diff -urN oldtree/Documentation/filesystems/proc.txt newtree/Documentation/filesystems/proc.txt
--- oldtree/Documentation/filesystems/proc.txt	2006-09-29 14:03:18.000000000 -0400
+++ newtree/Documentation/filesystems/proc.txt	2006-09-29 14:57:40.000000000 -0400
@@ -1324,6 +1324,14 @@
 As this is a non-destructive operation and dirty objects are not freeable, the
 user should run `sync' first.
 
+tail_largefiles
+---------------
+
+When enabled reads from large files to the tail end of the inactive lru list.
+This means that any cache from reading large files is dropped very quickly,
+preventing loss of mapped ram and useful pagecache when large files are read.
+This does, however, make caching less effective when working with large files.
+
 
 2.5 /proc/sys/dev - Device specific parameters
 ----------------------------------------------
diff -urN oldtree/Documentation/sysctl/vm.txt newtree/Documentation/sysctl/vm.txt
--- oldtree/Documentation/sysctl/vm.txt	2006-09-29 14:51:43.000000000 -0400
+++ newtree/Documentation/sysctl/vm.txt	2006-09-29 14:57:40.000000000 -0400
@@ -39,7 +39,7 @@
 
 dirty_ratio, dirty_background_ratio, dirty_expire_centisecs,
 dirty_writeback_centisecs, vfs_cache_pressure, laptop_mode,
-block_dump, swap_token_timeout, drop-caches:
+block_dump, swap_token_timeout, drop-caches, tail_largefiles:
 
 See Documentation/filesystems/proc.txt
 
diff -urN oldtree/include/linux/sysctl.h newtree/include/linux/sysctl.h
--- oldtree/include/linux/sysctl.h	2006-09-29 14:51:44.000000000 -0400
+++ newtree/include/linux/sysctl.h	2006-09-29 14:58:54.000000000 -0400
@@ -199,6 +199,7 @@
 	VM_MIN_SLAB=35,		 /* Percent pages ignored by zone reclaim */
 	VM_SWAP_PREFETCH=36,	/* swap prefetch */
         VM_HARDMAPLIMIT=37,     /* Make mapped a hard limit */
+        VM_TAIL_LARGEFILES=38,  /* Read large files to lru tail */
 };
 
 
diff -urN oldtree/include/linux/writeback.h newtree/include/linux/writeback.h
--- oldtree/include/linux/writeback.h	2006-09-29 14:03:22.000000000 -0400
+++ newtree/include/linux/writeback.h	2006-09-29 14:57:40.000000000 -0400
@@ -87,6 +87,8 @@
 void throttle_vm_writeout(void);
 void writeback_congestion_end(void);
 
+extern long total_pages;
+
 /* These are exported to sysctl. */
 extern int dirty_background_ratio;
 extern int vm_dirty_ratio;
diff -urN oldtree/kernel/sysctl.c newtree/kernel/sysctl.c
--- oldtree/kernel/sysctl.c	2006-09-29 14:51:44.000000000 -0400
+++ newtree/kernel/sysctl.c	2006-09-29 14:58:20.000000000 -0400
@@ -74,6 +74,7 @@
 extern int sysctl_drop_caches;
 extern int percpu_pagelist_fraction;
 extern int compat_log;
+extern int vm_tail_largefiles;
 
 #if defined(CONFIG_X86_LOCAL_APIC) && defined(CONFIG_X86)
 int unknown_nmi_panic;
@@ -858,6 +859,14 @@
 		.mode		= 0644,
 		.proc_handler	= &proc_dointvec,
 	},
+	{
+		.ctl_name	= VM_TAIL_LARGEFILES,
+		.procname	= "tail_largefiles",
+		.data		= &vm_tail_largefiles,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= &proc_dointvec,
+	},
 #ifdef CONFIG_HUGETLB_PAGE
 	 {
 		.ctl_name	= VM_HUGETLB_PAGES,
diff -urN oldtree/mm/filemap.c newtree/mm/filemap.c
--- oldtree/mm/filemap.c	2006-09-29 14:03:22.000000000 -0400
+++ newtree/mm/filemap.c	2006-09-29 14:57:40.000000000 -0400
@@ -466,6 +466,16 @@
 	return ret;
 }
 
