Re: [PATCH v8 08/18] perf ftrace: add support for tracing option 'func_stack_trace'
From: Arnaldo Carvalho de Melo
Date: Fri Aug 14 2020 - 08:24:45 EST
Em Sat, Aug 08, 2020 at 10:31:31AM +0800, Changbin Du escreveu:
> This adds support to display call trace for function tracer. To do this,
> just specify a '--func-opts call-graph' option.
Applied, thanks for providing the usage example and the output of the
tool, please consider making this more compact and similar to the other
perf tools as:
# perf ftrace -g -T vfs_read
# perf report -h -g
Usage: perf report [<options>]
-g, --call-graph <print_type,threshold[,print_limit],order,sort_key[,branch],value>
Display call graph (stack chain/backtrace):
print_type: call graph printing style (graph|flat|fractal|folded|none)
threshold: minimum call graph inclusion threshold (<percent>)
print_limit: maximum number of call graph entry (<number>)
order: call graph order (caller|callee)
sort_key: call graph sort key (function|address)
branch: include last branch info to call graph (branch)
value: call graph value (percent|period|count)
Default: graph,0.5,caller,function,percent
#
Is there a way to ask for a limit in the number of levels? That is
similar to /proc/sys/kernel/perf_event_max_stack (system wide) and
perf_event_attr.sample_max_stack (per event)?
One can ask for that per event:
# perf trace -e sched:*_wakeup/max-stack=2/ -e sched:*switch/max-stack=5/ --max-events=4
0.000 migration/0/12 sched:sched_switch(prev_comm: "migration/0", prev_pid: 12 (migration/0), prev_prio: 0, prev_state: 1, next_comm: "swapper/0", next_pid: 0, next_prio: 120)
__schedule ([kernel.kallsyms])
__schedule ([kernel.kallsyms])
schedule ([kernel.kallsyms])
smpboot_thread_fn ([kernel.kallsyms])
kthread ([kernel.kallsyms])
2.381 :0/0 sched:sched_wakeup(comm: "PacerThread", pid: 111637 (PacerThread), prio: 120, success: 1, target_cpu: 0)
ttwu_do_wakeup ([kernel.kallsyms])
ttwu_do_wakeup ([kernel.kallsyms])
2.387 :0/0 sched:sched_switch(prev_comm: "swapper/0", prev_pid: 0, prev_prio: 120, prev_state: 0, next_comm: "PacerThread", next_pid: 111637 (PacerThread), next_prio: 120)
__schedule ([kernel.kallsyms])
__schedule ([kernel.kallsyms])
schedule_idle ([kernel.kallsyms])
do_idle ([kernel.kallsyms])
cpu_startup_entry ([kernel.kallsyms])
2.410 PacerThread/111637 sched:sched_switch(prev_comm: "PacerThread", prev_pid: 111637 (PacerThread), prev_prio: 120, prev_state: 1, next_comm: "swapper/0", next_pid: 0, next_prio: 120)
__schedule ([kernel.kallsyms])
__schedule ([kernel.kallsyms])
schedule ([kernel.kallsyms])
futex_wait_queue_me ([kernel.kallsyms])
futex_wait ([kernel.kallsyms])
#
- Arnaldo
> $ sudo perf ftrace -T vfs_read --func-opts call-graph
> iio-sensor-prox-855 [003] 6168.369657: vfs_read <-ksys_read
> iio-sensor-prox-855 [003] 6168.369677: <stack trace>
> => vfs_read
> => ksys_read
> => __x64_sys_read
> => do_syscall_64
> => entry_SYSCALL_64_after_hwframe
> ...
>
> Signed-off-by: Changbin Du <changbin.du@xxxxxxxxx>
>
> ---
> v3: switch to uniform option --func-opts.
> v2: option name '-s' -> '--func-call-graph'
> ---
> tools/perf/Documentation/perf-ftrace.txt | 4 +++
> tools/perf/builtin-ftrace.c | 42 ++++++++++++++++++++++++
> 2 files changed, 46 insertions(+)
>
> diff --git a/tools/perf/Documentation/perf-ftrace.txt b/tools/perf/Documentation/perf-ftrace.txt
> index c46d0a09b38c..8f08ad0992c2 100644
> --- a/tools/perf/Documentation/perf-ftrace.txt
> +++ b/tools/perf/Documentation/perf-ftrace.txt
> @@ -76,6 +76,10 @@ OPTIONS
> specify multiple functions (or glob patterns). It will be
> passed to 'set_ftrace_notrace' in tracefs.
