Re: smpboot seems to be confused on dual EPYC system

Borislav Petkov
2018-05-27T20:07:13Z

On Sun, May 20, 2018 at 03:23:32PM +0200, Gabriel C wrote:
> Hello,
>
> I have an H11DSi-NT board with 2 * EPYC 7281 16C/32T CPUs.
>
> On that box for some reason spmboot things '4' logical packages
> are possible.

First of all, which kernel?

> Max CPUs can be 128 ( 2 * 32C/64T ), however only 2 CPUs are possible
> not 4 and therefor there is no way to add other 64 hotplug CPUs.
> ( not even sure cpu hotplug will work here )
>
> $ dmesg | egrep "smpboot|NR_CPUS|CPUs"
> [ 0.000000] smpboot: Allowing 128 CPUs, 64 hotplug CPUs

Your BIOS is made to support 32-Core CPUs too.

> [ 0.000000] setup_percpu: NR_CPUS:8192 nr_cpumask_bits:128
> nr_cpu_ids:128 nr_node_ids:8
> [ 0.000000] SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=128, Nodes=8
> [ 0.000000] RCU restricting CPUs from NR_CPUS=8192 to nr_cpu_ids=128.
> [ 0.037000] smpboot: CPU0: AMD EPYC 7281 16-Core Processor (family:
> 0x17, model: 0x1, stepping: 0x2)

That says 2 * 16C * 2T = 64T.

> [ 0.048005] smp: Bringing up secondary CPUs ...
> [ 0.055042] .... node #0, CPUs: #1 #2 #3
> [ 0.079029] .... node #1, CPUs: #4 #5 #6 #7
> [ 0.111049] .... node #2, CPUs: #8 #9 #10 #11
> [ 0.143050] .... node #3, CPUs: #12 #13 #14 #15
> [ 0.175031] .... node #4, CPUs: #16 #17 #18 #19
> [ 0.217031] .... node #5, CPUs: #20 #21 #22 #23
> [ 0.249062] .... node #6, CPUs: #24 #25 #26 #27
> [ 0.281058] .... node #7, CPUs: #28 #29 #30 #31
> [ 0.313028] .... node #0, CPUs: #32 #33 #34 #35
> [ 0.345028] .... node #1, CPUs: #36 #37 #38 #39
> [ 0.377046] .... node #2, CPUs: #40 #41 #42 #43
> [ 0.409043] .... node #3, CPUs: #44 #45 #46 #47
> [ 0.441028] .... node #4, CPUs: #48 #49 #50 #51
> [ 0.473029] .... node #5, CPUs: #52 #53 #54 #55
> [ 0.505060] .... node #6, CPUs: #56 #57 #58 #59
> [ 0.537052] .... node #7, CPUs: #60 #61 #62 #63
> [ 0.562171] smp: Brought up 8 nodes, 64 CPUs
> [ 0.562171] smpboot: Max logical packages: 4
> [ 0.562171] smpboot: Total of 64 processors activated (268089.53 BogoMIPS)

You have 64 logical CPUs.

So what is the problem?

--
Regards/Gruss,
Boris.

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