Re: [PATCH] sched: Add a new version sysctl to control child runs first

[CGEL]

On Mon, Sep 13, 2021 at 10:13:54AM +0200, Peter Zijlstra wrote:
> On Sun, Sep 12, 2021 at 04:12:23AM +0000, cgel.zte@xxxxxxxxx wrote:
> > From: Yang Yang <yang.yang29@xxxxxxxxxx>
> > 
> > The old version sysctl has some problems. First, it allows set value
> > bigger than 1, which is unnecessary. Second, it didn't follow the
> > rule of capabilities. Thirdly, it didn't use static key. This new
> > version fixes all the problems.
> 
> Does any of that actually matter?

For the first problem, I think the reason why sysctl_schedstats() only
accepts 0 or 1, is suitbale for sysctl_child_runs_first(). Since
task_fork_fair() only need sysctl_sched_child_runs_first to be
zero or non-zero.

For the second problem, I remember there is a rule: try to
administration system through capilities but not depends on
root identity. Just like sysctl_schedstats() or other
sysctl_xx().

For the thirdly problem, sysctl_child_runs_first maynot changes
often, but may accessed often, like static_key delayacct_key
controlled by sysctl_delayacct().

Thanks!