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

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Date: Wed, 21 Feb 2024 17:53:36 +0530
From: Raghavendra K T <raghavendra.kt@....com>
To: Ankur Arora <ankur.a.arora@...cle.com>, linux-kernel@...r.kernel.org
Cc: tglx@...utronix.de, peterz@...radead.org, torvalds@...ux-foundation.org,
 paulmck@...nel.org, akpm@...ux-foundation.org, luto@...nel.org,
 bp@...en8.de, dave.hansen@...ux.intel.com, hpa@...or.com, mingo@...hat.com,
 juri.lelli@...hat.com, vincent.guittot@...aro.org, willy@...radead.org,
 mgorman@...e.de, jpoimboe@...nel.org, mark.rutland@....com, jgross@...e.com,
 andrew.cooper3@...rix.com, bristot@...nel.org,
 mathieu.desnoyers@...icios.com, geert@...ux-m68k.org,
 glaubitz@...sik.fu-berlin.de, anton.ivanov@...bridgegreys.com,
 mattst88@...il.com, krypton@...ich-teichert.org, rostedt@...dmis.org,
 David.Laight@...LAB.COM, richard@....at, mjguzik@...il.com,
 jon.grimm@....com, bharata@....com, boris.ostrovsky@...cle.com,
 konrad.wilk@...cle.com
Subject: Re: [PATCH 00/30] PREEMPT_AUTO: support lazy rescheduling

On 2/13/2024 11:25 AM, Ankur Arora wrote:
> Hi,
> 
> This series adds a new scheduling model PREEMPT_AUTO, which like
> PREEMPT_DYNAMIC allows dynamic switching between a none/voluntary/full
> preemption model. However, unlike PREEMPT_DYNAMIC, it doesn't depend
> on explicit preemption points for the voluntary models.
> 
> The series is based on Thomas' original proposal which he outlined
> in [1], [2] and in his PoC [3].
> 
> An earlier RFC version is at [4].
> 

[...]

Hello Ankur,
Thank you for the series. Just giving a crisp summary since I am
expecting a respin of patchseries with minor changes suggested by
Thomas, Mark and a fix by Paul. and looking forward to test that.

I was able to test the current patchset rather in a different way.

On Milan, (2 node, 256 cpu,  512GB RAM), Did my regular benchmark
testing, to see if there are any surprises.

Will do more detailed testing/analysis w/ some of the scheduler specific
tests also after your respin.

Configuration tested.
a) Base kernel (6.7),
b) patched with PREEMPT_AUTO voluntary preemption.
c) patched with PREEMPT_DYNAMIC voluntary preemption.

Workloads I tested and their %gain,
                    case b                   case c
NAS                +2.7                    +1.9
Hashjoin,          +0			     +0
Graph500,  	   -6 			     +0
XSBench		   +1.7			     +0

Did kernbench etc test from Mel's mmtests suite also. Did not notice
much difference.

In summary benchmarks are mostly on positive side.

Thanks and Regards
- Raghu