powerpc: tracing: Add hypervisor call tracepoints
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>
diff --git a/arch/powerpc/Kconfig.debug b/arch/powerpc/Kconfig.debug
index 3b10051..bf3382f 100644
--- a/arch/powerpc/Kconfig.debug
+++ b/arch/powerpc/Kconfig.debug
@@ -46,7 +46,7 @@
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