diff options
Diffstat (limited to 'doc/HACKING/Tracing.md')
| -rw-r--r-- | doc/HACKING/Tracing.md | 22 |
1 files changed, 16 insertions, 6 deletions
diff --git a/doc/HACKING/Tracing.md b/doc/HACKING/Tracing.md index d898bee172..0f2196c3f8 100644 --- a/doc/HACKING/Tracing.md +++ b/doc/HACKING/Tracing.md @@ -28,7 +28,7 @@ Tracing is separated in two different concepts. The tracing API and the tracing probes. The API is in `src/lib/trace/` which defines how to call tracepoints in the -tor code. Every C files should include `src/lib/trace/events.h" if they want +tor code. Every C files should include `src/lib/trace/events.h` if they want to call a tracepoint. The probes are what actually record the tracepoint data. Because they often @@ -43,7 +43,9 @@ subsystem and an event name. A trace event in tor has the following standard format: - tor_trace(subsystem, event\_name, args...) +```c +tor_trace(subsystem, event\_name, args...); +``` The `subsystem` parameter is the name of the subsytem the trace event is in. For example that could be "scheduler" or "vote" or "hs". The idea is to add @@ -57,7 +59,9 @@ The `args` can be any number of arguments we want to collect. Here is an example of a possible tracepoint in main(): - tor_trace(main, init_phase, argc) +```c +tor_trace(main, init_phase, argc); +``` The above is a tracepoint in the `main` subsystem with `init\_phase` as the event name and the `int argc` is passed to the event as one argument. @@ -80,7 +84,9 @@ Currently, we have 3 types of possible instrumentation: arguments will be passed on because we don't know their type nor the string format of the debug log. The output is standardized like this: - [debug] __FUNC__: Tracepoint <event_name> from subsystem <subsystem> hit. +``` +[debug] __FUNC__: Tracepoint <event_name> from subsystem <subsystem> hit. +``` 2. USDT @@ -125,12 +131,16 @@ They can all be used together or independently. If one of them is set, This is pretty easy. Let's say you want to add a trace event in `src/feature/rend/rendcache.c`, you first need to include this file: - #include "lib/trace/events.h" +```c +#include "trace/events.h" +``` Then, the `tor\_trace()` macro can be used with the specific format detailled before in a previous section. As an example: - tor_trace(hs, store_desc_as_client, desc, desc_id); +```c +tor_trace(hs, store_desc_as_client, desc, desc_id); +``` For `Debug` instrumentation, you have nothing else to do. |