Page allocator moved from pools to IO loops.

The resource pool system is highly hierarchical and keeping spare pages
in pools leads to unnecessarily complex memory management.

Loops have a flat hiearchy, at least for now, and it is therefore much
easier to keep care of pages, especially in cases of excessive virtual memory
fragmentation.

sysdep/unix/io-loop.h

@@ -7,6 +7,20 @@
 #ifndef _BIRD_SYSDEP_UNIX_IO_LOOP_H_
 #define _BIRD_SYSDEP_UNIX_IO_LOOP_H_
 
+#include "nest/bird.h"
+
+#include "lib/lists.h"
+#include "lib/event.h"
+#include "lib/timer.h"
+
+struct free_pages
+{
+  list list;		/* List of empty pages */
+  event *cleanup;	/* Event to call when number of pages is outside bounds */
+  u16 min, max;		/* Minimal and maximal number of free pages kept */
+  uint cnt;		/* Number of empty pages */
+};
+
 struct birdloop
 {
   resource r;
@@ -29,10 +43,17 @@ struct birdloop
 
   uint links;
 
+  struct free_pages pages;
+
   void (*stopped)(void *data);
   void *stop_data;
 
   struct birdloop *prev_loop;
 };
 
+extern _Thread_local struct birdloop *birdloop_current;
+
+void init_pages(struct birdloop *loop);
+void flush_pages(struct birdloop *loop);
+
 #endif