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SubjectRe: [PATCH v3 00/14] tracing: Add triggers to trace_marker writes
Hi Steve,

On Wed, May 16, 2018 at 11:00:12AM -0400, Steven Rostedt wrote:
> A few people have asked for this in the past, and I finally got around
> to implementing it. What this does is to allow writes into trace_marker
> to initiate a trigger.
>
> The trace_marker event is described in:
>
> tracefs/events/ftrace/print
>
> Thus the trigger file is added there:
>
> tracefs/events/ftrace/print/trigger
>
> As there's already a "hist" file there, everything appears to work
> just like any other trigger to an event. See the last patch for
> documentation on how to use the triggers to a trace_marker write.
>
> By the way, the patch:
>
> tracing: Prevent further users of zero size static arrays in trace events
>
> May prevent your kernel from building if you include Xen. You will need
> to add this patch to make it work (or include the git repo below).
>
> http://lkml.kernel.org/r/20180509144605.5a220327@gandalf.local.home
>
>
> git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git
> ftrace/core
>
> Head SHA1: dded7b759602085b4bd2c5581f58f6b179912d89
>
>
> Steven Rostedt (VMware) (14):
> tracing: Do not reference event data in post call triggers
> tracing: Add __find_event_file() to find event files without restrictions
> tracing: Have event_trace_init() called by trace_init_tracefs()
> tracing: Add brackets in ftrace event dynamic arrays
> tracing: Do not show filter file for ftrace internal events
> tracing: Add trigger file for trace_markers tracefs/ftrace/print
> tracing: Have zero size length in filter logic be full string
> tracing: Prevent further users of zero size static arrays in trace events
> tracing: Allow histogram triggers to access ftrace internal events
> tracing: Document trace_marker triggers
> ftrace/selftest: Have the reset_trigger code be a bit more careful
> ftrace/selftest: Fix reset_trigger() to handle triggers with filters
> tracing/selftest: Add selftests to test trace_marker histogram triggers
> tracing/selftest: Add test to test hist trigger between kernel event and trace_marker
>
> ----

For the series:

