--- /dev/null
+<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
+<html>
+<head>
+ <title>LTTng User-space Tracing Design</title>
+</head>
+ <body>
+
+<h1>LTTng User-space Tracing Design</h1>
+
+<p>
+A user-space application may contain static instrumentation, and be linked with
+an associated runtime library, in order to produce an execution trace. User
+space Tracepoints and Markers, analogous to Kernel Tracepoints and Markers,
+define program locations and arguments provided. Probes may then be connected to
+each Tracepoint and Marker before they are activated. The probes will typically
+call LTTng user-space event writing functions.
+
+<p>
+When the instrumented application starts, a pipe is opened to allow external
+tracing control, asynchronous notification is requested when commands arrive in
+the pipe, and a signal handler is installed for SIGIO (or a carefully chosen
+chainable signal number). Every time such signal is received, the runtime
+library checks for commands received on the external tracing control pipe. The
+recognized commands are:
+
+<li> list the available Markers and Tracepoints;
+<li> dynamically load a library (presumably containing probes to connect);
+<li> connect a probe to a Tracepoint or Marker;
+<li> activate a Tracepoint or Marker;
+<li> initialize the tracing buffers;
+<li> flush the tracing buffers;
+<li> finalize the tracing buffers;
+
+<p>
+The application may also spontaneously provide information to the pipe:
+
+<li> a buffer is full;
+<li> new tracepoints or markers are appearing or disappearing, because modules are
+ dynamically loaded or unloaded;
+
+<p>
+In addition, the tracing control application should be notified when the
+application exits (to save the content of buffers if the application is
+crashing). Such notification may be obtained through utrace.
+<p>
+This tracing scheme plans to use a direct function call to tracing into buffers
+mapped in user-space. This should be an order of magnitude faster than the
+current Dtrace implementation (c.f.
+https://ltt.polymtl.ca/tracingwiki/index.php/DTrace) which uses a breakpoint to
+perform both dynamic and static user-space tracing. Performance comparison of
+a function call vs the int3 approach is available at
+http://sourceware.org/ml/systemtap/2006-q3/msg00793.html (see "Conclusion").
+ </body>
+</html>
+++ /dev/null
-LTTng User-space Tracing Design
-
-A user-space application may contain static instrumentation, and be linked with
-an associated runtime library, in order to produce an execution trace. User
-space Tracepoints and Markers, analogous to Kernel Tracepoints and Markers,
-define program locations and arguments provided. Probes may then be connected to
-each Tracepoint and Marker before they are activated. The probes will typically
-call LTTng user-space event writing functions.
-
-When the instrumented application starts, a pipe is opened to allow external
-tracing control, asynchronous notification is requested when commands arrive in
-the pipe, and a signal handler is installed for SIGIO (or a carefully chosen
-chainable signal number). Every time such signal is received, the runtime
-library checks for commands received on the external tracing control pipe. The
-recognized commands are:
-
-- list the available Markers and Tracepoints;
-- dynamically load a library (presumably containing probes to connect);
-- connect a probe to a Tracepoint or Marker;
-- activate a Tracepoint or Marker;
-- initialize the tracing buffers;
-- flush the tracing buffers;
-- finalize the tracing buffers;
-
-The application may also spontaneously provide information to the pipe:
-
-- a buffer is full;
-- new tracepoints or markers are appearing or disappearing, because modules are
- dynamically loaded or unloaded;
-
-In addition, the tracing control application should be notified when the
-application exits (to save the content of buffers if the application is
-crashing). Such notification may be obtained through utrace.
-
-This tracing scheme plans to use a direct function call to tracing into buffers
-mapped in user-space. This should be an order of magnitude faster than the
-current Dtrace implementation (c.f.
-https://ltt.polymtl.ca/tracingwiki/index.php/DTrace) which uses a breakpoint to
-perform both dynamic and static user-space tracing. Performance comparison of
-a function call vs the int3 approach is available at
-http://sourceware.org/ml/systemtap/2006-q3/msg00793.html (see "Conclusion").
-
projects / lttv.git / commitdiff
