Re: [PATCH] x86/smpboot: Make logical package management more robust

Peter Zijlstra
2016-12-08T12:08:44Z

On Thu, Dec 08, 2016 at 10:04:25AM +0100, Thomas Gleixner wrote:
> @@ -289,16 +293,17 @@ int topology_update_package_map(unsigned
> if (test_and_set_bit(pkg, physical_package_map))
> goto found;
>
> - if (logical_packages_frozen) {
> - physical_to_logical_pkg[pkg] = -1;
> - pr_warn("APIC(%x) Package %u exceeds logical package max\n",
> - apicid, pkg);
> + if (logical_packages >= __max_logical_packages) {
> + pr_warn("Package %u of CPU %u exceeds BIOS package data %u.\n",
> + logical_packages, cpu, __max_logical_packages);
> return -ENOSPC;
> }
>
> new = logical_packages++;
> - pr_info("APIC(%x) Converting physical %u to logical package %u\n",
> - apicid, pkg, new);
> + if (new != pkg) {
> + pr_info("CPU %u Converting physical %u to logical package %u\n",
> + cpu, pkg, new);
> + }

This makes the print conditional on the phy<->logical mapping not
matching; I thought it was a concious decision to print everything in
the initial version.

This way, if we have a 4 node system and nodes 1,2 are crossed we'll
only see:

"Converting physical 2 to logical package 1"
"Converting physical 1 to logical package 2"

And nothing on the other two nodes, which could be slightly confusing.

> physical_to_logical_pkg[pkg] = new;
>
> found:

> @@ -366,27 +371,9 @@ static void __init smp_init_package_map(
> size = BITS_TO_LONGS(max_physical_pkg_id) * sizeof(unsigned long);
> physical_package_map = kzalloc(size, GFP_KERNEL);
>
> - for_each_present_cpu(cpu) {
> - unsigned int apicid = apic->cpu_present_to_apicid(cpu);
> -
> - if (apicid == BAD_APICID || !apic->apic_id_valid(apicid))
> - continue;
> - if (!topology_update_package_map(apicid, cpu))
> - continue;
> - pr_warn("CPU %u APICId %x disabled\n", cpu, apicid);
> - per_cpu(x86_bios_cpu_apicid, cpu) = BAD_APICID;
> - set_cpu_possible(cpu, false);
> - set_cpu_present(cpu, false);
> - }
> -
> - if (logical_packages > __max_logical_packages) {
> - pr_warn("Detected more packages (%u), then computed by BIOS data (%u).\n",
> - logical_packages, __max_logical_packages);
> - logical_packages_frozen = true;
> - __max_logical_packages = logical_packages;

So we'll never 'shrink' the initially computed max; which could result
in using more memory than strictly needed, otoh it makes physical
hotplug happier.

> - }
> -
> pr_info("Max logical packages: %u\n", __max_logical_packages);
> +
> + topology_update_package_map(pkg, cpu);
> }