Re: [PATCH 00/30] PREEMPT_AUTO: support lazy rescheduling

[Raghavendra K T]

On 2/23/2024 11:58 AM, Raghavendra K T wrote:
> On 2/23/2024 8:44 AM, Ankur Arora wrote:
> > Thomas Gleixner <tglx@xxxxxxxxxxxxx> writes:
> >
> > > On Wed, Feb 21 2024 at 22:57, Raghavendra K T wrote:
> > > > On 2/21/2024 10:45 PM, Thomas Gleixner wrote:
> > > > > On Wed, Feb 21 2024 at 17:53, Raghavendra K T wrote:
> > > > > > Configuration tested.
> > > > > > a) Base kernel (6.7),
> > > > >
> > > > > Which scheduling model is the baseline using?
> > > >
> > > > baseline is also PREEMPT_DYNAMIC with voluntary preemption
> > > >
> > > > > > b) patched with PREEMPT_AUTO voluntary preemption.
> > > > > > c) patched with PREEMPT_DYNAMIC voluntary preemption.
> > >
> > > Which RCU variant do you have enabled with a, b, c ?
> > >
> > > I.e. PREEMPT_RCU=?
> >
> > Raghu please confirm this, but if the defaults were chosen
> > then we should have:
> >
> > > > baseline is also PREEMPT_DYNAMIC with voluntary preemption
> > PREEMPT_RCU=y
> >
> > > > > > b) patched with PREEMPT_AUTO voluntary preemption.
> >
> > If this was built with PREEMPT_VOLUNTARY then, PREEMPT_RCU=n.
> > If with CONFIG_PREEMPT, PREEMPT_RCU=y.
> >
> > Might be worth rerunning the tests with the other combination
> > as well (still with voluntary preemption).
> >
> > > > > > c) patched with PREEMPT_DYNAMIC voluntary preemption.
> > PREEMPT_RCU=y
>
> Hello Thomas, Ankur,
> Yes, Ankur's understanding is right, defaults were chosen all the time so
> for
> a) base 6.7.0+ + PREEMPT_DYNAMIC with voluntary preemption PREEMPT_RCU=y
> b) patched + PREEMPT_AUTO voluntary preemption. PREEMPT_RCU = n
> c) patched + PREEMPT_DYNAMIC with voluntary preemption PREEMPT_RCU=y

> I will check with other combination (CONFIG_PREEMPT/PREEMPT_RCU) for (b)
> and comeback if I see anything interesting.

I see that

d) patched + PREEMPT_AUTO=y voluntary preemption CONFIG_PREEMPT, 
PREEMPT_RCU = y

All the results at 80% confidence
		case (d)
HashJoin         0%
Graph500         0%
XSBench          +1.2%
NAS-ft           +2.1%

In general averages are better for all the benchmarks but at 99%
confidence there seem to be no difference.

Overall looks on par or better for case (d)

Thanks and Regards
- Raghu