linux-kernel - Re: [PATCH v6 2/2] powerpc: Use cpu_smallcore_sibling

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Message-Id: <20180813120732.GA13369@in.ibm.com>
Date:   Mon, 13 Aug 2018 17:37:32 +0530
From:   Gautham R Shenoy <ego@...ux.vnet.ibm.com>
To:     Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc:     "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Michael Neuling <mikey@...ling.org>,
        Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
        Akshay Adiga <akshay.adiga@...ux.vnet.ibm.com>,
        Shilpasri G Bhat <shilpa.bhat@...ux.vnet.ibm.com>,
        "Oliver O'Halloran" <oohall@...il.com>,
        Nicholas Piggin <npiggin@...il.com>,
        Murilo Opsfelder Araujo <muriloo@...ux.ibm.com>,
        Anton Blanchard <anton@...ba.org>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 2/2] powerpc: Use cpu_smallcore_sibling_mask at SMT
 level on bigcores

On Thu, Aug 09, 2018 at 06:26:57AM -0700, Srikar Dronamraju wrote:
> * Gautham R. Shenoy <ego@...ux.vnet.ibm.com> [2018-08-09 11:02:08]:
> 
> > 
> > 3) ppc64_cpu --smt=2
> >    SMT domain ceases to exist as each domain consists of just one
> >    group.
> > 
> 
> When seen in isolation, the above looks as if ppc64_cpu --smt=2 o/p says
> " SMT domain ceases to exist...."

Ok. The intent was to say that one of the sched-domain level
collapses, thereby leaving only CACHE, DIE and NUMA. Will word it
better.

> 
> > @@ -999,7 +1012,17 @@ static void add_cpu_to_masks(int cpu)
> >  {
> >  	int first_thread = cpu_first_thread_sibling(cpu);
> >  	int chipid = cpu_to_chip_id(cpu);
> > -	int i;
> > +
> > +	struct thread_groups tg;
> > +	int i, cpu_group_start = -1;
> > +
> > +	if (has_big_cores) {
> > +		struct device_node *dn = of_get_cpu_node(cpu, NULL);
> > +
> 
> Not checking for validity of dn and no of_node_puts?

Will fix this. Thanks for catching this.

> 
> > +		parse_thread_groups(dn, &tg);
> > +		cpu_group_start = get_cpu_thread_group_start(cpu, &tg);
> > +		cpumask_set_cpu(cpu, cpu_smallcore_sibling_mask(cpu));
> > +	}
> > 
> >  	/*
> >  	 * This CPU will not be in the online mask yet so we need to manually
> 
> The rest looks good

Thanks for the review.


>