Reviewed-by: Namhyung Kim <namhyung@kernel.org>

Thanks,
Namhyung


> Changes since v2:
>
> - typo fixes in documentation (Tom Zanussi)
> - Rename trigger-trace-marker{-hist} in selftest (Masami Hiramatsu)
> - Fix onmatch(sched.sched_waking) (Namhyung Kim)
> - Rename test to say trace_marker trigger from event trigger (Steven Rostedt)
>
> Diff from v2 below.
>
> Documentation/trace/events.rst | 6 +-
> Documentation/trace/ftrace.rst | 5 +
> Documentation/trace/histogram.txt | 546 ++++++++++++++++++++-
> include/linux/trace_events.h | 3 +-
> include/trace/trace_events.h | 1 +
> kernel/trace/trace.c | 19 +
> kernel/trace/trace.h | 9 +-
> kernel/trace/trace_entries.h | 6 +-
> kernel/trace/trace_events.c | 36 +-
> kernel/trace/trace_events_filter.c | 23 +-
> kernel/trace/trace_events_hist.c | 2 +-
> kernel/trace/trace_events_trigger.c | 6 +-
> kernel/trace/trace_export.c | 9 +-
> tools/testing/selftests/ftrace/test.d/functions | 23 +-
> .../test.d/trigger/trigger-trace-marker-hist.tc | 49 ++
> .../trigger/trigger-trace-marker-synthetic.tc | 88 ++++
> 16 files changed, 790 insertions(+), 41 deletions(-)
> create mode 100644 tools/testing/selftests/ftrace/test.d/trigger/trigger-trace-marker-hist.tc
> create mode 100644 tools/testing/selftests/ftrace/test.d/trigger/trigger-trace-marker-synthetic.tc
>
>
> diff --git a/Documentation/trace/histogram.txt b/Documentation/trace/histogram.txt
> index 8c871f0c0e33..ae2d4f9d0a62 100644
> --- a/Documentation/trace/histogram.txt
> +++ b/Documentation/trace/histogram.txt
> @@ -2005,7 +2005,7 @@ and after it wakes up, something like this:
>
> static void traceputs(char *str)
> {
> - /* tracemark_fd is the trace_marker file descripto */
> + /* tracemark_fd is the trace_marker file descriptor */
> if (tracemark_fd < 0)
> return;
> /* write the tracemark message */
> @@ -2048,7 +2048,7 @@ Now running cyclictest with:
>
> Note, the -b 1000 is used just to make --tracemark available.
>
> -The we can see the histogram created by this with:
> +Then we can see the histogram created by this with:
>
> # cat events/synthetic/latency/hist
> # event histogram
> @@ -2360,7 +2360,7 @@ kernel with trace_marker.
>
> The difference this time is that instead of using the trace_marker to start
> the latency, the sched_waking event is used, matching the common_pid for the
> -trace_marker write with the pid that is being worken by sched_waking.
> +trace_marker write with the pid that is being woken by sched_waking.
>
> After running cyclictest again with the same parameters, we now have:
>
> @@ -2535,5 +2535,5 @@ Totals:
> Dropped: 0
>
> This doesn't tell us any information about how late cyclictest may have
> -worken up, but it does show us a nice histogram of how long it took from
> -the time that cyclictest was worken to the time it made it into user space.
> +woken up, but it does show us a nice histogram of how long it took from
> +the time that cyclictest was woken to the time it made it into user space.
> diff --git a/tools/testing/selftests/ftrace/test.d/trigger/trigger-trace-marker.tc b/tools/testing/selftests/ftrace/test.d/trigger/trigger-trace-marker-hist.tc
> similarity index 93%
> rename from tools/testing/selftests/ftrace/test.d/trigger/trigger-trace-marker.tc
> rename to tools/testing/selftests/ftrace/test.d/trigger/trigger-trace-marker-hist.tc
> index 48e7ac1ccbc1..2acbfe2c0c0c 100644
> --- a/tools/testing/selftests/ftrace/test.d/trigger/trigger-trace-marker.tc
> +++ b/tools/testing/selftests/ftrace/test.d/trigger/trigger-trace-marker-hist.tc
> @@ -1,6 +1,6 @@
> #!/bin/sh
> # SPDX-License-Identifier: GPL-2.0
> -# description: event trigger - test histogram trigger
> +# description: trace_marker trigger - test histogram trigger
> # flags: instance
>
> do_reset() {
> diff --git a/tools/testing/selftests/ftrace/test.d/trigger/trigger-trace-marker-synthetic.tc b/tools/testing/selftests/ftrace/test.d/trigger/trigger-trace-marker-synthetic.tc
> index d8cfc36f228b..b06996ecd5e0 100644
> --- a/tools/testing/selftests/ftrace/test.d/trigger/trigger-trace-marker-synthetic.tc
> +++ b/tools/testing/selftests/ftrace/test.d/trigger/trigger-trace-marker-synthetic.tc
> @@ -1,6 +1,6 @@
> #!/bin/sh
> # SPDX-License-Identifier: GPL-2.0
> -# description: event trigger - test histogram with synthetic event
> +# description: trace_marker trigger - test histogram with synthetic event
> # flags:
>
> do_reset() {
> @@ -72,7 +72,7 @@ echo "Test histogram kernel event to trace_marker latency histogram trigger"
>
> echo 'latency u64 lat' > synthetic_events
> echo 'hist:keys=pid:ts0=common_timestamp.usecs' > events/sched/sched_waking/trigger
> -echo 'hist:keys=common_pid:lat=common_timestamp.usecs-$ts0:onmatch(ftrace.print).latency($lat)' > events/ftrace/print/trigger
> +echo 'hist:keys=common_pid:lat=common_timestamp.usecs-$ts0:onmatch(sched.sched_waking).latency($lat)' > events/ftrace/print/trigger
> echo 'hist:keys=common_pid,lat:sort=lat' > events/synthetic/latency/trigger
> sleep 1
> echo "hello" > trace_marker

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