perf report/top: Add option to collapse undesired parts of call graph

For example, in an application with an expensive function implemented
with deeply nested recursive calls, the default call-graph presentation
is dominated by the different callchains within that function.  By
ignoring these callees, we can collect the callchains leading into the
function and compactly identify what to blame for expensive calls.

For example, in this report the callers of garbage_collect() are
scattered across the tree:

  $ perf report -d ruby 2>- | grep -m10 ^[^#]*[a-z]
      22.03%     ruby  [.] gc_mark
                 --- gc_mark
                    |--59.40%-- mark_keyvalue
                    |          st_foreach
                    |          gc_mark_children
                    |          |--99.75%-- rb_gc_mark
                    |          |          rb_vm_mark
                    |          |          gc_mark_children
                    |          |          gc_marks
                    |          |          |--99.00%-- garbage_collect

If we ignore the callees of garbage_collect(), its callers are coalesced:

  $ perf report --ignore-callees garbage_collect -d ruby 2>- | grep -m10 ^[^#]*[a-z]
      72.92%     ruby  [.] garbage_collect
                 --- garbage_collect
                     vm_xmalloc
                    |--47.08%-- ruby_xmalloc
                    |          st_insert2
                    |          rb_hash_aset
                    |          |--98.45%-- features_index_add
                    |          |          rb_provide_feature
                    |          |          rb_require_safe
                    |          |          vm_call_method
Signed-off-by: Greg Price <price@mit.edu>
Tested-by: Jiri Olsa <jolsa@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20130623031720.GW22203@biohazard-cafe.mit.edu
Link: http://lkml.kernel.org/r/20130708115746.GO22203@biohazard-cafe.mit.edu
Cc: Fengguang Wu <fengguang.wu@intel.com>
[ remove spaces at beginning of line, reported by Fengguang Wu ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/Documentation/perf-report.txt

@@ -135,6 +135,11 @@ OPTIONS
 --inverted::
         alias for inverted caller based call graph.
 
+--ignore-callees=<regex>::
+        Ignore callees of the function(s) matching the given regex.
+        This has the effect of collecting the callers of each such
+        function into one place in the call-graph tree.
+
 --pretty=<key>::
         Pretty printing style.  key: normal, raw
 

tools/perf/Documentation/perf-top.txt

@@ -155,6 +155,11 @@ Default is to monitor all CPUS.
 
 	Default: fractal,0.5,callee.
 
+--ignore-callees=<regex>::
+        Ignore callees of the function(s) matching the given regex.
+        This has the effect of collecting the callers of each such
+        function into one place in the call-graph tree.
+
 --percent-limit::
 	Do not show entries which have an overhead under that percent.
 	(Default: 0).

tools/perf/builtin-report.c

@@ -89,7 +89,7 @@ static int perf_report__add_mem_hist_entry(struct perf_tool *tool,
 	if ((sort__has_parent || symbol_conf.use_callchain) &&
 	    sample->callchain) {
 		err = machine__resolve_callchain(machine, evsel, al->thread,
-						 sample, &parent);
+						 sample, &parent, al);
 		if (err)
 			return err;
 	}
@@ -180,7 +180,7 @@ static int perf_report__add_branch_hist_entry(struct perf_tool *tool,
 	if ((sort__has_parent || symbol_conf.use_callchain)
 	    && sample->callchain) {
 		err = machine__resolve_callchain(machine, evsel, al->thread,
-						 sample, &parent);
+						 sample, &parent, al);
 		if (err)
 			return err;
 	}
@@ -254,7 +254,7 @@ static int perf_evsel__add_hist_entry(struct perf_evsel *evsel,
 
 	if ((sort__has_parent || symbol_conf.use_callchain) && sample->callchain) {
 		err = machine__resolve_callchain(machine, evsel, al->thread,
-						 sample, &parent);
+						 sample, &parent, al);
 		if (err)
 			return err;
 	}
@@ -681,6 +681,24 @@ parse_callchain_opt(const struct option *opt, const char *arg, int unset)
 	return 0;
 }
 
+int
+report_parse_ignore_callees_opt(const struct option *opt __maybe_unused,
+				const char *arg, int unset __maybe_unused)
+{
+	if (arg) {
+		int err = regcomp(&ignore_callees_regex, arg, REG_EXTENDED);
+		if (err) {
+			char buf[BUFSIZ];
+			regerror(err, &ignore_callees_regex, buf, sizeof(buf));
+			pr_err("Invalid --ignore-callees regex: %s\n%s", arg, buf);
+			return -1;
+		}
+		have_ignore_callees = 1;
+	}
+
+	return 0;
+}
+
 static int
 parse_branch_mode(const struct option *opt __maybe_unused,
 		  const char *str __maybe_unused, int unset)
@@ -771,6 +789,9 @@ int cmd_report(int argc, const char **argv, const char *prefix __maybe_unused)
 		     "Default: fractal,0.5,callee", &parse_callchain_opt, callchain_default_opt),
 	OPT_BOOLEAN('G', "inverted", &report.inverted_callchain,
 		    "alias for inverted call graph"),
+	OPT_CALLBACK(0, "ignore-callees", NULL, "regex",
+		   "ignore callees of these functions in call graphs",
+		   report_parse_ignore_callees_opt),
 	OPT_STRING('d', "dsos", &symbol_conf.dso_list_str, "dso[,dso...]",
 		   "only consider symbols in these dsos"),
 	OPT_STRING('c', "comms", &symbol_conf.comm_list_str, "comm[,comm...]",

