Memory statistics split into Effective and Overhead

This feature is intended mostly for checking that BIRD's allocation
strategies don't consume much memory space. There are some cases where
withdrawing routes in a specific order lead to memory fragmentation and
this output should give the user at least a notion of how much memory is
actually used for data storage and how much memory is "just allocated"
or used for overhead.

Also raising the "system allocator overhead estimation" from 8 to 16
bytes; it is probably even more. I've found 16 as a local minimum in
best scenarios among reachable machines. I couldn't find any reasonable
method to estimate this value when BIRD starts up.

This commit also fixes the inaccurate computation of memory overhead for
slabs where the "system allocater overhead estimation" was improperly
added to the size of mmap-ed memory.

1 files changed, 35 insertions, 9 deletions

diff --git a/nest/cmds.c b/nest/cmds.c
index f58923a7..1a16f9c7 100644
--- a/nest/cmds.c
+++ b/nest/cmds.c
@@ -67,18 +67,43 @@ cmd_show_symbols(struct sym_show_data *sd)
   }
 }
 
-static void
-print_size(char *dsc, size_t val)
+#define SIZE_SUFFIX	" kMGT"
+#define SIZE_FORMAT	"% 4u.%1u % 1cB"
+#define SIZE_ARGS(a)	(a).val, (a).decimal, SIZE_SUFFIX[(a).magnitude]
+
+struct size_args {
+  u64 val:48;
+  u64 decimal:8;
+  u64 magnitude:8;
+};
+
+static struct size_args
+get_size_args(u64 val)
 {
-  char *px = " kMG";
-  int i = 0;
-  while ((val >= 10000) && (i < 3))
+#define VALDEC	10 /* One decimal place */
+  val *= VALDEC;
+
+  uint i = 0;
+  while ((val >= 10000 * VALDEC) && (i < 4))
     {
       val = (val + 512) / 1024;
       i++;
     }
 
-  cli_msg(-1018, "%-17s %4u %cB", dsc, (unsigned) val, px[i]);
+  return (struct size_args) {
+    .val = (val / VALDEC),
+    .decimal = (val % VALDEC),
+    .magnitude = i,
+  };
+}
+
+static void
+print_size(char *dsc, struct resmem vals)
+{
+  struct size_args effective = get_size_args(vals.effective);
+  struct size_args overhead = get_size_args(vals.overhead);
+
+  cli_msg(-1018, "%-17s " SIZE_FORMAT "   " SIZE_FORMAT, dsc, SIZE_ARGS(effective), SIZE_ARGS(overhead));
 }
 
 extern pool *rt_table_pool;
@@ -88,13 +113,14 @@ void
 cmd_show_memory(void)
 {
   cli_msg(-1018, "BIRD memory usage");
+  cli_msg(-1018, "%-17s Effective    Overhead", "");
   print_size("Routing tables:", rmemsize(rt_table_pool));
   print_size("Route attributes:", rmemsize(rta_pool));
   print_size("Protocols:", rmemsize(proto_pool));
-  size_t total = rmemsize(&root_pool);
+  struct resmem total = rmemsize(&root_pool);
 #ifdef HAVE_MMAP
-  print_size("Standby memory:", get_page_size() * pages_kept);
-  total += get_page_size() * pages_kept;
+  print_size("Standby memory:", (struct resmem) { .overhead = get_page_size() * pages_kept });
+  total.overhead += get_page_size() * pages_kept;
 #endif
   print_size("Total:", total);
   cli_msg(0, "");