Implement malloc_info(3).

Expose jemalloc stats through the malloc_info(3) interface.

Bug: 16874689
Change-Id: I4358ac283002e60ff161107028d1a3fb1e9afb0a

libc/bionic/malloc_info.cpp

@@ -0,0 +1,94 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "malloc_info.h"
+
+#include <errno.h>
+#include "private/bionic_macros.h"
+
+class __LIBC_HIDDEN__ Elem {
+public:
+  // name must be valid throughout lifetime of the object.
+  explicit Elem(FILE* fp, const char* name,
+                const char* attr_fmt = nullptr, ...) {
+    this->fp = fp;
+    this->name = name;
+
+    fprintf(fp, "<%s", name);
+    if (attr_fmt != nullptr) {
+      va_list args;
+      va_start(args, attr_fmt);
+      fputc(' ', fp);
+      vfprintf(fp, attr_fmt, args);
+      va_end(args);
+    }
+    fputc('>', fp);
+  }
+
+  ~Elem() noexcept {
+    fprintf(fp, "</%s>", name);
+  }
+
+  void contents(const char* fmt, ...) {
+      va_list args;
+      va_start(args, fmt);
+      vfprintf(fp, fmt, args);
+      va_end(args);
+  }
+
+private:
+  FILE* fp;
+  const char* name;
+
+  DISALLOW_COPY_AND_ASSIGN(Elem);
+};
+
+int malloc_info(int options, FILE* fp) {
+  if (options != 0) {
+    errno = EINVAL;
+    return -1;
+  }
+
+  Elem root(fp, "malloc", "version=\"jemalloc-1\"");
+
+  // Dump all of the large allocations in the arenas.
+  for (size_t i = 0; i < __mallinfo_narenas(); i++) {
+    struct mallinfo mi = __mallinfo_arena_info(i);
+    if (mi.hblkhd != 0) {
+      Elem arena_elem(fp, "heap", "nr=\"%d\"", i);
+      {
+        Elem(fp, "allocated-large").contents("%zu", mi.ordblks);
+        Elem(fp, "allocated-huge").contents("%zu", mi.uordblks);
+        Elem(fp, "allocated-bins").contents("%zu", mi.fsmblks);
+
+        size_t total = 0;
+        for (size_t j = 0; j < __mallinfo_nbins(); j++) {
+          struct mallinfo mi = __mallinfo_bin_info(i, j);
+          if (mi.ordblks != 0) {
+            Elem bin_elem(fp, "bin", "nr=\"%d\"", j);
+            Elem(fp, "allocated").contents("%zu", mi.ordblks);
+            Elem(fp, "nmalloc").contents("%zu", mi.uordblks);
+            Elem(fp, "ndalloc").contents("%zu", mi.fordblks);
+            total += mi.ordblks;
+          }
+        }
+        Elem(fp, "bins-total").contents("%zu", total);
+      }
+    }
+  }
+
+  return 0;
+}