On 09/03/2022 19:26, Darren Hart wrote:
> On Wed, Mar 09, 2022 at 01:50:07PM +0100, Dietmar Eggemann wrote:
>> On 08/03/2022 18:49, Darren Hart wrote:
>>> On Tue, Mar 08, 2022 at 05:03:07PM +0100, Dietmar Eggemann wrote:
>>>> On 08/03/2022 12:04, Vincent Guittot wrote:
>>>>> On Tue, 8 Mar 2022 at 11:30, Will Deacon <will@xxxxxxxxxx> wrote:
>>
>> [...]
>>
>>>> IMHO, if core_mask weight is 1, MC will be removed/degenerated anyway.
>>>>
>>>> This is what I get on my Ampere Altra (I guess I don't have the ACPI
>>>> changes which would let to a CLS sched domain):
>>>>
>>>> # cat /sys/kernel/debug/sched/domains/cpu0/domain*/name
>>>> DIE
>>>> NUMA
>>>> root@oss-altra01:~# zcat /proc/config.gz | grep SCHED_CLUSTER
>>>> CONFIG_SCHED_CLUSTER=y
>>>
>>> I'd like to follow up on this. Would you share your dmidecode BIOS
>>> Information section?
>>
>> # dmidecode -t 0
>> # dmidecode 3.2
>> Getting SMBIOS data from sysfs.
>> SMBIOS 3.2.0 present.
>>
>> Handle 0x0000, DMI type 0, 26 bytes
>> BIOS Information
>> Vendor: Ampere(TM)
>> Version: 0.9.20200724
>> Release Date: 2020/07/24
>> ROM Size: 7680 kB
>> Characteristics:
>> PCI is supported
>> BIOS is upgradeable
>> Boot from CD is supported
>> Selectable boot is supported
>> ACPI is supported
>> UEFI is supported
>> BIOS Revision: 5.15
>> Firmware Revision: 0.6
>>
>
> Thank you, I'm following internally and will get with you.
Looks like in my PPTT, the `Processor Hierarchy Nodes` which represents
cluster nodes have no valid `ACPI Processor ID`.
Example for CPU0:
cpu_node-:
[1B9Ch 7068 1] Subtable Type : 00 [Processor Hierarchy Node]
[1B9Dh 7069 1] Length : 1C
[1B9Eh 7070 2] Reserved : 0000
[1BA0h 7072 4] Flags (decoded below) : 0000001A
Physical package : 0
ACPI Processor ID valid : 1 <-- valid !!!
Processor is a thread : 0
Node is a leaf : 1
Identical Implementation : 1
[1BA4h 7076 4] Parent : 00001B88 <-- parent !!!
[1BA8h 7080 4] ACPI Processor ID : 00001200 [1BACh 7084
4] Private Resource Number : 00000002
[1BB0h 7088 4] Private Resource : 00001B58
[1BB4h 7092 4] Private Resource : 00001B70
cluster_node (cpu_node->parent):
[1B88h 7048 1] Subtable Type : 00 [Processor Hierarchy Node]
[1B89h 7049 1] Length : 14
[1B8Ah 7050 2] Reserved : 0000
[1B8Ch 7052 4] Flags (decoded below) : 00000010
Physical package : 0
ACPI Processor ID valid : 0 <-- not valid !!!
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Processor is a thread : 0
Node is a leaf : 0
Identical Implementation : 1
[1B90h 7056 4] Parent : 000001C8
[1B94h 7060 4] ACPI Processor ID : 00000000
[1B98h 7064 4] Private Resource Number : 00000000
The code which checks this is:
int find_acpi_cpu_topology_cluster(unsigned int cpu)
{
....
if (cluster_node->flags & ACPI_PPTT_ACPI_PROCESSOR_ID_VALID)
retval = cluster_node->acpi_processor_id;
else
retval = ACPI_PTR_DIFF(cluster_node, table);
The else patch just returns distinct values for each CPU, so there is no
sub-grouping of CPUs which can lead to a CLS SD.
