perf hist: Support multi-line header

This is a preparation to support multi-line headers in 'perf mem report'.

Normal sort keys and output fields that don't have contents for multi-
line will print the header string at the last line only.

As we don't use multi-line headers normally, it should not have any
changes in the output.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Leo Yan <leo.yan@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Link: https://lore.kernel.org/r/20250430205548.789750-4-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 35 insertions, 22 deletions

diff --git a/tools/perf/ui/stdio/hist.c b/tools/perf/ui/stdio/hist.c
index 7ac4b98e28bc..8c4c8925df2c 100644
--- a/tools/perf/ui/stdio/hist.c
+++ b/tools/perf/ui/stdio/hist.c
@@ -643,45 +643,58 @@ static int hists__fprintf_hierarchy_headers(struct hists *hists,
 	unsigned header_width = 0;
 	struct perf_hpp_fmt *fmt;
 	struct perf_hpp_list_node *fmt_node;
+	struct perf_hpp_list *hpp_list = hists->hpp_list;
 	const char *sep = symbol_conf.field_sep;
 
 	indent = hists->nr_hpp_node;
 
-	/* preserve max indent depth for column headers */
-	print_hierarchy_indent(sep, indent, " ", fp);
-
 	/* the first hpp_list_node is for overhead columns */
 	fmt_node = list_first_entry(&hists->hpp_formats,
 				    struct perf_hpp_list_node, list);
 
-	perf_hpp_list__for_each_format(&fmt_node->hpp, fmt) {
-		fmt->header(fmt, hpp, hists, 0, NULL);
-		fprintf(fp, "%s%s", hpp->buf, sep ?: "  ");
-	}
+	for (int line = 0; line < hpp_list->nr_header_lines; line++) {
+		/* first # is displayed one level up */
+		if (line)
+			fprintf(fp, "# ");
 
-	/* combine sort headers with ' / ' */
-	first_node = true;
-	list_for_each_entry_continue(fmt_node, &hists->hpp_formats, list) {
-		if (!first_node)
-			header_width += fprintf(fp, " / ");
-		first_node = false;
+		/* preserve max indent depth for column headers */
+		print_hierarchy_indent(sep, indent, " ", fp);
 
-		first_col = true;
 		perf_hpp_list__for_each_format(&fmt_node->hpp, fmt) {
-			if (perf_hpp__should_skip(fmt, hists))
-				continue;
+			fmt->header(fmt, hpp, hists, line, NULL);
+			fprintf(fp, "%s%s", hpp->buf, sep ?: "  ");
+		}
 
-			if (!first_col)
-				header_width += fprintf(fp, "+");
-			first_col = false;
+		if (line < hpp_list->nr_header_lines - 1)
+			goto next_line;
+
+		/* combine sort headers with ' / ' */
+		first_node = true;
+		list_for_each_entry_continue(fmt_node, &hists->hpp_formats, list) {
+			if (!first_node)
+				header_width += fprintf(fp, " / ");
+			first_node = false;
 
-			fmt->header(fmt, hpp, hists, 0, NULL);
+			first_col = true;
+			perf_hpp_list__for_each_format(&fmt_node->hpp, fmt) {
+				if (perf_hpp__should_skip(fmt, hists))
+					continue;
 
-			header_width += fprintf(fp, "%s", strim(hpp->buf));
+				if (!first_col)
+					header_width += fprintf(fp, "+");
+				first_col = false;
+
+				fmt->header(fmt, hpp, hists, line, NULL);
+
+				header_width += fprintf(fp, "%s", strim(hpp->buf));
+			}
 		}
+
+next_line:
+		fprintf(fp, "\n");
 	}
 
-	fprintf(fp, "\n# ");
+	fprintf(fp, "# ");
 
 	/* preserve max indent depth for initial dots */
 	print_hierarchy_indent(sep, indent, dots, fp);