+int add_to_page_cache_lru_tail(struct page *page,
+	struct address_space *mapping, pgoff_t offset, gfp_t gfp_mask)
+{
+	int ret = add_to_page_cache(page, mapping, offset, gfp_mask);
+
+	if (ret == 0)
+		lru_cache_add_tail(page);
+	return ret;
+}
+
 #ifdef CONFIG_NUMA
 struct page *page_cache_alloc(struct address_space *x)
 {
@@ -868,6 +878,34 @@
 	ra->ra_pages /= 4;
 }
 
+/*
+ * Sysctl which determines whether we should read from large files to the
+ * tail of the inactive lru list.
+ */
+int vm_tail_largefiles __read_mostly = 1;
+
+static inline int nr_mapped(void)
+{
+	return global_page_state(NR_FILE_MAPPED) +
+		global_page_state(NR_ANON_PAGES);
+}
+
+/*
+ * This examines how large in pages a file size is and returns 1 if it is
+ * more than half the unmapped ram. Avoid doing read_page_state which is
+ * expensive unless we already know it is likely to be large enough.
+ */
+static int large_isize(unsigned long nr_pages)
+{
+	if (nr_pages * 6 > total_pages) {
+		 unsigned long unmapped_ram = total_pages - nr_mapped();
+
+		if (nr_pages * 2 > unmapped_ram)
+			return 1;
+	}
+	return 0;
+}
+
 /**
  * do_generic_mapping_read - generic file read routine
  * @mapping:	address_space to be read
@@ -1076,8 +1114,19 @@
 				goto out;
 			}
 		}
-		error = add_to_page_cache_lru(cached_page, mapping,
-						index, GFP_KERNEL);
+
+		/*
+		 * If we know the file is large we add the pages read to the
+		 * end of the lru as we're unlikely to be able to cache the
+		 * whole file in ram so make those pages the first to be
+		 * dropped if not referenced soon.
+		 */
+		if (vm_tail_largefiles && large_isize(end_index))
+			error = add_to_page_cache_lru_tail(cached_page,
+						mapping, index, GFP_KERNEL);
+		else
+			error = add_to_page_cache_lru(cached_page, mapping,
+							index, GFP_KERNEL);
 		if (error) {
 			if (error == -EEXIST)
 				goto find_page;
diff -urN oldtree/mm/swap.c newtree/mm/swap.c
--- oldtree/mm/swap.c	2006-09-29 14:16:42.000000000 -0400
+++ newtree/mm/swap.c	2006-09-29 14:57:40.000000000 -0400
@@ -434,8 +434,7 @@
 
 /*
  * Function used uniquely to put pages back to the lru at the end of the
- * inactive list to preserve the lru order. Currently only used by swap
- * prefetch.
+ * inactive list to preserve the lru order.
  */
 void fastcall lru_cache_add_tail(struct page *page)
 {
diff -urN oldtree/mm/vmscan.c newtree/mm/vmscan.c
--- oldtree/mm/vmscan.c	2006-09-29 14:55:45.000000000 -0400
+++ newtree/mm/vmscan.c	2006-09-29 14:57:40.000000000 -0400
@@ -115,7 +115,7 @@
  */
 int vm_mapped __read_mostly = 66;
 int vm_hardmaplimit __read_mostly = 1;
-long vm_total_pages;	/* The total number of pages which the VM controls */
+long vm_total_pages __read_mostly;	/* The total number of pages which the VM controls */
 
 static LIST_HEAD(shrinker_list);
 static DECLARE_RWSEM(shrinker_rwsem);