[PATCH v2 7/9] perf config: Add core.hybrid-merge to configure event merging

[Ian Rogers <irogers@google.com>]

Provide a core.hybrid-merge configuration option in .perfconfig
to allow enabling hybrid event aggregation by default, avoiding
the need to pass --hybrid-merge explicitly on every invocation.

The config value is a default rather than an explicit request, so with
--hierarchy it is ignored with a warning, while giving both
--hierarchy and --hybrid-merge on the command line remains an error.

perf stat has its own merging options for counting, the sampling
core.hybrid-merge deliberately doesn't alter it and its
--hybrid-merge must still be given explicitly.

Signed-off-by: Ian Rogers <irogers@google.com>
Assisted-by: Antigravity:gemini-3.1-pro
---
 tools/perf/Documentation/perf-config.txt |  8 ++++++++
 tools/perf/builtin-report.c              | 16 +++++++++++-----
 tools/perf/builtin-top.c                 | 22 +++++++++++++++-------
 tools/perf/util/config.c                 | 10 ++++++++++
 4 files changed, 44 insertions(+), 12 deletions(-)

diff --git a/tools/perf/Documentation/perf-config.txt b/tools/perf/Documentation/perf-config.txt
index 9b223f892829..73a320861dc1 100644
--- a/tools/perf/Documentation/perf-config.txt
+++ b/tools/perf/Documentation/perf-config.txt
@@ -217,6 +217,14 @@ core.*::
 		Sets a timeout (in milliseconds) for parsing 'addr2line'
 		output.  The default timeout is 5s.
 
+	hybrid-merge::
+		Merge matching events from all hybrid core PMUs into one display
+		by default. For example, if a wildcard expands to run on both p-cores and
+		e-cores, this aggregates them into a single view. This applies to
+		'perf report' and 'perf top', it is ignored with '--hierarchy' and
+		doesn't alter 'perf stat' where '--hybrid-merge' must be given
+		explicitly.
+
 tui.*, gtk.*::
 	Subcommands that can be configured here are 'top', 'report' and 'annotate'.
 	These values are booleans, for example:
diff --git a/tools/perf/builtin-report.c b/tools/perf/builtin-report.c
index bda4836fc524..30c6664507a5 100644
--- a/tools/perf/builtin-report.c
+++ b/tools/perf/builtin-report.c
@@ -1324,6 +1324,7 @@ int cmd_report(int argc, const char **argv)
 	int branch_mode = -1;
 	int last_key = 0;
 	bool branch_call_mode = false;
+	bool hybrid_merge_set = false;
 #define CALLCHAIN_DEFAULT_OPT  "graph,0.5,caller,function,percent"
 	static const char report_callchain_help[] = "Display call graph (stack chain/backtrace):\n\n"
 						    CALLCHAIN_REPORT_HELP
@@ -1460,8 +1461,8 @@ int cmd_report(int argc, const char **argv)
 		    parse_branch_mode),
 	OPT_BOOLEAN(0, "branch-history", &branch_call_mode,
 		    "add last branch records to call history"),
-	OPT_BOOLEAN(0, "hybrid-merge", &symbol_conf.hybrid_merge,
-		    "merge the same event across hybrid core PMUs"),
+	OPT_BOOLEAN_SET(0, "hybrid-merge", &symbol_conf.hybrid_merge, &hybrid_merge_set,
+			"merge the same event across hybrid core PMUs"),
 	OPT_STRING(0, "objdump", &objdump_path, "path",
 		   "objdump binary to use for disassembly and annotations"),
 	OPT_STRING(0, "addr2line", &addr2line_path, "path",
@@ -1562,9 +1563,14 @@ int cmd_report(int argc, const char **argv)
 	}
 
 	if (symbol_conf.report_hierarchy && symbol_conf.hybrid_merge) {
-		pr_err("Error: --hierarchy and --hybrid-merge are mutually exclusive.\n");
-		ret = -EINVAL;
-		goto exit;
+		if (hybrid_merge_set) {
+			pr_err("Error: --hierarchy and --hybrid-merge are mutually exclusive.\n");
+			ret = -EINVAL;
+			goto exit;
+		}
+		/* A config file default shouldn't fail an explicit option. */
+		pr_warning("core.hybrid-merge ignored: --hierarchy cannot display merged hybrid events\n");
+		symbol_conf.hybrid_merge = false;
 	}
 
 	if (disassembler_style) {
diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index 3bb3337f1244..02b76f6bd0bd 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -1314,9 +1314,11 @@ static int __cmd_top(struct perf_top *top)
 	}
 
