From: Bagas Sanjaya Date: Tue, 16 Sep 2025 05:41:59 +0000 (+0700) Subject: Documentation: trace: histogram: Fix histogram trigger subsection number order X-Git-Tag: v6.18-rc1~107^2~8 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=348b7ca8d3f7fdc7bc28ef219253cb31c218fdb0;p=thirdparty%2Fkernel%2Fstable.git Documentation: trace: histogram: Fix histogram trigger subsection number order Section numbering in subsections of "Histogram Trigger Command" sections is inconsistent in order. In particular, "'hist' trigger examples" is erroneously numbered as 6.2, which is a leftover from b8df4a3634e08a ("tracing: Move hist trigger Documentation to histogram.txt"). Fix the order. Reviewed-by: Tom Zanussi Reviewed-by: Masami Hiramatsu (Google) Signed-off-by: Bagas Sanjaya Acked-by: Steven Rostedt (Google) Signed-off-by: Jonathan Corbet Message-ID: <20250916054202.582074-3-bagasdotme@gmail.com> --- diff --git a/Documentation/trace/histogram.rst b/Documentation/trace/histogram.rst index af6d2e15568eb..d158dadaa4244 100644 --- a/Documentation/trace/histogram.rst +++ b/Documentation/trace/histogram.rst @@ -186,8 +186,8 @@ Documentation written by Tom Zanussi The examples below provide a more concrete illustration of the concepts and typical usage patterns discussed above. -'special' event fields ------------------------- +2.1. 'special' event fields +--------------------------- There are a number of 'special event fields' available for use as keys or values in a hist trigger. These look like and behave as if @@ -204,16 +204,16 @@ Documentation written by Tom Zanussi common_cpu int the cpu on which the event occurred. ====================== ==== ======================================= -Extended error information --------------------------- +2.2. Extended error information +------------------------------- For some error conditions encountered when invoking a hist trigger command, extended error information is available via the tracing/error_log file. See Error Conditions in :file:`Documentation/trace/ftrace.rst` for details. -6.2 'hist' trigger examples ---------------------------- +2.3. 'hist' trigger examples +---------------------------- The first set of examples creates aggregations using the kmalloc event. The fields that can be used for the hist trigger are listed @@ -1608,8 +1608,8 @@ Extended error information Entries: 7 Dropped: 0 -2.2 Inter-event hist triggers ------------------------------ +2.4. Inter-event hist triggers +------------------------------ Inter-event hist triggers are hist triggers that combine values from one or more other events and create a histogram using that data. Data @@ -1685,8 +1685,8 @@ pseudo-file. These features are described in more detail in the following sections. -2.2.1 Histogram Variables -------------------------- +2.5. Histogram Variables +------------------------ Variables are simply named locations used for saving and retrieving values between matching events. A 'matching' event is defined as an @@ -1789,8 +1789,8 @@ or assigned to a variable and referenced in a subsequent expression:: Variables can even hold stacktraces, which are useful with synthetic events. -2.2.2 Synthetic Events ----------------------- +2.6. Synthetic Events +--------------------- Synthetic events are user-defined events generated from hist trigger variables or fields associated with one or more other events. Their @@ -1846,7 +1846,7 @@ the command that defined it with a '!':: At this point, there isn't yet an actual 'wakeup_latency' event instantiated in the event subsystem - for this to happen, a 'hist trigger action' needs to be instantiated and bound to actual fields -and variables defined on other events (see Section 2.2.3 below on +and variables defined on other events (see Section 2.7. below on how that is done using hist trigger 'onmatch' action). Once that is done, the 'wakeup_latency' synthetic event instance is created. @@ -2094,8 +2094,8 @@ histogram:: Entries: 7 Dropped: 0 -2.2.3 Hist trigger 'handlers' and 'actions' -------------------------------------------- +2.7. Hist trigger 'handlers' and 'actions' +------------------------------------------ A hist trigger 'action' is a function that's executed (in most cases conditionally) whenever a histogram entry is added or updated. @@ -2526,8 +2526,8 @@ The following commonly-used handler.action pairs are available: kworker/3:2-135 [003] d..3 49.823123: sched_switch: prev_comm=kworker/3:2 prev_pid=135 prev_prio=120 prev_state=T ==> next_comm=swapper/3 next_pid=0 next_prio=120 -0 [004] ..s7 49.823798: tcp_probe: src=10.0.0.10:54326 dest=23.215.104.193:80 mark=0x0 length=32 snd_nxt=0xe3ae2ff5 snd_una=0xe3ae2ecd snd_cwnd=10 ssthresh=2147483647 snd_wnd=28960 srtt=19604 rcv_wnd=29312 -3. User space creating a trigger --------------------------------- +2.8. User space creating a trigger +---------------------------------- Writing into /sys/kernel/tracing/trace_marker writes into the ftrace ring buffer. This can also act like an event, by writing into the trigger