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powerpc: tracing: Add hypervisor call tracepoints

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Add hcall_entry and hcall_exit tracepoints.  This replaces the inline
assembly HCALL_STATS code and converts it to use the new tracepoints.

To keep the disabled case as quick as possible, we embed a status word
in the TOC so we can get at it with a single load.  By doing so we
keep the overhead at a minimum.  Time taken for a null hcall:

No tracepoint code:	135.79 cycles
Disabled tracepoints:	137.95 cycles

For reference, before this patch enabling HCALL_STATS resulted in a null
hcall of 201.44 cycles!

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
This commit is contained in:
Anton Blanchard
2009-10-26 18:50:29 +00:00
committed by Paul Mackerras
parent 6795b85c6a
commit c8cd093a6e
6 changed files with 175 additions and 44 deletions
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arch/powerpc/Kconfig.debug
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@@ -46,7 +46,7 @@ config DEBUG_STACK_USAGE
config HCALL_STATS
bool "Hypervisor call instrumentation"
depends on PPC_PSERIES && DEBUG_FS
depends on PPC_PSERIES && DEBUG_FS && TRACEPOINTS
help
Adds code to keep track of the number of hypervisor calls made and
the amount of time spent in hypervisor calls. Wall time spent in