material, thanks!