Check out my first novel, midnight's simulacra!

SMP on x86

From dankwiki
Revision as of 13:49, 1 September 2009 by Dank (talk | contribs) (→‎See also)

The primary specification for multiprocessor x86-based setups is the Intel MultiProcessor Specification (last updated, AFAIK, to revision-006 on 1995-05-15).

Interrupts

[recombinator](0) $ cat /proc/interrupts 
           CPU0       CPU1       
  0:        491          0   IO-APIC-edge      timer
  8:         87          0   IO-APIC-edge      rtc0
  9:          0          0   IO-APIC-fasteoi   acpi
 16:     609652          0   IO-APIC-fasteoi   uhci_hcd:usb1, heci
 17:          0          0   IO-APIC-fasteoi   pata_marvell
 18:      33141          0   IO-APIC-fasteoi   sata_promise, uhci_hcd:usb5, ehci_hcd:usb6
 19:          0          0   IO-APIC-fasteoi   uhci_hcd:usb4
 21:   15985105          0   IO-APIC-fasteoi   uhci_hcd:usb2, ath
 23:    8730160          0   IO-APIC-fasteoi   uhci_hcd:usb3, ehci_hcd:usb7
 29:    1855556          0   PCI-MSI-edge      i915
 30:    1109316          0   PCI-MSI-edge      ahci
 31:      66952          0   PCI-MSI-edge      e1000
NMI:          0          0   Non-maskable interrupts
LOC:   14417376   16273096   Local timer interrupts
SPU:          0          0   Spurious interrupts
RES:     150950     182106   Rescheduling interrupts
CAL:        278        611   Function call interrupts
TLB:      33349      53705   TLB shootdowns
TRM:          0          0   Thermal event interrupts
THR:          0          0   Threshold APIC interrupts
ERR:          0
MIS:          0
[recombinator](0) $

ACPI

  • The MADT table can supply multiprocessor configuration
  • MP Table
  • Interactions with cpuid
  • HyperThreading (Intel SMT) requires CPU, BIOS and OS support. Introduced on the P4.
    • Found on (all) i7's, some Atoms, and some P4's and Core2Duo's (especially those with Xeon branding).
    • Pentium-M and Celerons usually lack SMT.

/proc/cpuinfo

On Linux kernels with the proc filesystem enabled (and FreeBSD kernels with the linprocfs module loaded, although this does not provide all of the information as native Linux /proc/cpuinfo), the mounted proc/linprocfs filesystem contains a file cpuinfo (this is independent of any CPU-related modules being loaded, particularly cpuid on Linux or either OS's cpu module). Interpreting this file, as it pertains to multiple execution units, can be difficult. The following applies to Linux 2.6 kernels:

  • A physical_id corresponds to a socket ("physical package"), of which there are >=1 per machine. Physical IDs do not necessarily monotonically increase across processors, and thus the maximum physical_id does not by itself determine the number of sockets!
  • A core_id corresponds to a core ("logical processor"), of which there are >=1 per physical_id
  • A processor ID corresponds to an architectural state (HyperThreading == 2 per HyperThreaded core)
  • HyperThreading is in use only if 'siblings' != 'cpu cores' (from http://kbase.redhat.com/faq/FAQ_46_10715.shtm)
  • The 'ht' processor capabilities bit corresponds not to HyperThreading, but to the ability to report sibling count

Examples

I've removed all output from the following examples, save that related to SMP identification.

  • EMT64 Xeon, no HyperThreading support, 4 cores per socket, 4 sockets: 16 total execution units (2.6.26) (Dell R900)
[wopr](0) $ cat /proc/cpuinfo | egrep ^proc\|^model\ \|^phys\|^sib\|^core\|^cpu\ c\|^ap\|^init
processor	: 0
model name	: Intel(R) Xeon(R) CPU           X7350  @ 2.93GHz
physical id	: 0
siblings	: 4
core id		: 0
cpu cores	: 4
apicid		: 0
initial apicid	: 0

processor	: 1
model name	: Intel(R) Xeon(R) CPU           X7350  @ 2.93GHz
physical id	: 2
siblings	: 4
core id		: 0
cpu cores	: 4
apicid		: 8
initial apicid	: 8

processor	: 2
model name	: Intel(R) Xeon(R) CPU           X7350  @ 2.93GHz
physical id	: 4
siblings	: 4
core id		: 0
cpu cores	: 4
apicid		: 16
initial apicid	: 16

processor	: 3
model name	: Intel(R) Xeon(R) CPU           X7350  @ 2.93GHz
physical id	: 6
siblings	: 4
core id		: 0
cpu cores	: 4
apicid		: 24
initial apicid	: 24

processor	: 4
model name	: Intel(R) Xeon(R) CPU           X7350  @ 2.93GHz
physical id	: 0
siblings	: 4
core id		: 2
cpu cores	: 4
apicid		: 2
initial apicid	: 2

processor	: 5
model name	: Intel(R) Xeon(R) CPU           X7350  @ 2.93GHz
physical id	: 2
siblings	: 4
core id		: 2
cpu cores	: 4
apicid		: 10
initial apicid	: 10

processor	: 6
model name	: Intel(R) Xeon(R) CPU           X7350  @ 2.93GHz
physical id	: 4
siblings	: 4
core id		: 2
cpu cores	: 4
apicid		: 18
initial apicid	: 18

processor	: 7
model name	: Intel(R) Xeon(R) CPU           X7350  @ 2.93GHz
physical id	: 6
siblings	: 4
core id		: 2
cpu cores	: 4
apicid		: 26
initial apicid	: 26

