Merge 'perf_tests: Right-align numeric metrics in markdown tables' fr…

…om Kefu Chai

Right-align metrics columns in markdown output for better number comparison. Previously, metrics were left-aligned in markdown tables but right-aligned in stdout, making it difficult to visually compare numbers.

The change adds colons to the right of hyphens in the header row (e.g. `|---:|`) to right-align entire columns. While this affects both headers and data cells, the improved readability of numeric values outweighs the minor tradeoff of right-aligned headers.

In short:
- Uses `column::print_text` with ":>" alignment for consistent formatting
- Maintains existing stdout_printer right alignment
- Updates `markdown_printer` alignment to match stdout behavior

Closes #2619

* https://github.com/scylladb/seastar:
  perf_tests: Inline print_text_header() into stdout_printer
  perf_tests: Right-align numeric metrics in markdown tables

tests/perf/perf_tests.cc

@@ -258,23 +258,6 @@ struct column {
 
 using columns = std::vector<column>;
 
-static void print_text_header(std::FILE* out,
-    const columns& cols,
-    int name_length,
-    const char* start_delim = "",   // before the line
-    const char* middle_delim = " ", // between each column
-    const char* end_delim = "",     // end of line
-    const char* test_name_header = "test",
-    const char* header_override = nullptr) {
-
-    fmt::print(out, "{}{:<{}}", start_delim, header_override ? header_override : test_name_header, name_length);
-    for (auto& c : cols) {
-        fmt::print(out, "{}", middle_delim);
-        c.print_header(out, header_override);
-    }
-    fmt::print(out, "{}\n", end_delim);
-}
-
 static void print_result_columns(std::FILE* out,
     const columns& cols,
     int name_length,
@@ -321,7 +304,15 @@ struct stdout_printer final : result_printer {
                "number of runs:", c.number_of_runs,
                "number of cores:", smp::count,
                "random seed:", c.random_seed);
-    print_text_header(stdout, text_columns, name_column_length());
+
+    fmt::print("{:<{}}", "test", name_column_length());
+    for (auto& c : text_columns) {
+        // a middle delimiter between each column
+        fmt::print(" ");
+        c.print_header(stdout);
+    }
+    // end of line
+    fmt::print("\n");
   }
 
   virtual void print_result(const result& r) override {
@@ -357,6 +348,21 @@ class json_printer final : public result_printer {
 
 class markdown_printer final : public result_printer {
     std::FILE* _output = nullptr;
+
+    void print_header_row(const char* head_text, const char* body_text) {
+        // start delimeter, and the top-left cell
+        fmt::print(_output, "| {:<{}}", head_text, name_column_length());
+        // the header cells
+        for (auto& c : text_columns) {
+            // middle delimeter
+            fmt::print(_output, " | ");
+            // right align the text in result cells
+            c.print_header(_output, body_text);
+        }
+        // end delimeter
+        fmt::print(_output, " |\n");
+    }
+
 public:
     explicit markdown_printer(const std::string& filename) {
         if (filename == "-") {
@@ -375,9 +381,10 @@ class markdown_printer final : public result_printer {
     }
 
     void print_configuration(const config&) override {
-        // print the header row, then the divider row of all -
-        print_text_header(_output, text_columns, name_column_length(), "| ", " | ", " |", "test");
-        print_text_header(_output, text_columns, name_column_length(), "| ", " | ", " |", "test", "-");
+        // print the header row
+        print_header_row("test", nullptr);
+        // then the divider row of all -
+        print_header_row("-", "-:");
     }
 
     void print_result(const result& r) override {