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Itanium CPU count: who's reporting the right number?

 
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David G. Douthitt
Regular Advisor

Itanium CPU count: who's reporting the right number?

HP-UX Glance reports on an rx2660 with Itanium 2 processors (Montecito?) that there are four processors numbered 0, 2, 4, and 6.

MP reports (using SS command) that there are two processor modules.

EFI reports two processors, each with four logical processors - for a total of eight - with hyperthreading enabled.

HP-UX machinfo reports 2 Intanium 2 9000 series processors, with 4 logical processors, 2 per socket.

STM shows four CPUs in its map. In the system information log, it lists the processors as product MONT_C2_16 18 (part no. AB577-2100B).

Question is: who's right and why are the others wrong? The only thing I'm fairly certain of is that EFI is, in some fashion, authoritative - but it lists eight cores with hyperthreading, and nothing else sees eight cores.

I did some looking up of EFI and its PAL (Processor Abstraction Layer) and SAL (System Abstraction Layer); I suspect these two may have something to do with it.

All other HP-UX Itanium systems here (rx4640, rx6600) have easily corresponding CPUs with a sequential and accurate count from Glance.
6 REPLIES 6
Torsten.
Acclaimed Contributor

Re: Itanium CPU count: who's reporting the right number?

The Itanium 2 9000 series processors (Montecito) is a dual core, so you have 2 cores per module.

With hyperthreading = on only EFI reports 4 "logical" CPUS per module, but in fact you only have 2 physical per module.

PROCESSOR MODULE INFORMATION

# of L3 L4 Family/
CPU Logical Cache Cache Model Processor
Module CPUs Speed Size Size (hex.) Rev State
------ ------- -------- ------ ------ ------- --- ------------
0 4 1.6 GHz 9 MB None 20/00 C2 Active
1 4 1.6 GHz 9 MB None 20/00 C2 Active
2 4 1.6 GHz 9 MB None 20/00 C2 Active
3 4 1.6 GHz 9 MB None 20/00 C2 Active

CPU threads are turned on.


.....

PROCESSOR MODULE INFORMATION

# of L3 L4 Family/
CPU Logical Cache Cache Model Processor
Module CPUs Speed Size Size (hex.) Rev State
------ ------- -------- ------ ------ ------- --- ------------
0 2 1.4 GHz 6 MB None 20/00 C2 Active

CPU threads are turned off.

Hope this helps!
Regards
Torsten.

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rick jones
Honored Contributor

Re: Itanium CPU count: who's reporting the right number?

Likely as not they are all correct - it is a question of context. Also depends on what one calls a processor vs a CPU vs a core vs a thread etc etc

Montecito is a single chip/processor with two cores, each of which has two threads.


EFI will report what is enabled at the HW/FW level. It calls a core a logical processor.

IIRC MP reports FRU's or things close to FRU, so it will just show the two processor modules (chips).

Glance will report what the OS tells it is there. Similar for machinfo. By default, while threading is enabled in the FW, the UX OS will "park" one thread on each core (logical processor) and not use it unless explicitly enabled through the OS.
there is no rest for the wicked yet the virtuous have no pillows
David G. Douthitt
Regular Advisor

Re: Itanium CPU count: who's reporting the right number?

These replies are fantastic. However, you did miss a few things that I found out while researching this "problem".

HP uses the concept of logical CPUs (or LCPUs). On the Montecito processors, each CPU thread is one LCPU - thus EFI is reporting correctly: there are 2 CPUs, each with 2 cores and each core with 2 threads: 2 cores * 2 threads = 4 LCPUs per physical CPU (not core).

The kernel tunable lcpu_attr will activate use of hyperthreading by the OS; this will cause Glance to report on eight cores instead of four (as the "missing cores" will now show up as being in use).

The command is immediate and is:

kctune lcpu_attr=1

...to enable.

Curious as to why this wasn't a source of confusion in the other machines (rx4640 for instance, or rx6600) but I gather it's just because they're different CPUs...
rick jones
Honored Contributor
Solution

Re: Itanium CPU count: who's reporting the right number?

An rx4640 could be either Montectio or Madison (single core no threading) processors. An rx6600 is going to have Montecito processors.

Some of the tunable stuff in UX may be specific to 11.31 or later versions of 11.23.

IIRC one can enable/disable use of HW threading on a processor set by processor set basis in HP-UX.
there is no rest for the wicked yet the virtuous have no pillows
Nyck_1
Super Advisor

Re: Itanium CPU count: who's reporting the right number?

Here is another way:-

From EFI boot manager select "System Configuration"

=>System configuration select "Advanced System Information"

=> from Advanced system information select "Display All information"

PROCESSOR MODULE INFORMATION


# of L3 L4 Family/

CPU Logical Cache Cache Model Processor

Module CPUs Speed Size Size (hex.) Rev State

------ ------- -------- ------ ------ ------- --- ------------

0 2 1.6 GHz 9 MB None 20/00 C2 Active

1 2 1.6 GHz 9 MB None 20/00 C2 Active
Steven E. Protter
Exalted Contributor

Re: Itanium CPU count: who's reporting the right number?

Shalom,

This gets to be more and more fun as Intel keeps stuffing more cores into the CPU.

Right now the dual core is being used in Itanium servers and each core shows up on some software measures as a CPU. Some software is sophisticated enough to discern a Core and show it as a single CPU.

This dips you into the licensing debate.

HP licenses serviceguard and many other tools by the CPU. That means a 4 CPU system requires 4 licenses to get full support.

But Oracle has said in public that each core is a CPU and is subject to their $20,000 or $40,000 per CPU license policy.

Fun Fun Fun.

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Steven E Protter
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