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Revision 94a420b1

ID94a420b170b3e997a185a4148accc87bdcd18156

Added by Stefan Hajnoczi almost 11 years ago

trace: Add trace-events file for declaring trace events

This patch introduces the trace-events file where trace events can be
declared like so:

qemu_malloc(size_t size) "size %zu"
qemu_free(void *ptr) "ptr %p"

These trace event declarations are processed by a new tool called
tracetool to generate code for the trace events. Trace event
declarations are independent of the backend tracing system (LTTng User
Space Tracing, ftrace markers, DTrace).

The default "nop" backend generates empty trace event functions.
Therefore trace events are disabled by default.

The trace-events file serves two purposes:

1. Adding trace events is easy. It is not necessary to understand the
details of a backend tracing system. The trace-events file is a
single location where trace events can be declared without code
duplication.

2. QEMU is not tightly coupled to one particular backend tracing system.
In order to support tracing across QEMU host platforms and to
anticipate new backend tracing systems that are currently maturing,
it is important to be flexible and not tied to one system.

This commit includes fixes from Prerna Saxena

 and Blue Swirl <blauwirbel@gmail.com>.

Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>

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