Messages in this thread | | | From | zhizhi xu <> | Date | Fri, 19 Aug 2022 11:18:55 +0800 | Subject | Re: [PATCH] perf tool: add skip_not_exec_file_map_events option |
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On Thu, 18 Aug 2022 at 23:00, Ian Rogers <irogers@google.com> wrote: > > On Wed, Aug 17, 2022 at 8:24 PM lika you <tcwzxx@gmail.com> wrote: > > > > I'm so sorry for forgetting to reply to all. Here is the reply again. > > > > Thanks for the reply. > > > > The background is we have two types of tasks running on the same host.The high > > priority one which is CPU overhead and the low priority which is IO overhead. > > The high priority task has mmap many files as shared memory. The low priority > > task may load multi TB data from SSD at once time which will cause the high > > priority task file page cache to be swapped out. So we mmap all files with the > > PROT_EXEC flag to prevent hot page cache to be swapped out. That cause > > too many executable memory regions without symbols on it. > > > > The trick is implementate here. > > https://github.com/torvalds/linux/blob/master/mm/vmscan.c#L2572 > > > > Thanks again > > Thanks. So you are making data pages executable for the sake of > getting "better chances to stay in memory under moderate memory > pressure." Having lots of executable pages in your program isn't > great, I'm reminded of efforts to stop stacks from being executable. > This also feels like a case where madvise should be being used, for > example, the MADV_WILLNEED option. Given this, I'm not sure supporting > this case in the perf tool makes sense. > > > On Thu, 18 Aug 2022 at 02:13, Ian Rogers <irogers@google.com> wrote: > > > > > > On Wed, Aug 17, 2022 at 6:43 AM tcwzxx <tcwzxx@gmail.com> 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@gmail.com> > > > > > > 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; > > Do you mean to drop all executable pages with the flag here or just > those with the DSO__TYPE_UNKNOWN (as below)? It reads that all > executable pages will be dropped. > > Thanks, > Ian >
Thank you for your advice. I mean remove non-executable pages and non-ELF files
!(event->mmap2.prot & PROT_EXEC)
Thanks
> > > > + > > > > 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 > > > >
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