tools/perf/builtin-top.c

@@ -773,8 +773,7 @@ static void perf_event__process_sample(struct perf_tool *tool,
 		    sample->callchain) {
 			err = machine__resolve_callchain(machine, evsel,
 							 al.thread, sample,
-							 &parent);
-
+							 &parent, &al);
 			if (err)
 				return;
 		}
@@ -1109,6 +1108,9 @@ int cmd_top(int argc, const char **argv, const char *prefix __maybe_unused)
 	OPT_CALLBACK_DEFAULT('G', "call-graph", &top.record_opts,
 			     "mode[,dump_size]", record_callchain_help,
 			     &parse_callchain_opt, "fp"),
+	OPT_CALLBACK(0, "ignore-callees", NULL, "regex",
+		   "ignore callees of these functions in call graphs",
+		   report_parse_ignore_callees_opt),
 	OPT_BOOLEAN(0, "show-total-period", &symbol_conf.show_total_period,
 		    "Show a column with the sum of periods"),
 	OPT_STRING(0, "dsos", &symbol_conf.dso_list_str, "dso[,dso...]",

tools/perf/util/machine.c

@@ -1058,11 +1058,10 @@ int machine__process_event(struct machine *machine, union perf_event *event)
 	return ret;
 }
 
-static bool symbol__match_parent_regex(struct symbol *sym)
+static bool symbol__match_regex(struct symbol *sym, regex_t *regex)
 {
-	if (sym->name && !regexec(&parent_regex, sym->name, 0, NULL, 0))
+	if (sym->name && !regexec(regex, sym->name, 0, NULL, 0))
 		return 1;
-
 	return 0;
 }
 
@@ -1159,8 +1158,8 @@ struct branch_info *machine__resolve_bstack(struct machine *machine,
 static int machine__resolve_callchain_sample(struct machine *machine,
 					     struct thread *thread,
 					     struct ip_callchain *chain,
-					     struct symbol **parent)
-
+					     struct symbol **parent,
+					     struct addr_location *root_al)
 {
 	u8 cpumode = PERF_RECORD_MISC_USER;
 	unsigned int i;
@@ -1211,8 +1210,15 @@ static int machine__resolve_callchain_sample(struct machine *machine,
 					   MAP__FUNCTION, ip, &al, NULL);
 		if (al.sym != NULL) {
 			if (sort__has_parent && !*parent &&
-			    symbol__match_parent_regex(al.sym))
+			    symbol__match_regex(al.sym, &parent_regex))
 				*parent = al.sym;
+			else if (have_ignore_callees && root_al &&
+			  symbol__match_regex(al.sym, &ignore_callees_regex)) {
+				/* Treat this symbol as the root,
+				   forgetting its callees. */
+				*root_al = al;
+				callchain_cursor_reset(&callchain_cursor);
+			}
 			if (!symbol_conf.use_callchain)
 				break;
 		}
@@ -1237,13 +1243,13 @@ int machine__resolve_callchain(struct machine *machine,
 			       struct perf_evsel *evsel,
 			       struct thread *thread,
 			       struct perf_sample *sample,
-			       struct symbol **parent)
-
+			       struct symbol **parent,
+			       struct addr_location *root_al)
 {
 	int ret;
 
 	ret = machine__resolve_callchain_sample(machine, thread,
-						sample->callchain, parent);
+						sample->callchain, parent, root_al);
 	if (ret)
 		return ret;
 

tools/perf/util/machine.h

@@ -5,6 +5,7 @@
 #include <linux/rbtree.h>
 #include "map.h"
 
+struct addr_location;
 struct branch_stack;
 struct perf_evsel;
 struct perf_sample;
@@ -83,7 +84,8 @@ int machine__resolve_callchain(struct machine *machine,
 			       struct perf_evsel *evsel,
 			       struct thread *thread,
 			       struct perf_sample *sample,
-			       struct symbol **parent);
+			       struct symbol **parent,
+			       struct addr_location *root_al);
 
 /*
  * Default guest kernel is defined by parameter --guestkallsyms

tools/perf/util/session.c

@@ -1406,9 +1406,8 @@ void perf_evsel__print_ip(struct perf_evsel *evsel, union perf_event *event,
 
 	if (symbol_conf.use_callchain && sample->callchain) {
 
-
 		if (machine__resolve_callchain(machine, evsel, al.thread,
-					       sample, NULL) != 0) {
+					       sample, NULL, NULL) != 0) {
 			if (verbose)
 				error("Failed to resolve callchain. Skipping\n");
 			return;

tools/perf/util/sort.c

@@ -7,6 +7,8 @@ const char	default_parent_pattern[] = "^sys_|^do_page_fault";
 const char	*parent_pattern = default_parent_pattern;
 const char	default_sort_order[] = "comm,dso,symbol";
 const char	*sort_order = default_sort_order;
+regex_t		ignore_callees_regex;
+int		have_ignore_callees = 0;
 int		sort__need_collapse = 0;
 int		sort__has_parent = 0;
 int		sort__has_sym = 0;

tools/perf/util/sort.h

@@ -29,6 +29,8 @@ extern const char *sort_order;
 extern const char default_parent_pattern[];
 extern const char *parent_pattern;
 extern const char default_sort_order[];
+extern regex_t ignore_callees_regex;
+extern int have_ignore_callees;
 extern int sort__need_collapse;
 extern int sort__has_parent;
 extern int sort__has_sym;
@@ -183,4 +185,6 @@ int setup_sorting(void);
 extern int sort_dimension__add(const char *);
 void sort__setup_elide(FILE *fp);
 
+int report_parse_ignore_callees_opt(const struct option *opt, const char *arg, int unset);
+
 #endif	/* __PERF_SORT_H */