linux-kernel - Re: [Patch v2 2/6] sched/topology: Record number of cores in sched group

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 for Android: free password hash cracker in your pocket

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

Message-ID: <f493a770e15a81aaad2e13d8afe1daf939b8267a.camel@linux.intel.com>
Date:   Mon, 12 Jun 2023 13:16:52 -0700
From:   Tim Chen <tim.c.chen@...ux.intel.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Ricardo Neri <ricardo.neri@...el.com>,
        "Ravi V . Shankar" <ravi.v.shankar@...el.com>,
        Ben Segall <bsegall@...gle.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Len Brown <len.brown@...el.com>, Mel Gorman <mgorman@...e.de>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Valentin Schneider <vschneid@...hat.com>,
        Ionela Voinescu <ionela.voinescu@....com>, x86@...nel.org,
        linux-kernel@...r.kernel.org,
        Shrikanth Hegde <sshegde@...ux.vnet.ibm.com>,
        Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
        naveen.n.rao@...ux.vnet.ibm.com,
        Yicong Yang <yangyicong@...ilicon.com>,
        Barry Song <v-songbaohua@...o.com>,
        Chen Yu <yu.c.chen@...el.com>, Hillf Danton <hdanton@...a.com>
Subject: Re: [Patch v2 2/6] sched/topology: Record number of cores in sched
 group

On Mon, 2023-06-12 at 13:29 +0200, Peter Zijlstra wrote:
> On Thu, Jun 08, 2023 at 03:32:28PM -0700, Tim Chen wrote:
> > 
> >  		sg->group_weight = cpumask_weight(sched_group_span(sg));
> >  
> > +		cpumask_copy(mask, sched_group_span(sg));
> > +		for_each_cpu(cpu, mask) {
> > +			cores++;
> > +			cpumask_andnot(mask, mask, cpu_smt_mask(cpu));
> > +		}
> > +		sg->cores = cores;
> > +
> >  		if (!(sd->flags & SD_ASYM_PACKING))
> >  			goto next;
> 
> Just a note; not sure we want or can do anything about this, but
> consider someone doing partitions like:
> 
> 	[0,1] [2,3] [3,6]
> 	[------] [------]
> 
> That is, 3 SMT cores, and 2 partitions splitting an SMT core in two.
> 
> Then the domain trees will see either 2 or 3 but not the fully core.
> 
> I'm perfectly fine with saying: don't do that then.

I also can't see a reason to split SMT between two domains.

Tim