nmon, TOPAS and vmstat showing incorrect CPUs

[jpor2003]

Hi Gurus,

I hope this one hasn't come up before, but we have a P570 rack running a number of LPARs. I have dynamically removed 1x CPU from 1 LPAR and added 1x CPU to another.
For example LPAR 1 had 3 CPUS now 2. When you run the following commands:

lparstat, vmstat, topas these currently show as 8 CPUs. When you check this with either:

prtconf |grep -i proc
lsdev -Cc processor

or look at the ODM entry by using:

odmget -q "value=PowerPC_POWER5" CuAt

These all report the correct CPU at being at 2.

Anyone any ideas?

Thanks.

 

[p5wizard]

logical vs physical CPUs?

show output of lparstat, vmstat and lsdev -Cc processor please...


HTH,

p5wizard

 

[jpor2003]

Hi P5wizard,

Information you have requested:

lparstat

System configuration: type=Shared mode=Capped smt=On lcpu=4 mem=16128 psize=10 ent=2.00

%user %sys %wait %idle physc %entc lbusy vcsw phint
----- ---- ----- ----- ----- ----- ------ ---- -----
0.3 0.1 0.3 99.3 0.01 0.4 4.5 211420460 1858768

vmstat

System configuration: lcpu=4 mem=16128MB ent=2.00

kthr memory page faults cpu
----- ----------- ------------------------ ------------ -----------------------
r b avm fre re pi po fr sr cy in sy cs us sy id wa pc ec
3 1 1198590 538710 0 0 0 10 27 0 202 9539 1258 0 0 99 0 0.01 0.4

lsdev -Cc processor

proc0 Available 00-00 Processor
proc2 Available 00-02 Processor

And as a bonus odmget -q "value=PowerPC_POWER5" CuAt

CuAt:
name = "proc2"
attribute = "type"
value = "PowerPC_POWER5"
type = "R"
generic = "D"
rep = "sl"
nls_index = 49

CuAt:
name = "proc0"
attribute = "type"
value = "PowerPC_POWER5"
type = "R"
generic = "D"
rep = "sl"
nls_index = 49

 

[MoreFeo]

You've got 2 physical processors (proc0 and proc2), but with SMT activated AIX sees 4 logical CPUs.

lparstat en vmstat shows 4 lcpu (logical cpu) and 2 as ent (entitled capacity = number of physical procs).

lsdev -Cc processor and the ODM also shows the 2 physical procs.

 

[jpor2003]

Hi Morfeo,

This issue has only cropped up due to some application testers checking the performance of the LPAR. Whilst running some applications they use the tools AIX provides.

I take SMT is basically what you find on INTEL HT CPUS? I.e a form of hyperthreading that makes the 1 CPU act as 2?

 

[MoreFeo]

Yes, SMT is Simultaneous Multi-Threading, and if enabled the operating system thinks he's got 2 CPUs per proc.

 

[p5wizard]

MoreFeo beat me to it - I was out to lunch...

Where do you get 8 CPUs? (This I read in your OP)


HTH,

p5wizard

 

[MoreFeo]

I was also looking for 8 CPUs, but just found 4.

 

[jpor2003]

Sorry guys. The example I gave you was from another box I had up and running at the time, which also was being used for performance testing. The 8CPU one I first mentioned was from a 4xCPU LPAR nad had the SMT enabled. But the answers you gave me came in handy.

Thanks to all that replied.