With the PA-8800s and other dual-core processors,
there are two CPUs per socket. (On a cell board with four sockets,
this allows 8 CPUs per cell board.) The CPUs that share the socket
are called sibling CPUs.
Splitting sibling CPUs across
virtual partitions refers to assigning one sibling CPU to one partition
and assigning the other sibling CPU to a different virtual partition.
No noticeable performance degradation has been seen when splitting
sibling CPUs. Due to items such as the larger L2 cache size, there
actually can be a small performance boost if the siblings are split
such that one of the virtual partitions has no workload. If you require
consistently predictable performance, configure the virtual partitions
consistently; in other words, decide whether to split siblings or
keep them together, and maintain that policy across all virtual partitions.
Determining If the System Has Dual-Core Processors |
 |
You can see the sibling and virtual partition
assignment using vparstatus -d. If you do not have
a dual-core system, the output will show dashes (-) for the sibling
and assignment information:
# vparstatus -d
CPU Cell Config Sibling Information
path CPU HPA ID Status Assigned to Path /vPar name
===== ================== ==== ====== ================== =======================
0.10 0xfffffffffc078000 0 E vpuma02 - -
0.11 0xfffffffffc07a000 0 E vpuma01 - -
0.12 0xfffffffffc07c000 0 E vpuma04 - -
0.13 0xfffffffffc07e000 0 E - - -
... |
When you do have dual-core system, the vparstatus -d output will look similar to the following:
# vparstatus -d
CPU Cell Config Sibling Information
path CPU HPA ID Status Assigned to Path /vPar name
===== ================== ==== ====== ================== =======================
0.10 0xfffffffffc070000 0 E vpkeira1 0.11 vpkeira3
0.11 0xfffffffffc071000 0 E vpkeira3 0.10 vpkeira1
0.12 0xfffffffffc074000 0 E - 0.13 vpkeira4
0.13 0xfffffffffc075000 0 E vpkeira4 0.12 -
0.14 0xfffffffffc078000 0 E - 0.15 -
0.15 0xfffffffffc079000 0 E - 0.14 -
... |
You can also use the parstatus command or parmgr to determine if you are running
dual-core processors. If the maximum number of CPUs per cell is 8,
then you are running dual-core processors:
# parstatus -c 0
[Cell]
CPU Memory Use
OK/ ( GB) Core On
Hardware Actual Deconf/ OK/ Cell Next Par
Location Usage Max Deconf Connected To Capable Boot Num
========== ============ ======= ========= =================== ======= ==== ===
cab0,cell0 active core 8/0/8 2.0/ 0.0 cab0,bay0,chassis0 yes yes 0 |
Determining Sibling CPUs |
|
Once you have determined that you have a dual-core
system, the siblings have adjacent hardware paths. The first core’s
path ends in an even number, and its sibling’s path ends in
the following (odd) number. For example, if the ioscan output shows:
0/10 processor Processor
0/11 processor Processor
0/12 processor Processor
0/13 processor Processor
0/14 processor Processor
0/15 processor Processor
0/16 processor Processor
0/17 processor Processor |
The hardware paths for the sibling pairs are:
0/10 and 0/11
0/12 and 0/13
0/14 and 0/15
0/16 and 0/17 |
After vPars is installed, you can also use the
vPars Monitor’s scan command
to show hardware paths.
|
MON> scan
0 CELL sv_model=172 HPA=0xfffffffffc000000 VPAR=ALL
0/0 BUSCONV sv_model= 12 HPA=0xffffff8020000000 VPAR=ALL
0/0/0 BUS_BRIDGE sv_model= 10 HPA=0xffffff8010000000 VPAR=vpar1
0/0/1 BUS_BRIDGE sv_model= 10 HPA=0xffffff8010002000 VPAR=vpar1
0/0/2 BUS_BRIDGE sv_model= 10 HPA=0xffffff8010004000 VPAR=NONE
0/0/4 BUS_BRIDGE sv_model= 10 HPA=0xffffff8010008000 VPAR=NONE
0/0/6 BUS_BRIDGE sv_model= 10 HPA=0xffffff801000c000 VPAR=NONE
0/0/8 BUS_BRIDGE sv_model= 10 HPA=0xffffff8010010000 VPAR=vpar4
0/0/10 BUS_BRIDGE sv_model= 10 HPA=0xffffff8010014000 VPAR=vpar2
0/0/12 BUS_BRIDGE sv_model= 10 HPA=0xffffff8010018000 VPAR=NONE
0/0/14 BUS_BRIDGE sv_model= 10 HPA=0xffffff801001c000 VPAR=vpar3
0/5 MEMORY sv_model= 9 HPA=0xfffffffffc016000 VPAR=ALL
0/10 NPROC sv_model= 4 HPA=0xfffffffffc070000 VPAR=vpar2
0/11 NPROC sv_model= 4 HPA=0xfffffffffc071000 VPAR=vpar3
0/14 NPROC sv_model= 4 HPA=0xfffffffffc078000 VPAR=vpar4
0/15 NPROC sv_model= 4 HPA=0xfffffffffc079000 VPAR=SHARED
1 CELL sv_model=172 HPA=0xfffffffffc080000 VPAR=ALL
1/0 BUSCONV sv_model= 12 HPA=0xffffff8120000000 VPAR=ALL
1/0/0 BUS_BRIDGE sv_model= 10 HPA=0xffffff8110000000 VPAR=vpar1
1/0/1 BUS_BRIDGE sv_model= 10 HPA=0xffffff8110002000 VPAR=vpar1
1/0/2 BUS_BRIDGE sv_model= 10 HPA=0xffffff8110004000 VPAR=vpar4
1/0/4 BUS_BRIDGE sv_model= 10 HPA=0xffffff8110008000 VPAR=NONE
1/0/6 BUS_BRIDGE sv_model= 10 HPA=0xffffff811000c000 VPAR=vpar2
1/0/8 BUS_BRIDGE sv_model= 10 HPA=0xffffff8110010000 VPAR=NONE
1/0/10 BUS_BRIDGE sv_model= 10 HPA=0xffffff8110014000 VPAR=vpar3
1/0/12 BUS_BRIDGE sv_model= 10 HPA=0xffffff8110018000 VPAR=vpar1
1/0/14 BUS_BRIDGE sv_model= 10 HPA=0xffffff811001c000 VPAR=NONE
1/5 MEMORY sv_model= 9 HPA=0xfffffffffc096000 VPAR=ALL
1/6 IPMI sv_model=192 HPA=0xfffffffc300c0000 VPAR=ALL
1/10 NPROC sv_model= 4 HPA=0xfffffffffc0f0000 VPAR=vpar1
1/11 NPROC sv_model= 4 HPA=0xfffffffffc0f1000 VPAR=SHARED
1/14 NPROC sv_model= 4 HPA=0xfffffffffc0f8000 VPAR=SHARED
1/15 NPROC sv_model= 4 HPA=0xfffffffffc0f9000 VPAR=SHARED |
|
where the following CPU pairs are siblings:
CPU 1/10 (owned by vpar1)
and CPU 1/11 (unassigned)
CPU 0/10 (owned by vpar2)
and CPU 0/11 (owned by vpar3)
CPU 0/14 (owned by vpar4)
and CPU 0/15 (unassigned)
CPU 1/14 (unassigned) and CPU 1/15 (unassigned)
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