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Date: Thu, 6 Aug 2020 08:14:48 +0800
From: Changbin Du <changbin.du@...il.com>
To: Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
Cc: Changbin Du <changbin.du@...il.com>, Jiri Olsa <jolsa@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
Namhyung Kim <namhyung@...nel.org>,
Steven Rostedt <rostedt@...dmis.org>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 01/18] perf ftrace: select function/function_graph
tracer automatically
On Tue, Aug 04, 2020 at 09:51:15AM -0300, Arnaldo Carvalho de Melo wrote:
> Em Sat, Jul 18, 2020 at 02:48:09PM +0800, Changbin Du escreveu:
> > The '-g/-G' options have already implied function_graph tracer should be
> > used instead of function tracer. So the extra option '--tracer' can be
> > killed.
> >
> > This patch changes the behavior as below:
> > - By default, function tracer is used.
> > - If '-g' or '-G' option is on, then function_graph tracer is used.
> > - The perf configuration item 'ftrace.tracer' is marked as deprecated.
> > - The option '--tracer' is marked as deprecated.
>
> You should try to be more granular, for instance, I think the decision
> to change the default is questionable, but could be acceptable.
>
> But why deprecate the perf configuration for the default tracer?
>
> Say people who already use 'perf ftrace ls' go and use with this patch
> and see that it changed the default from the function_graph tracer to
> the function tracer and disagree with you, they want the default to be
> the function graph tracer, know that there is (or there was) a
> ftrace.tracer in ~/.prefconfig, and then try that, only to find out that
> it is not possible, frustrating :-\
>
> So can we please remove this deprecation of ftrace.tracer so that people
> used to how it was can get that behaviour back?
>
Agreed. If no -F or -G is given, we can use the ftrace.tracer as default tracer.
Let me update it. Thanks.
> I'll look at the other patches so as to provide comments on all of
> them and to speed things up I may end up removing this deprecation of
> ftrace.tracer and apply the rest, we can always revisit parts that I
> remove.
>
> - Arnaldo
>
> > Here are some examples.
> >
> > This will start tracing all functions using function tracer:
> > $ sudo perf ftrace
> >
> > This will trace all functions using function graph tracer:
> > $ sudo perf ftrace -G '*'
> >
> > This will trace function vfs_read using function graph tracer:
> > $ sudo perf ftrace -G vfs_read
> >
> > Signed-off-by: Changbin Du <changbin.du@...il.com>
> >
> > ---
> > v3: remove default '*' for -G/-T.
> > ---
> > tools/perf/Documentation/perf-config.txt | 5 -----
> > tools/perf/Documentation/perf-ftrace.txt | 2 +-
> > tools/perf/builtin-ftrace.c | 15 ++++++++++-----
> > 3 files changed, 11 insertions(+), 11 deletions(-)
> >
> > diff --git a/tools/perf/Documentation/perf-config.txt b/tools/perf/Documentation/perf-config.txt
> > index c7d3df5798e2..a25fee7de3b2 100644
> > --- a/tools/perf/Documentation/perf-config.txt
> > +++ b/tools/perf/Documentation/perf-config.txt
> > @@ -612,11 +612,6 @@ trace.*::
> > "libbeauty", the default, to use the same argument beautifiers used in the
> > strace-like sys_enter+sys_exit lines.
> >
> > -ftrace.*::
> > - ftrace.tracer::
> > - Can be used to select the default tracer. Possible values are
> > - 'function' and 'function_graph'.
> > -
> > llvm.*::
> > llvm.clang-path::
> > Path to clang. If omit, search it from $PATH.
> > diff --git a/tools/perf/Documentation/perf-ftrace.txt b/tools/perf/Documentation/perf-ftrace.txt
> > index b80c84307dc9..952e46669168 100644
> > --- a/tools/perf/Documentation/perf-ftrace.txt
> > +++ b/tools/perf/Documentation/perf-ftrace.txt
> > @@ -24,7 +24,7 @@ OPTIONS
> >
> > -t::
> > --tracer=::
> > - Tracer to use: function_graph or function.
> > + Tracer to use: function_graph or function. This option is deprecated.
> >
> > -v::
> > --verbose=::
> > diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
> > index 2bfc1b0db536..5f53da87040d 100644
> > --- a/tools/perf/builtin-ftrace.c
> > +++ b/tools/perf/builtin-ftrace.c
> > @@ -27,7 +27,6 @@
> > #include "util/cap.h"
> > #include "util/config.h"
> >
> > -#define DEFAULT_TRACER "function_graph"
> >
> > struct perf_ftrace {
> > struct evlist *evlist;
> > @@ -419,6 +418,7 @@ static int perf_ftrace_config(const char *var, const char *value, void *cb)
> > if (strcmp(var, "ftrace.tracer"))
> > return -1;
> >
> > + pr_warning("Configuration ftrace.tracer is deprecated\n");
> > if (!strcmp(value, "function_graph") ||
> > !strcmp(value, "function")) {
> > ftrace->tracer = value;
> > @@ -459,7 +459,7 @@ int cmd_ftrace(int argc, const char **argv)
> > {
> > int ret;
> > struct perf_ftrace ftrace = {
> > - .tracer = DEFAULT_TRACER,
> > + .tracer = "function",
> > .target = { .uid = UINT_MAX, },
> > };
> > const char * const ftrace_usage[] = {
> > @@ -469,7 +469,7 @@ int cmd_ftrace(int argc, const char **argv)
> > };
> > const struct option ftrace_options[] = {
> > OPT_STRING('t', "tracer", &ftrace.tracer, "tracer",
> > - "tracer to use: function_graph(default) or function"),
> > + "tracer to use: function or function_graph (This option is deprecated)"),
> > OPT_STRING('p', "pid", &ftrace.target.pid, "pid",
> > "trace on existing process id"),
> > OPT_INCR('v', "verbose", &verbose,
> > @@ -479,11 +479,13 @@ int cmd_ftrace(int argc, const char **argv)
> > OPT_STRING('C', "cpu", &ftrace.target.cpu_list, "cpu",
> > "list of cpus to monitor"),
> > OPT_CALLBACK('T', "trace-funcs", &ftrace.filters, "func",
> > - "trace given functions only", parse_filter_func),
> > + "trace given functions using function tracer",
> > + parse_filter_func),
> > OPT_CALLBACK('N', "notrace-funcs", &ftrace.notrace, "func",
> > "do not trace given functions", parse_filter_func),
> > OPT_CALLBACK('G', "graph-funcs", &ftrace.graph_funcs, "func",
> > - "Set graph filter on given functions", parse_filter_func),
> > + "trace given functions using function_graph tracer",
> > + parse_filter_func),
> > OPT_CALLBACK('g', "nograph-funcs", &ftrace.nograph_funcs, "func",
> > "Set nograph filter on given functions", parse_filter_func),
> > OPT_INTEGER('D', "graph-depth", &ftrace.graph_depth,
> > @@ -505,6 +507,9 @@ int cmd_ftrace(int argc, const char **argv)
> > if (!argc && target__none(&ftrace.target))
> > ftrace.target.system_wide = true;
> >
> > + if (!list_empty(&ftrace.graph_funcs) || !list_empty(&ftrace.nograph_funcs))
> > + ftrace.tracer = "function_graph";
> > +
> > ret = target__validate(&ftrace.target);
> > if (ret) {
> > char errbuf[512];
> > --
> > 2.25.1
> >
>
> --
>
> - Arnaldo
--
Cheers,
Changbin Du
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