processor	: 8
model name	: Intel(R) Xeon(R) CPU           X7350  @ 2.93GHz
physical id	: 0
siblings	: 4
core id		: 1
cpu cores	: 4
apicid		: 1
initial apicid	: 1

processor	: 9
model name	: Intel(R) Xeon(R) CPU           X7350  @ 2.93GHz
physical id	: 2
siblings	: 4
core id		: 1
cpu cores	: 4
apicid		: 9
initial apicid	: 9

processor	: 10
model name	: Intel(R) Xeon(R) CPU           X7350  @ 2.93GHz
physical id	: 4
siblings	: 4
core id		: 1
cpu cores	: 4
apicid		: 17
initial apicid	: 17

processor	: 11
model name	: Intel(R) Xeon(R) CPU           X7350  @ 2.93GHz
physical id	: 6
siblings	: 4
core id		: 1
cpu cores	: 4
apicid		: 25
initial apicid	: 25

processor	: 12
model name	: Intel(R) Xeon(R) CPU           X7350  @ 2.93GHz
physical id	: 0
siblings	: 4
core id		: 3
cpu cores	: 4
apicid		: 3
initial apicid	: 3

processor	: 13
model name	: Intel(R) Xeon(R) CPU           X7350  @ 2.93GHz
physical id	: 2
siblings	: 4
core id		: 3
cpu cores	: 4
apicid		: 11
initial apicid	: 11

processor	: 14
model name	: Intel(R) Xeon(R) CPU           X7350  @ 2.93GHz
physical id	: 4
siblings	: 4
core id		: 3
cpu cores	: 4
apicid		: 19
initial apicid	: 19

processor	: 15
model name	: Intel(R) Xeon(R) CPU           X7350  @ 2.93GHz
physical id	: 6
siblings	: 4
core id		: 3
cpu cores	: 4
apicid		: 27
initial apicid	: 27
[wopr](0) $
  • Core 2 Duo, no HyperThreading support, 2 cores per socket, 1 socket: 2 total execution units (2.6.26)
[recombinator](0) $ cat /proc/cpuinfo 
processor	: 0
model name	: Intel(R) Core(TM)2 CPU          6600  @ 2.40GHz
physical id	: 0
siblings	: 2
core id		: 0
cpu cores	: 2
apicid		: 0
initial apicid	: 0

processor	: 1
model name	: Intel(R) Core(TM)2 CPU          6600  @ 2.40GHz
physical id	: 0
siblings	: 2
core id		: 1
cpu cores	: 2
apicid		: 1
initial apicid	: 1
[recombinator](0) $

==libvirt==

  • virsh(1)'s nodeinfo command can be pretty useful:
[wopr](0) $ virsh nodeinfo
CPU model:           x86_64
CPU(s):              16
CPU frequency:       1600 MHz
CPU socket(s):       4
Core(s) per socket:  4
Thread(s) per core:  1
NUMA cell(s):        1
Memory size:         66113480 kB

*P4 Xeon, HyperThreading enabled, 1 core per socket, 2 sockets: 4 total execution units (2.6.25-2-686)
<pre>scurdev@hrududu:~$ cat /proc/cpuinfo 
processor	: 0
model name	: Intel(R) Xeon(TM) CPU 2.40GHz
physical id	: 0
siblings	: 2
core id		: 0
cpu cores	: 1

processor	: 1
model name	: Intel(R) Xeon(TM) CPU 2.40GHz
physical id	: 0
siblings	: 2
core id		: 0
cpu cores	: 1

processor	: 2
model name	: Intel(R) Xeon(TM) CPU 2.40GHz
physical id	: 3
siblings	: 2
core id		: 0
cpu cores	: 1

processor	: 3
model name	: Intel(R) Xeon(TM) CPU 2.40GHz
physical id	: 3
siblings	: 2
core id		: 0
cpu cores	: 1
scurdev@hrududu:~$
  • P4 Xeon, HyperThreading disabled, 1 core per socket, 2 sockets: 2 total execution units (2.6.25-2-686)
[aho](0) $ cat /proc/cpuinfo 
processor	: 0
model name	: Intel(R) Xeon(TM) CPU 2.80GHz

processor	: 1
model name	: Intel(R) Xeon(TM) CPU 2.80GHz
[aho](0) $
  • P4 Xeon Celeron, HyperThreading disabled, 1 core per socket, 1 socket: 1 total execution unit (2.6.25-2-686)
[knuth](0) $ cat /proc/cpuinfo 
processor	: 0
model name	: Intel(R) Celeron(R) CPU 2.00GHz
[knuth](0) $

Sysctl

On FreeBSD, CPU/SMP information is primarily exported through the sysctl(8) interface. Seemingly relevant sysctls are listed below:

  • kern.smp.cpus and hw.ncpu
  • machdep.hyperthreading.allowed
  • kern.threads.virtual_cpu

libvirt

  • virsh(1)'s nodeinfo command can be pretty useful:
[wopr](0) $ virsh nodeinfo
CPU model:           x86_64
CPU(s):              16
CPU frequency:       1600 MHz
CPU socket(s):       4
Core(s) per socket:  4
Thread(s) per core:  1
NUMA cell(s):        1
Memory size:         66113480 kB
[wopr](0) $ 
[recombinator](0) $ sudo virsh nodeinfo
CPU model:           x86_64
CPU(s):              2
CPU frequency:       1596 MHz
CPU socket(s):       1
Core(s) per socket:  2
Thread(s) per core:  1
NUMA cell(s):        1
Memory size:         3908568 kB

[recombinator](0) $


See also

  • This LKML thread provides much information
  • The [cpuid] instruction can interrogate each processing unit
Retrieved from "https://nick-black.com/dankwiki/index.php?title=SMP_on_x86&oldid=925"