 	/*
-	 * Use global stat_config that is zero meaning aggr_mode is AGGR_NONE
-	 * and hybrid_merge is false.
+	 * Use global stat_config that is zero meaning aggr_mode is AGGR_NONE.
+	 * Merging affects the event names as merged events share a name, all
+	 * other stat_config behavior is unwanted here.
 	 */
+	stat_config.hybrid_merge = symbol_conf.hybrid_merge;
 	evlist__uniquify_evsel_names(top->evlist, &stat_config);
 	ret = perf_top__start_counters(top);
 	if (ret)
@@ -1493,6 +1495,7 @@ int cmd_top(int argc, const char **argv)
 		.evlistp = &top.evlist,
 	};
 	bool branch_call_mode = false;
+	bool hybrid_merge_set = false;
 	struct record_opts *opts = &top.record_opts;
 	struct target *target = &opts->target;
 	const char *disassembler_style = NULL, *objdump_path = NULL, *addr2line_path = NULL;
@@ -1500,8 +1503,8 @@ int cmd_top(int argc, const char **argv)
 	OPT_CALLBACK('e', "event", &parse_events_option_args, "event",
 		     "event selector. use 'perf list' to list available events",
 		     parse_events_option),
-	OPT_BOOLEAN(0, "hybrid-merge", &symbol_conf.hybrid_merge,
-		    "merge the same event across hybrid core PMUs"),
+	OPT_BOOLEAN_SET(0, "hybrid-merge", &symbol_conf.hybrid_merge, &hybrid_merge_set,
+			"merge the same event across hybrid core PMUs"),
 	OPT_CALLBACK(0, "filter", &top.evlist, "filter",
 		     "event filter", parse_filter),
 	OPT_U64('c', "count", &opts->user_interval, "event period to sample"),
@@ -1691,9 +1694,14 @@ int cmd_top(int argc, const char **argv)
 		usage_with_options(top_usage, options);
 
 	if (symbol_conf.report_hierarchy && symbol_conf.hybrid_merge) {
-		pr_err("Error: --hierarchy and --hybrid-merge are mutually exclusive.\n");
-		status = -EINVAL;
-		goto out_put_evlist;
+		if (hybrid_merge_set) {
+			pr_err("Error: --hierarchy and --hybrid-merge are mutually exclusive.\n");
+			status = -EINVAL;
+			goto out_put_evlist;
+		}
+		/* A config file default shouldn't fail an explicit option. */
+		pr_warning("core.hybrid-merge ignored: --hierarchy cannot display merged hybrid events\n");
+		symbol_conf.hybrid_merge = false;
 	}
 
 	if (disassembler_style) {
diff --git a/tools/perf/util/config.c b/tools/perf/util/config.c
index b2972c35c1ec..8fe43b032e9a 100644
--- a/tools/perf/util/config.c
+++ b/tools/perf/util/config.c
@@ -470,6 +470,16 @@ static int perf_default_core_config(const char *var, const char *value)
 	if (!strcmp(var, "core.addr2line-disable-warn"))
 		symbol_conf.addr2line_disable_warn = perf_config_bool(var, value);
 
+	if (!strcmp(var, "core.hybrid-merge")) {
+		/*
+		 * Note, this is for sampling tools like perf report and top.
+		 * perf stat has its own merging options and the
+		 * stat_config.hybrid_merge of "perf stat --hybrid-merge" is
+		 * deliberately not set here.
+		 */
+		symbol_conf.hybrid_merge = perf_config_bool(var, value);
+	}
+
 	/* Add other config variables here. */
 	return 0;
 }
-- 
2.55.0.1032.g73a4cd73de-goog