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54 IBM System p5 520 and 520Q Technical Overview and Introduction
Figure 2-14 Logical, virtual, and physical processor mapping
In Figure 2-14, a system with four physical processors and four partitions is presented; one
partition (LPAR4) is in dedicated mode and three partitions (LPAR1, LPAR2, and LPAR3) are
running in shared mode. Dedicated mode LPAR4 is using one physical processor and, thus,
three processors are available for shared processor pool. The LPAR1 defines five virtual
processors and the simultaneous multithreading feature is on (thus, it sees 10 logical
processors). LPAR2 defines one virtual processor and simultaneous multithreading is off (one
logical processor). LPAR3 defines two virtual processors and simultaneous multithreading is
on. Currently (sample time), virtual processors 2 and 3 of LPAR1 and virtual processor 0 of
LPAR2 are dispatched on physical processors in the shared pool. Other virtual processors
are idle waiting for dispatch by the Hypervisor. When more virtual processors are defined
within a partition, any virtual processors share equal parts of the partition processing
entitlement.
2.12.3 Virtual I/O Server
The Virtual I/O Server (VIOS) is a special purpose partition that provides virtual I/O resources
to other partitions. The Virtual I/O Server owns the physical resources (actually SCSI, Fibre
Channel and network adapters, and optical devices) and allows client partitions to share
access to them, thus, minimizing the number of physical adapters in the system. The Virtual
I/O Server eliminates the requirement that every partition own a dedicated network adapter,
disk adapter, and disk drive.
Figure 2-15 on page 55 shows an organization view of a micro-partitioned system including
the Virtual I/O Server. The figure also includes virtual SCSI and Ethernet connections and
mixed operating system partitions.
physical
CPU
(proc0)
physical
CPU
(proc1)
LPAR1 -
shared mode
5 virual CPU's
SMT ON
shared pool
virtual
processor
(VP0)
logical CPU 0
logical CPU 1
virtual
processor
(VP1)
logical CPU 2
logical CPU 3
virtual
processor
(VP2)
logical CPU 4
logical CPU 5
virtual
processor
(VP3)
logical CPU 6
logical CPU 7
virtual
processor
(VP4)
logical CPU 8
logical CPU 9
physical
CPU
(proc2)
virtual
processor
(VP0)
logical CPU 0
logical CPU 1
virtual
processor
(VP1)
logical CPU 2
logical CPU 3
physical
CPU
(proc3)
dedicated
HW - physical resources driven by Hypervisor
LPAR3 -
shared mode
2 virual CPU's
SMT ON
LPAR2 -
shared mode
1 virual CPU
SMT OFF
LPAR4 -
dedicated
1 physical CPU
SMT ON
.
allways
dispatched
physical level virtual level
OS level - operating
sytem (AIX, Linux) only
sees logical processors
virtual
processor
(VP0)
logical CPU 0
logical CPU 0
logical CPU 1
LPAR1
VP0
LP0+1
LPAR1
VP2
LP4+5
LPAR1
VP3
LP6+7
LPAR1
VP2
LP2+3
LPAR2
VP0
LP0
LPAR3
VP0
LP0+1
LPAR3
VP0
LP0+1
LPAR3
VP1
LP2+3
LPAR3
VP1
LP2+3
Spare
Processing units
Spare
Processing units
Spare
Processing units
Physical CPU proc0
Physical CPU proc1
Physical CPU proc2
0
msec
10
msec
Dispatching example with:
LPAR1 entitlement = 0.5
LPAR2 entitlement = 0.5
LPAR3 entitlement = 1.0
LPAR1
VP4
LP8+9
Spare
sample
time
dispatched dispatched dispatched