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/platforms/pseries/lpar.c b/arch/powerpc/platforms/pseries/lpar.c
index 903eb9e..4b7b6e8 100644
--- a/arch/powerpc/platforms/pseries/lpar.c
+++ b/arch/powerpc/platforms/pseries/lpar.c
@@ -39,6 +39,7 @@
#include <asm/cputable.h>
#include <asm/udbg.h>
#include <asm/smp.h>
+#include <asm/trace.h>
#include "plpar_wrappers.h"
#include "pseries.h"
@@ -661,3 +662,34 @@
EXPORT_SYMBOL(arch_free_page);
#endif
+
+#ifdef CONFIG_TRACEPOINTS
+/*
+ * We optimise our hcall path by placing hcall_tracepoint_refcount
+ * directly in the TOC so we can check if the hcall tracepoints are
+ * enabled via a single load.
+ */
+
+/* NB: reg/unreg are called while guarded with the tracepoints_mutex */
+extern long hcall_tracepoint_refcount;
+
+void hcall_tracepoint_regfunc(void)
+{
+ hcall_tracepoint_refcount++;
+}
+
+void hcall_tracepoint_unregfunc(void)
+{
+ hcall_tracepoint_refcount--;
+}
+
+void __trace_hcall_entry(unsigned long opcode)
+{
+ trace_hcall_entry(opcode);
+}
+
+void __trace_hcall_exit(long opcode, unsigned long retval)
+{
+ trace_hcall_exit(opcode, retval);
+}
+#endif