Re: smpboot seems to be confused on dual EPYC system

Gabriel C
2018-05-27T21:37:43Z

( sorry I didn't noticed google changed here something , resending to
the list as plain text)

2018-05-27 23:22 GMT+02:00 Gabriel C <nix.or.die@gmail.com>:
>
> 2018-05-27 22:07 GMT+02:00 Borislav Petkov <bp@alien8.de>:
>>
>> 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?
>
>
> That box runs right now 4.16.11
>>
>>
>> > 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.
>
>
> 128 CPUs are maximal possible however there is no way to have
> 2 CPUs fully populated , in this case 64C and have another 64 hotplug CPUs
>
> That would mean that's an s4 system while impossible with EPYCs.
>>
>>
>> > [ 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.
>
>
> That says whole topology is set to 128 no ?
> Eg to max possible but not to what the system runs now.
>
>>
>>
>> > [ 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?
>>
>
> The problem is that being wrong ..
>
> >[ 0.562171] smpboot: Max logical packages: 4
>
> These are max 2 not 4.
>
> Regards
>