trace: always compile support for controlling and querying trace event states
The current interface is generic for this small set of operations, and thus other backends can easily modify the "trace/control.c" file to add their own implementation. Signed-off-by: Lluís Vilanova <vilanova@ac.upc.edu>
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Lluís
Stefan Hajnoczi
parent
fc76410539
commit
31965ae27b
@ -108,6 +108,36 @@ portability macros, ensure they are preceded and followed by double quotes:
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of trace events. Marking trace events disabled by default saves the user
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from having to manually disable noisy trace events.
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== Generic interface and monitor commands ==
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You can programmatically query and control the dynamic state of trace events
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through a backend-agnostic interface:
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* trace_print_events
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* trace_event_set_state
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Enables or disables trace events at runtime inside QEMU.
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The function returns "true" if the state of the event has been successfully
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changed, or "false" otherwise:
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#include "trace/control.h"
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trace_event_set_state("virtio_irq", true); /* enable */
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[...]
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trace_event_set_state("virtio_irq", false); /* disable */
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Note that some of the backends do not provide an implementation for this
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interface, in which case QEMU will just print a warning.
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This functionality is also provided through monitor commands:
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* info trace-events
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View available trace events and their state. State 1 means enabled, state 0
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means disabled.
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* trace-event NAME on|off
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Enable/disable a given trace event.
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== Trace backends ==
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The "tracetool" script automates tedious trace event code generation and also
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@ -157,27 +187,9 @@ unless you have specific needs for more advanced backends.
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flushed and emptied. This means the 'info trace' will display few or no
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entries if the buffer has just been flushed.
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* info trace-events
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View available trace events and their state. State 1 means enabled, state 0
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means disabled.
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* trace-event NAME on|off
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Enable/disable a given trace event.
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* trace-file on|off|flush|set <path>
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Enable/disable/flush the trace file or set the trace file name.
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==== Enabling/disabling trace events programmatically ====
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The st_change_trace_event_state() function can be used to enable or disable trace
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events at runtime inside QEMU:
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#include "trace.h"
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st_change_trace_event_state("virtio_irq", true); /* enable */
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[...]
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st_change_trace_event_state("virtio_irq", false); /* disable */
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==== Analyzing trace files ====
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The "simple" backend produces binary trace files that can be formatted with the
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@ -180,7 +180,6 @@ STEXI
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Output logs to @var{filename}.
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ETEXI
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#ifdef CONFIG_TRACE_SIMPLE
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{
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.name = "trace-event",
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.args_type = "name:s,option:b",
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@ -195,6 +194,7 @@ STEXI
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changes status of a trace event
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ETEXI
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#if defined(CONFIG_SIMPLE_TRACE)
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{
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.name = "trace-file",
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.args_type = "op:s?,arg:F?",
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@ -1358,11 +1358,14 @@ ETEXI
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STEXI
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@item info trace
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show contents of trace buffer
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@item info trace-events
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show available trace events and their state
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ETEXI
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#endif
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STEXI
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@item info trace-events
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show available trace events and their state
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ETEXI
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STEXI
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@end table
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ETEXI
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@ -57,8 +57,9 @@
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#include "json-parser.h"
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#include "osdep.h"
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#include "cpu.h"
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#include "trace/control.h"
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#ifdef CONFIG_TRACE_SIMPLE
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#include "trace.h"
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#include "trace/simple.h"
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#endif
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#include "trace/control.h"
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#include "ui/qemu-spice.h"
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@ -593,7 +594,6 @@ static void do_help_cmd(Monitor *mon, const QDict *qdict)
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help_cmd(mon, qdict_get_try_str(qdict, "name"));
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}
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#ifdef CONFIG_TRACE_SIMPLE
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static void do_trace_event_set_state(Monitor *mon, const QDict *qdict)
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{
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const char *tp_name = qdict_get_str(qdict, "name");
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@ -605,6 +605,7 @@ static void do_trace_event_set_state(Monitor *mon, const QDict *qdict)
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}
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}
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#ifdef CONFIG_SIMPLE_TRACE
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static void do_trace_file(Monitor *mon, const QDict *qdict)
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{
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const char *op = qdict_get_try_str(qdict, "op");
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@ -1002,12 +1003,12 @@ static void do_info_trace(Monitor *mon)
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{
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st_print_trace((FILE *)mon, &monitor_fprintf);
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}
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#endif
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static void do_trace_print_events(Monitor *mon)
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{
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trace_print_events((FILE *)mon, &monitor_fprintf);
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}
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#endif
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/**
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* do_quit(): Quit QEMU execution
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@ -3144,6 +3145,7 @@ static const mon_cmd_t info_cmds[] = {
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.help = "show current contents of trace buffer",
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.mhandler.info = do_info_trace,
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},
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#endif
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{
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.name = "trace-events",
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.args_type = "",
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@ -3151,7 +3153,6 @@ static const mon_cmd_t info_cmds[] = {
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.help = "show available trace-events & their state",
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.mhandler.info = do_trace_print_events,
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},
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#endif
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{
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.name = NULL,
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},
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