6. DATA SOURCES › 6.8 PR/SM LPAR Concepts › 6.8.5 Data Analysis › 6.8.5.2 LPAR Level Analysis › 6.8.5.2.2 Special Purpose LPARs › 6.8.5.2.2.2 Integrated Facilities for Linux
6.8.5.2.2.2 Integrated Facilities for Linux
The Integrated Facility for Linux (IFL) is a specialized
processor unit devoted exclusively to Linux workloads. It
can run either a single Linux image under the Linux operating
system, or multiple Linux images under the control of z/VM
Version 4 and higher, in an LPAR operating in Linux-Only
mode.
As for internal coupling facilities, LPARs configured with
IFLs do not run RMF; therefore, their utilization statistics
are limited. The SMF records created by RMF do not provide
any information from inside Linux, and PR/SM is only aware of
the total amount of time the special purpose processors
assigned to these LPARs were dispatched.
Depending on your data center's requirements, IFLs may be
configured as either dedicated or shared:
Dedicated IFLs
--------------
Dedicated IFLs are considered by PR/SM as always dispatched.
Therefore, the dispatch time is equal to the measurement
interval time, regardless of actual processor utilization;
and the LPAR appears as being used 100% of the time in the
HARLPC file.
Shared IFLs Only
----------------
When an LPAR is configured with shared IFLs, that LPAR should
not appear as being 100% busy anymore in the HARLPC file. It
should report the actual amount of time PR/SM allocated to
its operating system.
Data Elements Related to IFL Activity
-------------------------------------
The following data elements help you to identify and report
on IFLs. Please refer to their data dictionary entries for
more detailed information, such as how they are used in the
computation of derived data elements.
o From the HARVPA file:
- PRSMPRTP: Logical Processor Type
This element identifies the pool of processors
to which a logical processor belongs. For
zSeries and earlier models, IFLs belong to the
generic ICF processors' pool, thus they have a
value of ICF in PRSMPRTP. Use CPUTYPE
described below to accurately identify IFLs.
For System z9 and later models, the value of
PRSMPRTP is IFL.
- CPUTYPE: Physical Engine Type
Integrated facilities for Linux are identified
by a value of IFL in this element (other
possible values are CP, ICF, IFA, and IIP).
Subsetting or summarizing the HARVPA
information by this data element allows you to
isolate statistics only pertaining to IFLs.
Note that, for System z9 and later models,
CPUTYPE contains the same value as PRSMPRTP.
o From the HARLPC file:
- PRSMLPTP: Logical Partition Type
Linux-only logical partitions using IFLs are
identified by the value of ICF in this data
element. However, they are not the only type
of LPAR in this category, which also includes
CF LPARs configured with ICFs. Therefore, when
using PRSMLPTP for subsetting or summarizing
HARLPC data, be careful to use your
configuration knowledge to select only Linux
LPARs.
- LPCTIDTM: Total ICF Processors Dispatch Time (zSeries)
LPCTNDTM: Total IFL Processors Dispatch Time (z9)
For an LPAR using dedicated IFLs, this element
will be very close to the interval duration
(DURATION). If the LPAR uses shared IFLs, it
will vary according to the LPAR's weight, and
the actual system load.
- LPCTODTM: Total CP Processors Dispatch Time
For an LPAR using IFLs, this element will
always be equal to zero.
- LPCSIDTM: Total Shared ICF Proc. Dispatch Time (zSeries)
LPCSNDTM: Total Shared IFL Proc. Dispatch Time (z9)
For an LPAR using dedicated IFLs, this element
will be equal to zero.
For an LPAR using shared IFLs, this element
will be equal to LPCTIDTM (or LPCTNDTM for z9
and later models), since all resources used by
the LPAR are from the shared pool.
