linux-kernel - Re: [PATCH v5 1/4] smpboot: introduce SDTL_INIT() helper to tidy sched topology setup

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250711130601.GD905792@noisy.programming.kicks-ass.net>
Date: Fri, 11 Jul 2025 15:06:01 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: K Prateek Nayak <kprateek.nayak@....com>
Cc: Li Chen <me@...ux.beauty>, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
	"H . Peter Anvin" <hpa@...or.com>,
	"Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
	Sohil Mehta <sohil.mehta@...el.com>,
	Brian Gerst <brgerst@...il.com>,
	Patryk Wlazlyn <patryk.wlazlyn@...ux.intel.com>,
	linux-kernel@...r.kernel.org,
	Madhavan Srinivasan <maddy@...ux.ibm.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Nicholas Piggin <npiggin@...il.com>,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	Heiko Carstens <hca@...ux.ibm.com>,
	Vasily Gorbik <gor@...ux.ibm.com>,
	Alexander Gordeev <agordeev@...ux.ibm.com>,
	Christian Borntraeger <borntraeger@...ux.ibm.com>,
	Sven Schnelle <svens@...ux.ibm.com>,
	Juri Lelli <juri.lelli@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
	Valentin Schneider <vschneid@...hat.com>,
	Thomas Weißschuh <thomas.weissschuh@...utronix.de>,
	Li Chen <chenl311@...natelecom.cn>,
	Huacai Chen <chenhuacai@...nel.org>, Bibo Mao <maobibo@...ngson.cn>,
	Tobias Huschle <huschle@...ux.ibm.com>,
	Mete Durlu <meted@...ux.ibm.com>,
	Joel Granados <joel.granados@...nel.org>,
	Guo Weikang <guoweikang.kernel@...il.com>,
	Swapnil Sapkal <swapnil.sapkal@....com>,
	linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org
Subject: Re: [PATCH v5 1/4] smpboot: introduce SDTL_INIT() helper to tidy
 sched topology setup

On Fri, Jul 11, 2025 at 11:20:30AM +0530, K Prateek Nayak wrote:
> On 7/10/2025 4:27 PM, Li Chen wrote:
> >  	/*
> >  	 * .. and append 'j' levels of NUMA goodness.
> >  	 */
> >  	for (j = 1; j < nr_levels; i++, j++) {
> > -		tl[i] = (struct sched_domain_topology_level){
> > -			.mask = sd_numa_mask,
> > -			.sd_flags = cpu_numa_flags,
> > -			.flags = SDTL_OVERLAP,
> > -			.numa_level = j,
> > -			SD_INIT_NAME(NUMA)
> > -		};
> > +		tl[i] = SDTL_INIT(sd_numa_mask, cpu_numa_flags, NUMA);
> > +		tl[i].numa_level = j;
> > +		tl[i].flags = SDTL_OVERLAP;
> 
> Tangential discussion: I was looking at this and was wondering why we
> need a "tl->flags" when there is already sd_flags() function and we can
> simply add SD_OVERLAP to sd_numa_flags().
> 
> I think "tl->flags" was needed when the idea of overlap domains was
> added in commit e3589f6c81e4 ("sched: Allow for overlapping sched_domain
> spans") when it depended on "FORCE_SD_OVERLAP" sched_feat() which
> allowed toggling this off but that was done away with in commit
> af85596c74de ("sched/topology: Remove FORCE_SD_OVERLAP") so perhaps we
> can get rid of it now?
> 
> Relying on SD_NUMA should be enough currently. Peter, Valentin, what do
> you think of something like below?

I think you're right. SD_NUMA appears to be the one and only case that
also has SDTL_OVERLAP which then results in setting SD_OVERLAP, making
SD_NUMA and SD_OVERLAP equivalent and SDTL_OVERLAP redundant.

I'll presume you're okay with me adding your SoB to things, and I'll
push out all 5 patches to queue/sched/core to let the robots have a go
at things.