Re: [RFC PATCH 10/10] timer: Lower base clock forwarding threshold

Frederic Weisbecker
2020-07-03T00:12:25Z

On Thu, Jul 02, 2020 at 05:14:23PM +0200, Thomas Gleixner wrote:
> Frederic Weisbecker <frederic@kernel.org> writes:
> > On Thu, Jul 02, 2020 at 03:21:35PM +0200, Thomas Gleixner wrote:
> > The following part:
> >
> >> > * Also while executing timers, base->clk is 1 offset ahead
> >> > * of jiffies to avoid endless requeuing to current jffies.
> >> > */
> >
> > relates to situation when (long)(jnow - base->clk) < 0
>
> This still is inconsistent with your changelog:

Right.

>
> > There is no apparent reason for not forwarding base->clk when it's 2
> > jiffies late
>
> Let's do the math:
>
> jiffies = 4
> base->clk = 2
>
> 4 - 2 = 2
>
> which means it is forwarded when it's 2 jiffies late with the original
> code, because 2 < 2.
>
> The reason for this < 2 is historical and goes back to the oddities of
> the original timer wheel before the big rewrite.

Ok. And is it still needed today or can we now forward even with a 1 delta?