Andrew,
On Wed, Mar 5, 2014 at 5:07 AM, Andrew Clayton
<andrew@xxxxxxxxxxxxxxxxxx> wrote:
> The {get,set}priority man pages currently lists the process's priority
> range as being from 40..1 however it should be 40..0 as 0 would be for
> a nice of -20.
I don't think this is correct. Without actually re-checking the kernel
source, this is what I think is correct:
k-nice (the internal kernel value) has the range 40..1.
u-nice (the user-space value) has the range -20..+19
and u-nice = 20 - k-nice
(In fact, looking further down the man page, I see this is all
explained. Note that there is no +20 nice value on Linux.)
Cheers,
Michael
> Signed-off-by: Andrew Clayton <andrew@xxxxxxxxxxxxxxxxxx>
> ---
>
> Perhaps the 40 should be 39 as the kernel seems to limit the nice range
> from -20 to 19 in kernel/sched/core.c::set_user_nice().
>
> man2/getpriority.2 | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/man2/getpriority.2 b/man2/getpriority.2
> index b39bdcf..066cf75 100644
> --- a/man2/getpriority.2
> +++ b/man2/getpriority.2
> @@ -197,7 +197,7 @@ The actual priority range varies between kernel versions.
> Linux before 1.3.36 had \-infinity..15.
> Since kernel 1.3.43, Linux has the range \-20..19.
> Within the kernel, nice values are actually represented
> -using the corresponding range 40..1
> +using the corresponding range 40..0
> (since negative numbers are error codes) and these are the values
> employed by the
> .BR setpriority ()
> --
> 1.8.5.3
>
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
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