perf trace: Exclude the kernel part of the callchain leading to a syscall

The kernel parts are not that useful:

  # trace -m 512 -e nanosleep --call dwarf  usleep 1
     0.065 ( 0.065 ms): usleep/18732 nanosleep(rqtp: 0x7ffc4ee4e200) = 0
                                       syscall_slow_exit_work ([kernel.kallsyms])
                                       do_syscall_64 ([kernel.kallsyms])
                                       return_from_SYSCALL_64 ([kernel.kallsyms])
                                       __nanosleep (/usr/lib64/libc-2.22.so)
                                       usleep (/usr/lib64/libc-2.22.so)
                                       main (/usr/bin/usleep)
                                       __libc_start_main (/usr/lib64/libc-2.22.so)
                                       _start (/usr/bin/usleep)
  #

So lets just use perf_event_attr.exclude_callchain_kernel to avoid
collecting it in the ring buffer:

  # trace -m 512 -e nanosleep --call dwarf  usleep 1
     0.063 ( 0.063 ms): usleep/19212 nanosleep(rqtp: 0x7ffc3df10fb0) = 0
                                       __nanosleep (/usr/lib64/libc-2.22.so)
                                       usleep (/usr/lib64/libc-2.22.so)
                                       main (/usr/bin/usleep)
                                       __libc_start_main (/usr/lib64/libc-2.22.so)
                                       _start (/usr/bin/usleep)
  #

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Milian Wolff <milian.wolff@kdab.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-qctu3gqhpim0dfbcp9d86c91@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

2 files changed, 16 insertions, 0 deletions

diff --git a/tools/perf/Documentation/perf-trace.txt b/tools/perf/Documentation/perf-trace.txt
index ed485df16409..1bbcf305d233 100644
--- a/tools/perf/Documentation/perf-trace.txt
+++ b/tools/perf/Documentation/perf-trace.txt
@@ -123,6 +123,9 @@ the thread executes on the designated CPUs. Default is to monitor all CPUs.
         man pages for details. The ones that are most useful in 'perf trace'
         are 'dwarf' and 'lbr', where available, try: 'perf trace --call-graph dwarf'.
 
+--kernel-syscall-graph::
+         Show the kernel callchains on the syscall exit path.
+
 --event::
         Trace other events, see 'perf list' for a complete list.
 
diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index 63a3cc9b717c..cfa5ce8fdb7b 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -159,6 +159,7 @@ struct trace {
         bool                    show_comm;
         bool                    show_tool_stats;
         bool                    trace_syscalls;
+        bool                    kernel_syscallchains;
         bool                    force;
         bool                    vfs_getname;
         int                     trace_pgfaults;
@@ -2661,6 +2662,15 @@ static int trace__add_syscall_newtp(struct trace *trace)
         perf_evlist__add(evlist, sys_enter);
         perf_evlist__add(evlist, sys_exit);
 
+        if (trace->opts.callgraph_set && !trace->kernel_syscallchains) {
+                /*
+                 * We're interested only in the user space callchain
+                 * leading to the syscall, allow overriding that for
+                 * debugging reasons using --kernel_syscall_callchains
+                 */
+                sys_exit->attr.exclude_callchain_kernel = 1;
+        }
+
         trace->syscalls.events.sys_enter = sys_enter;
         trace->syscalls.events.sys_exit  = sys_exit;
 
@@ -3221,6 +3231,7 @@ int cmd_trace(int argc, const char **argv, const char *prefix __maybe_unused)
                 .output = stderr,
                 .show_comm = true,
                 .trace_syscalls = true,
+                .kernel_syscallchains = false,
         };
         const char *output_name = NULL;
         const char *ev_qualifier_str = NULL;
@@ -3269,6 +3280,8 @@ int cmd_trace(int argc, const char **argv, const char *prefix __maybe_unused)
         OPT_CALLBACK(0, "call-graph", &trace.opts,
                      "record_mode[,record_size]", record_callchain_help,
                      &record_parse_callchain_opt),
+        OPT_BOOLEAN(0, "kernel-syscall-graph", &trace.kernel_syscallchains,
+                    "Show the kernel callchains on the syscall exit path"),
         OPT_UINTEGER(0, "proc-map-timeout", &trace.opts.proc_map_timeout,
                         "per thread proc mmap processing timeout in ms"),
         OPT_END()