From: Michael Ellerman <mpe@ellerman•id.au>
To: Oliver O'Halloran <oohall@gmail•com>, linuxppc-dev@lists•ozlabs.org
Cc: Oliver O'Halloran <oohall@gmail•com>
Subject: Re: [PATCH 1/5] powerpc/smp: use cpu_to_chip_id() to find siblings
Date: Wed, 15 Mar 2017 22:18:22 +1100 [thread overview]
Message-ID: <877f3qlrep.fsf@concordia.ellerman.id.au> (raw)
In-Reply-To: <20170302004920.21948-1-oohall@gmail.com>
Oliver O'Halloran <oohall@gmail•com> writes:
> To determine which logical CPUs are on the same core the kernel uses the
> ibm,chipid property from the device tree node associated with that cpu.
> The lookup for this this information is currently open coded in both
> traverse_siblings() and traverse_siblings_chip_id(). This patch replaces
> these manual lookups with the existing cpu_to_chip_id() function.
Some minor nits.
cpu_to_chip_id() actually searches recursively up the parents until it
finds a ibm,chip-id, so it's not a 1:1 replacement for the existing
logic, but it's probably still an OK conversion. It's still worth
mentioning in the change log thought.
> diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
> index 893bd7f79be6..dfe0e1d9cd06 100644
> --- a/arch/powerpc/kernel/smp.c
> +++ b/arch/powerpc/kernel/smp.c
> @@ -664,23 +655,19 @@ static void traverse_core_siblings(int cpu, bool add)
> {
> struct device_node *l2_cache, *np;
> const struct cpumask *mask;
> - int i, chip, plen;
> - const __be32 *prop;
> + int chip_id;
> + int i;
>
> - /* First see if we have ibm,chip-id properties in cpu nodes */
> - np = of_get_cpu_node(cpu, NULL);
> - if (np) {
> - chip = -1;
> - prop = of_get_property(np, "ibm,chip-id", &plen);
> - if (prop && plen == sizeof(int))
> - chip = of_read_number(prop, 1);
> - of_node_put(np);
> - if (chip >= 0) {
> - traverse_siblings_chip_id(cpu, add, chip);
> - return;
> - }
> + /* threads that share a chip-id are considered siblings (same die) */
You might know it means the "same die", but AFAIK there's no actual
definition for what the chip-id means, so let's not write comments that
might be wrong in future. Just saying they're considered siblings is
sufficient.
Also "Threads" :)
cheers
next prev parent reply other threads:[~2017-03-15 11:18 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-02 0:49 [PATCH 1/5] powerpc/smp: use cpu_to_chip_id() to find siblings Oliver O'Halloran
2017-03-02 0:49 ` [PATCH 2/5] powerpc/smp: add set_cpus_related() Oliver O'Halloran
2017-03-15 11:18 ` Michael Ellerman
2017-03-23 1:27 ` Oliver O'Halloran
2017-03-28 1:15 ` Michael Ellerman
2017-03-02 0:49 ` [PATCH 3/5] powerpc/smp: Add update_cpu_masks() Oliver O'Halloran
2017-03-15 11:18 ` Michael Ellerman
2017-03-02 0:49 ` [PATCH 4/5] powerpc/smp: add cpu_cache_mask Oliver O'Halloran
2017-03-15 11:26 ` Michael Ellerman
2017-03-23 3:33 ` Oliver O'Halloran
2017-03-28 1:05 ` Michael Ellerman
2017-03-02 0:49 ` [PATCH 5/5] powerpc/smp: Add Power9 scheduler topology Oliver O'Halloran
2017-03-02 10:25 ` Balbir Singh
2017-03-15 11:33 ` Michael Ellerman
2017-03-15 11:30 ` Michael Ellerman
2017-03-02 3:44 ` [PATCH 1/5] powerpc/smp: use cpu_to_chip_id() to find siblings Balbir Singh
2017-03-15 11:18 ` Michael Ellerman [this message]
2017-03-23 1:09 ` Oliver O'Halloran
2017-03-28 3:03 ` Michael Ellerman
2017-03-28 3:23 ` Oliver O'Halloran
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