Applied patch by Rene Gollent:

* Add a cached_pages field to the system_info structure, and change the
  meaning of the used_pages field to not include cached pages.
* Provide the needed info using the new calls vm_get_available_memory(),
  and vm_page_num_available_pages().


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@24571 a95241bf-73f2-0310-859d-f6bbb57e9c96

headers/os/kernel/OS.h

@@ -657,7 +657,8 @@ typedef struct {
 	int64			kernel_version;             			/* version of this kernel */
 
 	bigtime_t		_busy_wait_time;			/* reserved for whatever */
-	int32			pad[4];   	               	/* just in case... */
+	int32			cached_pages;
+	int32			pad[3];   	               	/* just in case... */
 } system_info;
 
 /* system private, use macro instead */

headers/private/kernel/vm.h

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2007, Axel Dörfler, [email protected]. All rights reserved.
+ * Copyright 2002-2008, Axel Dörfler, [email protected]. All rights reserved.
  * Distributed under the terms of the MIT License.
  *
  * Copyright 2001-2002, Travis Geiselbrecht. All rights reserved.
@@ -138,6 +138,8 @@ status_t vm_map_page(struct vm_area *area, struct vm_page *page, addr_t address,
 status_t vm_get_physical_page(addr_t paddr, addr_t *vaddr, uint32 flags);
 status_t vm_put_physical_page(addr_t vaddr);
 
+off_t vm_get_available_memory(void);
+
 // user syscalls
 area_id _user_create_area(const char *name, void **address, uint32 addressSpec,
 			size_t size, uint32 lock, uint32 protection);

headers/private/kernel/vm_page.h

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2007, Axel Dörfler, [email protected].
+ * Copyright 2002-2008, Axel Dörfler, [email protected].
  * Distributed under the terms of the MIT License.
  *
  * Copyright 2001-2002, Travis Geiselbrecht. All rights reserved.
@@ -33,6 +33,7 @@ void vm_page_requeue(struct vm_page *page, bool tail);
 // get some data about the number of pages in the system
 size_t vm_page_num_pages(void);
 size_t vm_page_num_free_pages(void);
+size_t vm_page_num_available_pages(void);
 
 status_t vm_page_write_modified_pages(struct vm_cache *cache, bool fsReenter);
 void vm_page_schedule_write_page(struct vm_page *page);

src/bin/sysinfo.c

@@ -517,9 +517,10 @@ dump_cpus(system_info *info)
 static void
 dump_mem(system_info *info)
 {
-	printf("%10lu bytes free      (used/max %10lu / %10lu)\n",
+	printf("%10lu bytes free      (used/cached/max %10lu / %10lu / %10lu)\n",
 		B_PAGE_SIZE * (uint32)(info->max_pages - info->used_pages),
 		B_PAGE_SIZE * (uint32)info->used_pages,
+		B_PAGE_SIZE * (uint32)info->cached_pages,
 		B_PAGE_SIZE * (uint32)info->max_pages);
 }
 

src/system/kernel/system_info.cpp

@@ -79,8 +79,9 @@ _get_system_info(system_info *info, size_t size)
 
 	// ToDo: Add page_faults
 	info->max_pages = vm_page_num_pages();
-	info->used_pages = vm_page_num_pages() - vm_page_num_free_pages();
-
+	info->used_pages = vm_page_num_pages() - vm_page_num_available_pages();
+	info->cached_pages = vm_page_num_pages() - vm_page_num_free_pages()
+		- info->used_pages;
 	info->used_threads = thread_used_threads();
 	info->max_threads = thread_max_threads();
 	info->used_teams = team_used_teams();

src/system/kernel/vm/vm.cpp

@@ -4363,6 +4363,13 @@ vm_get_physical_page(addr_t paddr, addr_t *_vaddr, uint32 flags)
 }
 
 
+off_t
+vm_get_available_memory(void)
+{
+	return sAvailableMemory;
+}
+
+
 status_t
 vm_put_physical_page(addr_t vaddr)
 {

src/system/kernel/vm/vm_page.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2007, Axel Dörfler, axeld@pinc-software.de.
+ * Copyright 2002-2008, Axel Dörfler, axeld@pinc-software.de.
  * Distributed under the terms of the MIT License.
  *
  * Copyright 2001-2002, Travis Geiselbrecht. All rights reserved.
@@ -1830,6 +1830,20 @@ vm_page_num_pages(void)
 }
 
 
+/*! There is a subtle distinction between the page counts returned by
+	this function and vm_page_num_free_pages():
+	The latter returns the number of pages that are completely uncommitted,
+	whereas this one returns the number of pages that are available for
+	use by being reclaimed as well (IOW it factors in things like cache pages
+	as available).
+*/
+size_t
+vm_page_num_available_pages(void)
+{
+	return vm_get_available_memory() / B_PAGE_SIZE;
+}
+
+
 size_t
 vm_page_num_free_pages(void)
 {