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SubjectRe: [PATCH] cpu-topology: warn if NUMA configurations conflicts with lower layer
On Mon, Dec 23, 2019 at 04:16:19PM +0800, z00214469 wrote:
> As we know, from sched domain's perspective, the DIE layer should be
> larger than or at least equal to the MC layer, and in some cases, MC
> is defined by the arch specified hardware, MPIDR for example, but NUMA
> can be defined by users,

Who are the users you are referring above ?

> with the following system configrations:

Do you mean ACPI tables or DT or some firmware tables ?

> *************************************
> NUMA: 0-2, 3-7

Is the above simply wrong with respect to hardware and it actually match
core_siblings ?

> core_siblings: 0-3, 4-7
> *************************************
> Per the current code, for core 3, its MC cpu map fallbacks to 3~7(its
> core_sibings is 0~3 while its numa node map is 3~7).
>
> For the sched MC, when we are build sched groups:
> step1. core3 's sched groups chain is built like this: 3->4->5->6->7->3
> step2. core4's sched groups chain is built like this: 4->5->6->7->4
> so after step2, core3's sched groups for MC level is overlapped, more
> importantly, it will fall to dead loop if while(sg != sg->groups)
>
> Obviously, the NUMA node with cpu 3-7 conflict with the MC level cpu
> map, but unfortunately, there is no way even detect such cases.
>

Again, is cpu 3-7 actually in a NUMA node or is it 4-7 ?

> In this patch, prompt a warning message to help with the above cases.
>
> Signed-off-by: Zeng Tao <prime.zeng@hisilicon.com>
> ---
> drivers/base/arch_topology.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
> index 1eb81f11..5fe44b3 100644
> --- a/drivers/base/arch_topology.c
> +++ b/drivers/base/arch_topology.c
> @@ -439,10 +439,18 @@ const struct cpumask *cpu_coregroup_mask(int cpu)
> if (cpumask_subset(&cpu_topology[cpu].core_sibling, core_mask)) {
> /* not numa in package, lets use the package siblings */
> core_mask = &cpu_topology[cpu].core_sibling;
> - }
> + } else
> + pr_warn_once("Warning: suspicous broken topology: cpu:[%d]'s core_sibling:[%*pbl] not a subset of numa node:[%*pbl]\n",
> + cpu, cpumask_pr_args(&cpu_topology[cpu].core_sibling),
> + cpumask_pr_args(core_mask));
> +

Won't this print warning on all systems that don't have numa within a
package ? What are you trying to achieve here ?

> if (cpu_topology[cpu].llc_id != -1) {
> if (cpumask_subset(&cpu_topology[cpu].llc_sibling, core_mask))
> core_mask = &cpu_topology[cpu].llc_sibling;
> + else
> + pr_warn_once("Warning: suspicous broken topology: cpu:[%d]'s llc_sibling:[%*pbl] not a subset of numa node:[%*pbl]\n",
> + cpu, cpumask_pr_args(&cpu_topology[cpu].llc_sibling),
> + cpumask_pr_args(core_mask));
> }
>

This will trigger warning on all systems that lack cacheinfo topology.
I don't understand the intent of this patch at all. Can you explain
all the steps you follow and the issue you face ?

--
Regards,
Sudeep

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