[malloc] Track maximum heap usage

Track the current and maximum heap usage, and display the maximum
during shutdown when DEBUG=malloc is enabled.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/core/malloc.c

 /** Total amount of free memory */
 size_t freemem;
 
+/** Total amount of used memory */
+size_t usedmem;
+
+/** Maximum amount of used memory */
+size_t maxusedmem;
+
 /**
  * Heap size
  *
 				VALGRIND_MAKE_MEM_NOACCESS ( pre,
 							     sizeof ( *pre ) );
 			}
-			/* Update total free memory */
+			/* Update memory usage statistics */
 			freemem -= actual_size;
+			usedmem += actual_size;
+			if ( usedmem > maxusedmem )
+				maxusedmem = usedmem;
 			/* Return allocated block */
 			DBGC2 ( &heap, "Allocated [%p,%p)\n", block,
 				( ( ( void * ) block ) + size ) );
 		VALGRIND_MAKE_MEM_NOACCESS ( block, sizeof ( *block ) );
 	}
 
-	/* Update free memory counter */
+	/* Update memory usage statistics */
 	freemem += actual_size;
+	usedmem -= actual_size;
 
 	check_blocks();
 	valgrind_make_blocks_noaccess();
  * @c start must be aligned to at least a multiple of sizeof(void*).
  */
 void mpopulate ( void *start, size_t len ) {
+
 	/* Prevent free_memblock() from rounding up len beyond the end
 	 * of what we were actually given...
 	 */
-	free_memblock ( start, ( len & ~( MIN_MEMBLOCK_SIZE - 1 ) ) );
+	len &= ~( MIN_MEMBLOCK_SIZE - 1 );
+
+	/* Add to allocation pool */
+	free_memblock ( start, len );
+
+	/* Fix up memory usage statistics */
+	usedmem += len;
 }
 
 /**
  */
 static void shutdown_cache ( int booting __unused ) {
 	discard_all_cache();
+	DBGC ( &heap, "Maximum heap usage %zdkB\n", ( maxusedmem >> 10 ) );
 }
 
 /** Memory allocator shutdown function */

src/include/ipxe/malloc.h

 #include <valgrind/memcheck.h>
 
 extern size_t freemem;
+extern size_t usedmem;
+extern size_t maxusedmem;
 
 extern void * __malloc alloc_memblock ( size_t size, size_t align,
 					size_t offset );