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Diffstat (limited to 'docs/tracing.txt')
| -rw-r--r-- | docs/tracing.txt | 48 |
1 files changed, 30 insertions, 18 deletions
diff --git a/docs/tracing.txt b/docs/tracing.txt index 1ad106a5d7..41eb8e6fec 100644 --- a/docs/tracing.txt +++ b/docs/tracing.txt @@ -108,6 +108,36 @@ portability macros, ensure they are preceded and followed by double quotes: of trace events. Marking trace events disabled by default saves the user from having to manually disable noisy trace events. +== Generic interface and monitor commands == + +You can programmatically query and control the dynamic state of trace events +through a backend-agnostic interface: + +* trace_print_events + +* trace_event_set_state + Enables or disables trace events at runtime inside QEMU. + The function returns "true" if the state of the event has been successfully + changed, or "false" otherwise: + + #include "trace/control.h" + + trace_event_set_state("virtio_irq", true); /* enable */ + [...] + trace_event_set_state("virtio_irq", false); /* disable */ + +Note that some of the backends do not provide an implementation for this +interface, in which case QEMU will just print a warning. + +This functionality is also provided through monitor commands: + +* info trace-events + View available trace events and their state. State 1 means enabled, state 0 + means disabled. + +* trace-event NAME on|off + Enable/disable a given trace event. + == Trace backends == The "tracetool" script automates tedious trace event code generation and also @@ -157,27 +187,9 @@ unless you have specific needs for more advanced backends. flushed and emptied. This means the 'info trace' will display few or no entries if the buffer has just been flushed. -* info trace-events - View available trace events and their state. State 1 means enabled, state 0 - means disabled. - -* trace-event NAME on|off - Enable/disable a given trace event. - * trace-file on|off|flush|set <path> Enable/disable/flush the trace file or set the trace file name. -==== Enabling/disabling trace events programmatically ==== - -The st_change_trace_event_state() function can be used to enable or disable trace -events at runtime inside QEMU: - - #include "trace.h" - - st_change_trace_event_state("virtio_irq", true); /* enable */ - [...] - st_change_trace_event_state("virtio_irq", false); /* disable */ - ==== Analyzing trace files ==== The "simple" backend produces binary trace files that can be formatted with the |