>
> +--func-opts::
> + List of options allowed to set:
> + call-graph - Display kernel stack trace for function tracer.
> +
> -G::
> --graph-funcs=::
> Select function_graph tracer and set graph filter on the given
> diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
> index 07b81d0c1658..469b89748c42 100644
> --- a/tools/perf/builtin-ftrace.c
> +++ b/tools/perf/builtin-ftrace.c
> @@ -27,6 +27,7 @@
> #include "util/cap.h"
> #include "util/config.h"
> #include "util/units.h"
> +#include "util/parse-sublevel-options.h"
>
> #define DEFAULT_TRACER "function_graph"
>
> @@ -42,6 +43,7 @@ struct perf_ftrace {
> int graph_depth;
> unsigned long percpu_buffer_size;
> bool inherit;
> + int func_stack_trace;
> };
>
> struct filter_entry {
> @@ -202,6 +204,7 @@ static void reset_tracing_filters(void);
> static void reset_tracing_options(struct perf_ftrace *ftrace __maybe_unused)
> {
> write_tracing_option_file("function-fork", "0");
> + write_tracing_option_file("func_stack_trace", "0");
> }
>
> static int reset_tracing_files(struct perf_ftrace *ftrace __maybe_unused)
> @@ -278,6 +281,17 @@ static int set_tracing_cpu(struct perf_ftrace *ftrace)
> return set_tracing_cpumask(cpumap);
> }
>
> +static int set_tracing_func_stack_trace(struct perf_ftrace *ftrace)
> +{
> + if (!ftrace->func_stack_trace)
> + return 0;
> +
> + if (write_tracing_option_file("func_stack_trace", "1") < 0)
> + return -1;
> +
> + return 0;
> +}
> +
> static int reset_tracing_cpu(void)
> {
> struct perf_cpu_map *cpumap = perf_cpu_map__new(NULL);
> @@ -426,6 +440,11 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace, int argc, const char **argv)
> goto out_reset;
> }
>
> + if (set_tracing_func_stack_trace(ftrace) < 0) {
> + pr_err("failed to set tracing option func_stack_trace\n");
> + goto out_reset;
> + }
> +
> if (set_tracing_filters(ftrace) < 0) {
> pr_err("failed to set tracing filters\n");
> goto out_reset;
> @@ -598,6 +617,26 @@ static int parse_buffer_size(const struct option *opt,
> return -1;
> }
>
> +static int parse_func_tracer_opts(const struct option *opt,
> + const char *str, int unset)
> +{
> + int ret;
> + struct perf_ftrace *ftrace = (struct perf_ftrace *) opt->value;
> + struct sublevel_option func_tracer_opts[] = {
> + { .name = "call-graph", .value_ptr = &ftrace->func_stack_trace },
> + { .name = NULL, }
> + };
> +
> + if (unset)
> + return 0;
> +
> + ret = perf_parse_sublevel_options(str, func_tracer_opts);
> + if (ret)
> + return ret;
> +
> + return 0;
> +}
> +
> static void select_tracer(struct perf_ftrace *ftrace)
> {
> bool graph = !list_empty(&ftrace->graph_funcs) ||
> @@ -645,6 +684,9 @@ int cmd_ftrace(int argc, const char **argv)
> parse_filter_func),
> OPT_CALLBACK('N', "notrace-funcs", &ftrace.notrace, "func",
> "do not trace given functions", parse_filter_func),
> + OPT_CALLBACK(0, "func-opts", &ftrace, "options",
> + "function tracer options, available options: call-graph",
> + parse_func_tracer_opts),
> OPT_CALLBACK('G', "graph-funcs", &ftrace.graph_funcs, "func",
> "trace given functions using function_graph tracer",
> parse_filter_func),
> --
> 2.25.1
>
--
- Arnaldo