perf trace: Bump --mmap-pages when --call-graph is used by the root user

To reduce the chances we'll overflow the mmap buffer, manual fine tuning
trumps this.

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-wxygbxmp1v9mng1ea28wet02@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/Documentation/perf-trace.txt b/tools/perf/Documentation/perf-trace.txt
index 146c6db21cbf1de4c9077866484bb4ad31a3fc1a..c075c002eaa407f7cb9cb8b41dff36a3c69757e2 100644 (file)
--- a/tools/perf/Documentation/perf-trace.txt
+++ b/tools/perf/Documentation/perf-trace.txt
@@ -123,6 +123,10 @@ 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'.
 
+        Using this will, for the root user, bump the value of --mmap-pages to 4
+        times the maximum for non-root users, based on the kernel.perf_event_mlock_kb
+        sysctl. This is done only if the user doesn't specify a --mmap-pages value.
+
 --kernel-syscall-graph::
         Show the kernel callchains on the syscall exit path.
 

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index 19f5100acc1d4ddb87e4814f6846300dafaf8033..026ec0c749b04f8dfbbf5a2e81c229a7abe85cf3 100644 (file)
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -3110,6 +3110,7 @@ int cmd_trace(int argc, const char **argv, const char *prefix __maybe_unused)
        OPT_END()
        };
        bool max_stack_user_set = true;
+       bool mmap_pages_user_set = true;
        const char * const trace_subcommands[] = { "record", NULL };
        int err;
        char bf[BUFSIZ];
@@ -3143,6 +3144,9 @@ int cmd_trace(int argc, const char **argv, const char *prefix __maybe_unused)
                trace.opts.sample_time = true;
        }
 
+       if (trace.opts.mmap_pages == UINT_MAX)
+               mmap_pages_user_set = false;
+
        if (trace.max_stack == UINT_MAX) {
                trace.max_stack = PERF_MAX_STACK_DEPTH;
                max_stack_user_set = false;
@@ -3153,8 +3157,12 @@ int cmd_trace(int argc, const char **argv, const char *prefix __maybe_unused)
                record_opts__parse_callchain(&trace.opts, &callchain_param, "dwarf", false);
 #endif
 
-       if (trace.opts.callgraph_set)
+       if (trace.opts.callgraph_set) {
+               if (!mmap_pages_user_set && geteuid() == 0)
+                       trace.opts.mmap_pages = perf_event_mlock_kb_in_pages() * 4;
+
                symbol_conf.use_callchain = true;
+       }
 
        if (trace.evlist->nr_entries > 0)
                evlist__set_evsel_handler(trace.evlist, trace__event_handler);