Hi,

Here are a few editorial comments for you...


On 1/10/20 8:07 AM, Masami Hiramatsu wrote:

Add a documentation about boot-time tracing options in
boot config.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 Documentation/admin-guide/bootconfig.rst |    2 
 Documentation/trace/boottime-trace.rst   |  184 ++++++++++++++++++++++++++++++
 Documentation/trace/index.rst            |    1 
 3 files changed, 187 insertions(+)
 create mode 100644 Documentation/trace/boottime-trace.rst

   prefix.

+with "kernel." prefix [2]_.
+
+.. [1] See :ref:`Documentation/admin-guide/bootconfig.rst <bootconfig>`
+.. [2] See :ref:`Documentation/admin-guide/kernel-parameters.rst <kernelparameters>`
+
+Ftrace Global Options
+---------------------
+
+Ftrace global options have "kernel." prefix in boot config, which means
+these options are passed as a part of kernel legacy command line.
+
+kernel.tp_printk
+   Output trace-event data on printk buffer too.
+
+kernel.dump_on_oops [= MODE]
+   Dump ftrace on Oops. If MODE = 1 or omitted, dump trace buffer
+   on all CPUs. If MODE = 2, dump a buffer on a CPU which kicks Oops.
+
+kernel.traceoff_on_warning
+   Stop tracing if WARN_ON() occurs.
+
+kernel.fgraph_max_depth = MAX_DEPTH
+   Set MAX_DEPTH to maximum depth of fgraph tracer.
+
+kernel.fgraph_filters = FILTER[, FILTER2...]
+   Add fgraph tracing function filters.
+
+kernel.fgraph_notraces = FILTER[, FILTER2...]
+   Add fgraph non tracing function filters.

                 non-tracing

+
+
+Ftrace Per-instance Options
+---------------------------
+
+These options can be used for each instance including global ftrace node.
+
+ftrace.[instance.INSTANCE.]options = OPT1[, OPT2[...]]
+   Enable given ftrace options.
+
+ftrace.[instance.INSTANCE.]trace_clock = CLOCK
+   Set given CLOCK to ftrace's trace_clock.
+
+ftrace.[instance.INSTANCE.]buffer_size = SIZE
+   Configure ftrace buffer size to SIZE. You can use "KB" or "MB"
+   for that SIZE.
+
+ftrace.[instance.INSTANCE.]alloc_snapshot
+   Allocate snapshot buffer.
+
+ftrace.[instance.INSTANCE.]cpumask = CPUMASK
+   Set CPUMASK as trace cpu-mask.
+
+ftrace.[instance.INSTANCE.]events = EVENT[, EVENT2[...]]
+   Enable given events on boot. You can use a wild card in EVENT.
+
+ftrace.[instance.INSTANCE.]tracer = TRACER
+   Set TRACER to current tracer on boot. (e.g. function)
+
+ftrace.[instance.INSTANCE.]ftrace.filters
+   This will take an array of tracing function filter rules

end with '.' as above descriptions.

+
+ftrace.[instance.INSTANCE.]ftrace.notraces
+   This will take an array of NON-tracing function filter rules

ditto

+
+
+Ftrace Per-Event Options
+------------------------
+
+These options are setting per-event options.
+
+ftrace.[instance.INSTANCE.]event.GROUP.EVENT.enable
+   Enables GROUP:EVENT tracing.

      Enable

+
+ftrace.[instance.INSTANCE.]event.GROUP.EVENT.filter = FILTER
+   Set FILTER rule to the GROUP:EVENT.
+
+ftrace.[instance.INSTANCE.]event.GROUP.EVENT.actions = ACTION[, ACTION2[...]]
+   Set ACTIONs to the GROUP:EVENT.
+
+ftrace.[instance.INSTANCE.]event.kprobes.EVENT.probes = PROBE[, PROBE2[...]]
+   Defines new kprobe event based on PROBEs. It is able to define
+   multiple probes on one event, but those must have same type of
+   arguments. This option is available only for the event which
+   group name is "kprobes".
+
+ftrace.[instance.INSTANCE.]event.synthetic.EVENT.fields = FIELD[, FIELD2[...]]
+   Defines new synthetic event with FIELDs. Each field should be
+   "type varname".
+
+Note that kprobe and synthetic event definitions can be written under
+instance node, but those are also visible from other instances. So please
+take care for event name conflict.
+
+
+Examples
+========
+
+For example, to add filter and actions for each event, define kprobe
+events, and synthetic events with histogram, write a boot config like
+below::
+
+  ftrace.event {
+        task.task_newtask {
+                filter = "pid < 128"
+                enable
+        }
+        kprobes.vfs_read {
+                probes = "vfs_read $arg1 $arg2"
+                filter = "common_pid < 200"
+                enable
+        }
+        synthetic.initcall_latency {
+                fields = "unsigned long func", "u64 lat"
+                actions = "hist:keys=func.sym,lat:vals=lat:sort=lat"
+        }
+        initcall.initcall_start {
+                actions = "hist:keys=func:ts0=common_timestamp.usecs"
+        }
+        initcall.initcall_finish {
+                actions = "hist:keys=func:lat=common_timestamp.usecs-$ts0:onmatch(initcall.initcall_start).initcall_latency(func,$lat)"
+        }
+  }
+
+Also, boottime tracing supports "instance" node, which allows us to run

         boot-time  [for consistency]

+several tracers for different purpose at once. For example, one tracer
+is for tracing functions start with "user\_", and others tracing "kernel\_"

                            starting

+functions, you can write boot config as below::
+
+  ftrace.instance {
+        foo {
+                tracer = "function"
+                ftrace.filters = "user_*"
+        }
+        bar {
+                tracer = "function"
+                ftrace.filters = "kernel_*"
+        }
+  }
+
+The instance node also accepts event nodes so that each instance
+can customize its event tracing.
+
+This boot-time tracing also supports ftrace kernel parameters via boot
+config.
+For example, following kernel parameters::
+
+ trace_options=sym-addr trace_event=initcall:* tp_printk trace_buf_size=1M ftrace=function ftrace_filter="vfs*"
+
+This can be written in boot config like below::
+
+  kernel {
+        trace_options = sym-addr
+        trace_event = "initcall:*"
+        tp_printk
+        trace_buf_size = 1M
+        ftrace = function
+        ftrace_filter = "vfs*"
+  }
+
+Note that parameters start with "kernel" prefix instead of "ftrace".

HTH.
-- 
~Randy