[XenPPC] [XEN][POWERPC][PATCH 0/3] Guest Perfmon implementation

[Christian Ehrhardt <ehrhardt@xxxxxxxxxxxxxxxxxx>]

This patchset enables any domain (Dom0 and/or DomU) on xen-ppc to use 
the Performance Monitor Extensions of the Power Acrhitecture as known 
from non virtualized environments e.g. oprofile. It does this by 
implementing the back end of the H_PERFMON call in xen which is used to 
enable the Performance Monitor on non virtualized systems. Additionally 
it implements a perfmon exception handler to catch "postponed" perfmon 
exceptions from the running domains.
Known Issues of the current implementation (Should be fixed with the 
following extensions - see below):
- While a user can use any known performance monitor counter setup, xen 
currently does not know how they are used. In the case of "postponed" 
perfmon exceptions (Domain samples that are reported into xen space) xen 
has to reset the pmc counters. Xen does not know what special counters 
are currently set up in the linux guest so it uses the values ones which 
represent the oprofile default setup.
- The results of the postponed performance monitor exceptions are 
accuracy just ignored which decreases the accuracy dependent on the 
proportion between valid and postponed exceptions. Short test showed 
that this issue scales utilization dependent. An idling system had ~10 
of 400 postponed exceptions while a heavy utilized system had only 10 of 
300000. As there is an application running that is profiled in most 
scenarios the load and thereby the accuracy should be fair enough for 
this first implementation step.
If possible the following extensions should take place (Consider this as 
small plan proposal):
- Sampling xen by passing xen samples to a profiling domain (I hope this 
part can be implemented similar to the xenoprof approach).
- Passing results of postponed perfmon exceptions to the appropriate domain
- Making xen aware of each domains performance monitor counter setup to 
do reset pmc in a really "valid" way
Signed-off-by: Christian Ehrhardt <ehrhardt@xxxxxxxxxxxxxxxxxx>

The patches are taken against the tip of Friday 05/04/2007 in 
http://xenbits.xensource.com/xen-unstable.hg and 
http://xenbits.xensource.com/ext/linux-ppc-2.6.hg
It was tested in the following scenarios on a JS21:
- profiling on a single Dom0
- profiling on a single Dom0 while DomU's running
- profiling on a single DomU
- profiling on multiple DomU

Xen:
b/xen/arch/powerpc/papr/h_perfmon.c        |  155 
+++++++++++++++++++++++++++++
xen/arch/powerpc/domain.c                  |   15 ++
xen/arch/powerpc/exceptions.h              |    1
xen/arch/powerpc/of_handler/papr.S         |    2
xen/arch/powerpc/papr/Makefile             |    1
xen/arch/powerpc/powerpc64/domain.c        |   49 +++++++++
xen/arch/powerpc/powerpc64/exceptions.S    |   26 ++++
xen/include/asm-powerpc/domain.h           |   20 +++
xen/include/asm-powerpc/papr.h             |    1
xen/include/asm-powerpc/powerpc64/config.h |    2
xen/include/asm-powerpc/processor.h        |  137 +++++++++++++++++++++++++
xen/include/asm-powerpc/reg_defs.h         |   28 +++++
xen/include/asm-powerpc/xenoprof.h         |   83 +++++++++++++++
13 files changed, 516 insertions(+), 4 deletions(-)

Linux:
setup.c |   14 ++++++++++++++
1 files changed, 14 insertions(+)

--

Grüsse / regards, 
Christian Ehrhardt
IBM Linux Technology Center, Open Virtualization
+49 7031/16-3385
Ehrhardt@xxxxxxxxxxxxxxxxxxx
Ehrhardt@xxxxxxxxxx

IBM Deutschland Entwicklung GmbH
Vorsitzender des Aufsichtsrats: Johann Weihen 
Geschäftsführung: Herbert Kircher 
Sitz der Gesellschaft: Böblingen
Registergericht: Amtsgericht Stuttgart, HRB 243294


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