coupling facility cpu

© 2009 IBM Corporation 1

What's New With Coupling Facility CPU

Martin Packer

[email protected]+447802245584Twitter: MartinPacker

mailto:[email protected]

© 2009 IBM Corporation2

Abstract

Recently RMF's reporting of Coupling Facility CPU was enhanced, mainly to give more granularity.

This presentation outlines the author's experience with this important new instrumentation, both from the perspective of Capacity Planning and from the perspective of how parallel sysplexes perform under increasing load. It also covers other areas of Parallel Sysplex performance.

IN CASE YOU WERE IN ANY DOUBT: “other areas” does not mean “ALL other areas”. :-)


Topics

Structure-Level CPU

– Structure CPU Experiment

CPU / LPAR Match Up Between 70-1 and 74-4

Conclusings and Musions

© 2009 IBM Corporation 4

Structure-Level CPU


Structure-Level CPU Consumption CFLEVEL 15 and z/OS R.9

– Most customers are now this far advanced

New SMF 74-4 Field: R744SETM

– “Structure Execution Time”

Always 100% Capture Ratio

– Adds up to R744PBSY

Multiple uses:

– Capacity planning for changing request rates

– Examine which structures are large consumers

– Compute CPU cost of a request

• And compare to service time• Interesting number is “non-CPU” element of service time - as we shall see

– Understand whether CPU per request has degraded

– Estimating Structure Duplexing cost

NOTE:

– Need to collect 74-4 data from all z/OS systems sharing to get total request rate

• Otherwise “CPU per request” calculation will overestimate


Structure CPU Experiment


Structure CPU Experiment Based on

– R744SETM Structure Execution Time– Sync Request Rate

• Virtually no Async– Sync Service Time

One minute RMF intervals– Sorted by request rate increasing

Run was 1-way DB2 Datasharing– Only really active structures ISGLOCK and LOCK1

Red lines are CPU time per request– Blue lines are Service time per request

ISGLOCK “low volume”– Shows amortization of some fixed cost effect

• Wondering also if some “practice effect” affects service times– CF used IC links

LOCK1 “high volume”– More reliable for capacity planning– CF used a mixture of ISC and ICB links


ISGLOCK Requests

0

2

4

6

8

10

12

14

16

0 10 20 30 40 50 60 70

Requests / Second

Mic

rose

cond

s

CPU Time Service Time

3us?


LOCK1 Requests

0

2

4

6

8

10

12

750 800 850 900

Requests / Second

Mic

rose

cond

s

CPU Time Service Time

3.5us?


And From My Travels... Next chart isn't from the experiment just described

– A real customer system

A Group Buffer Pool

ISC-Connected

– Necessary for the customer's estate

Clearly something goes wrong at about 1100 requests / second

– Especially in response time terms but also CPU

• (Coupling Facility not CPU constrained)

Options include

– Managing the request rate to below 1100 / sec

– Working on the request mix

– Infrastructure reconfiguration


25us?


CPU / LPAR Match Up Between 701 and 744


●Managed out of Pool 5 in z9 and z10● Pool numbers given in SMF 70 as index into table of labels● Recommendation: Manage in reporting as a separate pool

●Follow special CF sizing guidelines● Especially for takeover situations

●Always runs at full speed● So good technology match for coupled z/OS images on same footprint● Another good reason to use ICFs is IC links

●Shared ICFs strongly discouraged for Production● Especially if the CF image has Dynamic Dispatch turned on

●Should not run ANY coupling facility above 50% busy● Especially if we need to be able to recover structures onto it

Internal Coupling Facility - Basics


ICF CPU Instrumentation

SMF 744 view different from SMF 701 LPAR view of processor busy•R744PBSY is CPU time processing requests•R744PWAI is CPU time while CFCC is not processing requests but it is still using CF cycles

•For Dynamic Dispatch PWAI is time when not processing CF requests but Logical CP not yet taken back by PR/SM

•For dedicated or nonDynamic Dispatch cases sum is constant•For Dynamic Dispatch sum can vary.

Number of defined processors is number of CF Processor Data sections in 744•Refined for CFLEVEL 15 by new fields for dedicated (R744FPDN) and shared (R744FPSN) processors•Also whether individual engine is dedicated (R744PTYP) and its weight (R744PWGT)

PBSY and PWAI Can be examined down to Coupling Facility engine levelSMF 744 has much more besides CF CPU instrumentation


CF LPAR Identification In SMF 70-1 Is Complex

Need to match LPARs in SMF 70-1 with coupling facilities in SMF 74-4 to get proper CPU picture

Since z/OS Release 8 74-4 has machine serial number

– Allows correlation in most cases

– But LPAR names and CF Names often don't match

– Often multiple CF's in same footprint with similar configuration

– Sometimes there are multiple CF's with the same name

– My code – in extremis – uses the presence of IC links to determine “colocality”

– I'm slowly learning :-) not all CF LPARs are in Pool 5


New Instrumentation - OA21140

Introduced to support zHPF

– Has other SMF and reporting improvements

• HiperDispatch Vertical Polarisation indicators at ENGINE level – Type 70

• Normalisation factor for zIIP – Type 70

Adds CF LPAR Partition Number

– Allows matching with SMF 70-1

RMF Level (SMFxxSRL) changed to X'55'


Conclusings and Musions

I think we've come a long way with Coupling Facility CPU

– Capacity Planning is now down to the structure level

• But not to the structure-by-system level

– We can now tie up the Coupling Facility and LPAR views of CPU

• With a few “corner cases”

I'd encourage you to revisit your Parallel Sysplex reporting

– Including for all the other aspects we didn't have time for

Shouldn't machines be self-documenting in SMF?

coupling facility cpu

Technology

ibm corporation

cpu cost

cpu coupling facility

cpu constrained options

proper cpu picture

request calculation

total request rate

request blue lines