diff options
Diffstat (limited to 'docs/devel/tracing.txt')
| -rw-r--r-- | docs/devel/tracing.txt | 12 |
1 files changed, 5 insertions, 7 deletions
diff --git a/docs/devel/tracing.txt b/docs/devel/tracing.txt index 8c0376fefa..cb5f685de9 100644 --- a/docs/devel/tracing.txt +++ b/docs/devel/tracing.txt @@ -342,8 +342,10 @@ edit the "trace-events-all" file). In addition, there might be cases where relatively complex computations must be performed to generate values that are only used as arguments for a trace -function. In these cases you can use the macro 'TRACE_${EVENT_NAME}_ENABLED' to -guard such computations and avoid its compilation when the event is disabled: +function. In these cases you can use 'trace_event_get_state_backends()' to +guard such computations, so they are skipped if the event has been either +compile-time disabled or run-time disabled. If the event is compile-time +disabled, this check will have no performance impact. #include "trace.h" /* needed for trace event prototype */ @@ -356,7 +358,7 @@ guard such computations and avoid its compilation when the event is disabled: align = getpagesize(); } ptr = qemu_memalign(align, size); - if (TRACE_QEMU_VMALLOC_ENABLED) { /* preprocessor macro */ + if (trace_event_get_state_backends(TRACE_QEMU_VMALLOC)) { void *complex; /* some complex computations to produce the 'complex' value */ trace_qemu_vmalloc(size, ptr, complex); @@ -364,10 +366,6 @@ guard such computations and avoid its compilation when the event is disabled: return ptr; } -You can check both if the event has been disabled and is dynamically enabled at -the same time using the 'trace_event_get_state_backends' routine (see header -"trace/control.h" for more information). - === "tcg" === Guest code generated by TCG can be traced by defining an event with the "tcg" |