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    SubjectRe: [PATCH 03/19] perf ftrace: select function/function_graph tracer automatically
    Em Sun, May 10, 2020 at 11:06:12PM +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.

    Well, since it is there, lets not remove it, you can even add a
    "Deprecated" message to it and then after some time, remove it.

    Also, in this area, -g is used for asking for callchains in other perf
    tools, so its a candidate for a change in behaviour, as well with some
    deprecation warning for a while, using --call-graph for a while, etc.

    I.e. we want it to have a similar set of options as the other perf
    tools, so that switching from, say:

    # perf trace <options> workload

    To:

    # perf ftrace <options> workload

    Would provide a similar experience, only that the first is limited to
    syscalls, the other to kernel functions.

    - Arnaldo


    > 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 removed.
    > - The default filter for -G is to trace all functions.
    >
    > 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@gmail.com>
    > ---
    > tools/perf/Documentation/perf-config.txt | 5 ---
    > tools/perf/builtin-ftrace.c | 39 ++++++------------------
    > 2 files changed, 9 insertions(+), 35 deletions(-)
    >
    > diff --git a/tools/perf/Documentation/perf-config.txt b/tools/perf/Documentation/perf-config.txt
    > index f16d8a71d3f5..fad6c48ed76a 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/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
    > index 5584f8dec25d..57e656c35d28 100644
    > --- a/tools/perf/builtin-ftrace.c
    > +++ b/tools/perf/builtin-ftrace.c
    > @@ -27,7 +27,7 @@
    > #include "util/cap.h"
    > #include "util/config.h"
    >
    > -#define DEFAULT_TRACER "function_graph"
    > +#define DEFAULT_TRACER "function"
    >
    > struct perf_ftrace {
    > struct evlist *evlist;
    > @@ -408,26 +408,6 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace, int argc, const char **argv)
    > return (done && !workload_exec_errno) ? 0 : -1;
    > }
    >
    > -static int perf_ftrace_config(const char *var, const char *value, void *cb)
    > -{
    > - struct perf_ftrace *ftrace = cb;
    > -
    > - if (!strstarts(var, "ftrace."))
    > - return 0;
    > -
    > - if (strcmp(var, "ftrace.tracer"))
    > - return -1;
    > -
    > - if (!strcmp(value, "function_graph") ||
    > - !strcmp(value, "function")) {
    > - ftrace->tracer = value;
    > - return 0;
    > - }
    > -
    > - pr_err("Please select \"function_graph\" (default) or \"function\"\n");
    > - return -1;
    > -}
    > -
    > static int parse_filter_func(const struct option *opt, const char *str,
    > int unset __maybe_unused)
    > {
    > @@ -467,8 +447,6 @@ int cmd_ftrace(int argc, const char **argv)
    > NULL
    > };
    > const struct option ftrace_options[] = {
    > - OPT_STRING('t', "tracer", &ftrace.tracer, "tracer",
    > - "tracer to use: function_graph(default) or function"),
    > OPT_STRING('p', "pid", &ftrace.target.pid, "pid",
    > "trace on existing process id"),
    > OPT_INCR('v', "verbose", &verbose,
    > @@ -481,10 +459,12 @@ int cmd_ftrace(int argc, const char **argv)
    > "trace given functions only", 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),
    > + OPT_CALLBACK_DEFAULT('G', "graph-funcs", &ftrace.graph_funcs, "func",
    > + "Set graph filter on given functions (imply to use function_graph tracer)",
    > + parse_filter_func, "*"),
    > OPT_CALLBACK('g', "nograph-funcs", &ftrace.nograph_funcs, "func",
    > - "Set nograph filter on given functions", parse_filter_func),
    > + "Set nograph filter on given functions (imply to use function_graph tracer)",
    > + parse_filter_func),
    > OPT_INTEGER('D', "graph-depth", &ftrace.graph_depth,
    > "Max depth for function graph tracer"),
    > OPT_END()
    > @@ -495,15 +475,14 @@ int cmd_ftrace(int argc, const char **argv)
    > INIT_LIST_HEAD(&ftrace.graph_funcs);
    > INIT_LIST_HEAD(&ftrace.nograph_funcs);
    >
    > - ret = perf_config(perf_ftrace_config, &ftrace);
    > - if (ret < 0)
    > - return -1;
    > -
    > argc = parse_options(argc, argv, ftrace_options, ftrace_usage,
    > PARSE_OPT_STOP_AT_NON_OPTION);
    > 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

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