Re: [PATCH v14 25/25] sched: use static key for sched_clock_running

Pavel Tatashin
2018-07-19T14:24:40Z

On Thu, Jul 19, 2018 at 6:49 AM Peter Zijlstra <peterz@infradead.org> wrote:
>
> On Tue, Jul 17, 2018 at 10:22:11PM -0400, Pavel Tatashin wrote:
> > sched_clock_running may be read every time sched_clock_cpu() is called.
> > Yet, this variable is updated only twice during boot, and never changes
> > again, therefore it is better to make it a static key.
>
> Right, so the focus was always on making the sane TSC case fast, and if
> TSC isn't stable we'd just make do and not care too much.
>

True for CONFIG_HAVE_UNSTABLE_SCHED_CLOCK, but for other systems like
SPARC, it hurts to have this variable accessed every time, even though
they have a sane sched_clock().

> But this certainly isn't wrong, so ACK.

Thank you,
Pave