Documentation: tracing: Add histogram syntax to boot-time tracing
Add the documentation about histogram syntax in boot-time tracing. This will allow user to write the histogram setting in a structured parameters. Link: https://lkml.kernel.org/r/162856127129.203126.15551542847575916525.stgit@devnote2 Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
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Masami Hiramatsu
Steven Rostedt (VMware)
parent
64dc7f6958
commit
5597895392
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@ -125,6 +125,71 @@ Note that kprobe and synthetic event definitions can be written under
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instance node, but those are also visible from other instances. So please
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take care for event name conflict.
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Ftrace Histogram Options
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------------------------
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Since it is too long to write a histogram action as a string for per-event
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action option, there are tree-style options under per-event 'hist' subkey
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for the histogram actions. For the detail of the each parameter,
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please read the event histogram document [3]_.
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.. [3] See :ref:`Documentation/trace/histogram.rst <histogram>`
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ftrace.[instance.INSTANCE.]event.GROUP.EVENT.hist.[N.]keys = KEY1[, KEY2[...]]
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Set histogram key parameters. (Mandatory)
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The 'N' is a digit string for the multiple histogram. You can omit it
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if there is one histogram on the event.
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ftrace.[instance.INSTANCE.]event.GROUP.EVENT.hist.[N.]values = VAL1[, VAL2[...]]
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Set histogram value parameters.
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ftrace.[instance.INSTANCE.]event.GROUP.EVENT.hist.[N.]sort = SORT1[, SORT2[...]]
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Set histogram sort parameter options.
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ftrace.[instance.INSTANCE.]event.GROUP.EVENT.hist.[N.]size = NR_ENTRIES
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Set histogram size (number of entries).
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ftrace.[instance.INSTANCE.]event.GROUP.EVENT.hist.[N.]name = NAME
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Set histogram name.
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ftrace.[instance.INSTANCE.]event.GROUP.EVENT.hist.[N.]var.VARIABLE = EXPR
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Define a new VARIABLE by EXPR expression.
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ftrace.[instance.INSTANCE.]event.GROUP.EVENT.hist.[N.]<pause|continue|clear>
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Set histogram control parameter. You can set one of them.
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ftrace.[instance.INSTANCE.]event.GROUP.EVENT.hist.[N.]onmatch.[M.]event = GROUP.EVENT
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Set histogram 'onmatch' handler matching event parameter.
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The 'M' is a digit string for the multiple 'onmatch' handler. You can omit it
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if there is one 'onmatch' handler on this histogram.
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ftrace.[instance.INSTANCE.]event.GROUP.EVENT.hist.[N.]onmatch.[M.]trace = EVENT[, ARG1[...]]
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Set histogram 'trace' action for 'onmatch'.
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EVENT must be a synthetic event name, and ARG1... are parameters
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for that event. Mandatory if 'onmatch.event' option is set.
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ftrace.[instance.INSTANCE.]event.GROUP.EVENT.hist.[N.]onmax.[M.]var = VAR
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Set histogram 'onmax' handler variable parameter.
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ftrace.[instance.INSTANCE.]event.GROUP.EVENT.hist.[N.]onchange.[M.]var = VAR
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Set histogram 'onchange' handler variable parameter.
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ftrace.[instance.INSTANCE.]event.GROUP.EVENT.hist.[N.]<onmax|onchange>.[M.]save = ARG1[, ARG2[...]]
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Set histogram 'save' action parameters for 'onmax' or 'onchange' handler.
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This option or below 'snapshot' option is mandatory if 'onmax.var' or
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'onchange.var' option is set.
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ftrace.[instance.INSTANCE.]event.GROUP.EVENT.hist.[N.]<onmax|onchange>.[M.]snapshot
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Set histogram 'snapshot' action for 'onmax' or 'onchange' handler.
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This option or above 'save' option is mandatory if 'onmax.var' or
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'onchange.var' option is set.
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ftrace.[instance.INSTANCE.]event.GROUP.EVENT.hist.filter = FILTER_EXPR
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Set histogram filter expression. You don't need 'if' in the FILTER_EXPR.
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Note that this 'hist' option can conflict with the per-event 'actions'
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option if the 'actions' option has a histogram action.
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When to Start
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=============
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@ -159,13 +224,23 @@ below::
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}
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synthetic.initcall_latency {
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fields = "unsigned long func", "u64 lat"
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actions = "hist:keys=func.sym,lat:vals=lat:sort=lat"
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hist {
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keys = func.sym, lat
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values = lat
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sort = lat
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}
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}
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initcall.initcall_start {
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actions = "hist:keys=func:ts0=common_timestamp.usecs"
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initcall.initcall_start.hist {
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keys = func
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var.ts0 = common_timestamp.usecs
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}
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initcall.initcall_finish {
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actions = "hist:keys=func:lat=common_timestamp.usecs-$ts0:onmatch(initcall.initcall_start).initcall_latency(func,$lat)"
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initcall.initcall_finish.hist {
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keys = func
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var.lat = common_timestamp.usecs - $ts0
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onmatch {
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event = initcall.initcall_start
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trace = initcall_latency, func, $lat
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}
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}
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}
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