Re: [PATCH] perf tool: add skip_not_exec_file_map_events option

[Ian Rogers]

On Wed, Aug 17, 2022 at 6:43 AM tcwzxx <tcwzxx@xxxxxxxxx> wrote:
>
> When generate the flame graph, the perf-script subcommand will
> process all mmap event and add them to the rbtree. The 240,000
> mmap region takes about 5 minutes, which is not useful for flame
> graph. So add the skip-not-exec-file-map-events option to skip
> not PROT_EXEC flag memory regions.
>
> Signed-off-by: tcwzxx <tcwzxx@xxxxxxxxx>

Could you provide more context? A reproduction?

When we synthesize mmap events we drop non-executable pages:
https://github.com/torvalds/linux/blob/master/tools/perf/util/synthetic-events.c#L466

Similarly in the kernel for the "dummy" event:
https://github.com/torvalds/linux/blob/master/kernel/events/core.c#L8258

Thanks,
Ian

> ---
>  tools/perf/builtin-report.c | 2 ++
>  tools/perf/builtin-script.c | 3 +++
>  tools/perf/util/machine.c   | 3 +++
>  tools/perf/util/map.c       | 5 +++++
>  tools/perf/util/map.h       | 2 ++
>  5 files changed, 15 insertions(+)
>
> diff --git a/tools/perf/builtin-report.c b/tools/perf/builtin-report.c
> index 91ed41cc7d88..c28eb9450a66 100644
> --- a/tools/perf/builtin-report.c
> +++ b/tools/perf/builtin-report.c
> @@ -1364,6 +1364,8 @@ int cmd_report(int argc, const char **argv)
>                     "Disable raw trace ordering"),
>         OPT_BOOLEAN(0, "skip-empty", &report.skip_empty,
>                     "Do not display empty (or dummy) events in the output"),
> +       OPT_BOOLEAN(0, "skip-not-exec-file-map_events", &skip_not_exec_file_map_events,
> +                   "skip not exec map events"),
>         OPT_END()
>         };
>         struct perf_data data = {
> diff --git a/tools/perf/builtin-script.c b/tools/perf/builtin-script.c
> index 13580a9c50b8..e3f4e5e654c9 100644
> --- a/tools/perf/builtin-script.c
> +++ b/tools/perf/builtin-script.c
> @@ -32,6 +32,7 @@
>  #include "util/time-utils.h"
>  #include "util/path.h"
>  #include "util/event.h"
> +#include "util/map.h"
>  #include "ui/ui.h"
>  #include "print_binary.h"
>  #include "archinsn.h"
> @@ -3936,6 +3937,8 @@ int cmd_script(int argc, const char **argv)
>                     "Guest code can be found in hypervisor process"),
>         OPT_BOOLEAN('\0', "stitch-lbr", &script.stitch_lbr,
>                     "Enable LBR callgraph stitching approach"),
> +       OPT_BOOLEAN(0, "skip-not-exec-map_events", &skip_not_exec_file_map_events,
> +                   "skip not exec map events"),
>         OPTS_EVSWITCH(&script.evswitch),
>         OPT_END()
>         };
> diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
> index 2a16cae28407..21dde9f9935c 100644
> --- a/tools/perf/util/machine.c
> +++ b/tools/perf/util/machine.c
> @@ -1904,6 +1904,9 @@ int machine__process_mmap2_event(struct machine *machine,
>         if (thread == NULL)
>                 goto out_problem;
>
> +       if (skip_not_exec_file_map_events && !(event->mmap2.prot & PROT_EXEC))
> +               goto out_problem;
> +
>         map = map__new(machine, event->mmap2.start,
>                         event->mmap2.len, event->mmap2.pgoff,
>                         &dso_id, event->mmap2.prot,
> diff --git a/tools/perf/util/map.c b/tools/perf/util/map.c
> index e0aa4a254583..2b51ca012c91 100644
> --- a/tools/perf/util/map.c
> +++ b/tools/perf/util/map.c
> @@ -16,6 +16,8 @@
>  #include "thread.h"
>  #include "vdso.h"
>
> +bool skip_not_exec_file_map_events;
> +
>  static inline int is_android_lib(const char *filename)
>  {
>         return strstarts(filename, "/data/app-lib/") ||
> @@ -168,6 +170,9 @@ struct map *map__new(struct machine *machine, u64 start, u64 len,
>                 if (dso == NULL)
>                         goto out_delete;
>
> +               if (skip_not_exec_file_map_events && dso__type(dso, machine) == DSO__TYPE_UNKNOWN)
> +                       goto out_delete;
> +
>                 map__init(map, start, start + len, pgoff, dso);
>
>                 if (anon || no_dso) {
> diff --git a/tools/perf/util/map.h b/tools/perf/util/map.h
> index 3dcfe06db6b3..67b0e0f9f0ae 100644
> --- a/tools/perf/util/map.h
> +++ b/tools/perf/util/map.h
> @@ -11,6 +11,8 @@
>  #include <stdbool.h>
>  #include <linux/types.h>
>
> +extern bool skip_not_exec_file_map_events;
> +
>  struct dso;
>  struct maps;
>  struct machine;
> --
> 2.34.1
>