kernel26-alx/patches-2.6.20-r6/0022-2.6.20-mm-filesize_dependant_lru_cache_add.patch

When reading from large files through the generic file read functions into
page cache we can detect when a file is so large that it is unlikely to be
fully cached in ram.

Add a tunable /proc/sys/vm/tail_largefiles that puts them at the tail of the
inactive list to minimise their harm on present mapped pages and pagecache
and enable it by default.

Signed-off-by: Con Kolivas <kernel@kolivas.org>

---
 Documentation/filesystems/proc.txt |    8 +++++
 Documentation/sysctl/vm.txt        |    2 -
 include/linux/sysctl.h             |    1 
 kernel/sysctl.c                    |    9 ++++++
 mm/filemap.c                       |   53 +++++++++++++++++++++++++++++++++++--
 mm/swap.c                          |    3 --
 6 files changed, 71 insertions(+), 5 deletions(-)

Index: linux-2.6.20-ck1/mm/filemap.c
===================================================================
--- linux-2.6.20-ck1.orig/mm/filemap.c	2007-02-05 22:52:04.000000000 +1100
+++ linux-2.6.20-ck1/mm/filemap.c	2007-02-16 19:01:34.000000000 +1100
@@ -466,6 +466,16 @@ int add_to_page_cache_lru(struct page *p
 	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(gfp_t gfp)
 {
@@ -856,6 +866,34 @@ static void shrink_readahead_size_eio(st
 	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 > vm_total_pages) {
+		 unsigned long unmapped_ram = vm_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
@@ -1064,8 +1102,19 @@ no_cached_page:
 				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;
Index: linux-2.6.20-ck1/mm/swap.c
===================================================================
--- linux-2.6.20-ck1.orig/mm/swap.c	2007-02-16 19:01:33.000000000 +1100
+++ linux-2.6.20-ck1/mm/swap.c	2007-02-16 19:01:34.000000000 +1100
@@ -434,8 +434,7 @@ void __pagevec_lru_add_active(struct pag
 
 /*
  * 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)
 {
Index: linux-2.6.20-ck1/kernel/sysctl.c
===================================================================
--- linux-2.6.20-ck1.orig/kernel/sysctl.c	2007-02-16 19:01:33.000000000 +1100
+++ linux-2.6.20-ck1/kernel/sysctl.c	2007-02-16 19:01:34.000000000 +1100
@@ -77,6 +77,7 @@ extern int pid_max_min, pid_max_max;
 extern int sysctl_drop_caches;
 extern int percpu_pagelist_fraction;
 extern int compat_log;
+extern int vm_tail_largefiles;
 
 /* this is needed for the proc_dointvec_minmax for [fs_]overflow UID and GID */
 static int maxolduid = 65535;
@@ -918,6 +919,14 @@ static ctl_table vm_table[] = {
 		.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,
Index: linux-2.6.20-ck1/Documentation/filesystems/proc.txt
===================================================================
--- linux-2.6.20-ck1.orig/Documentation/filesystems/proc.txt	2007-02-05 22:51:59.000000000 +1100
+++ linux-2.6.20-ck1/Documentation/filesystems/proc.txt	2007-02-16 19:01:34.000000000 +1100
@@ -1324,6 +1324,14 @@ To free pagecache, dentries and inodes:
 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
 ----------------------------------------------
Index: linux-2.6.20-ck1/Documentation/sysctl/vm.txt
===================================================================
--- linux-2.6.20-ck1.orig/Documentation/sysctl/vm.txt	2007-02-16 19:01:33.000000000 +1100
+++ linux-2.6.20-ck1/Documentation/sysctl/vm.txt	2007-02-16 19:01:34.000000000 +1100
@@ -39,7 +39,7 @@ Currently, these files are in /proc/sys/
 
 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
 
Index: linux-2.6.20-ck1/include/linux/sysctl.h
===================================================================
--- linux-2.6.20-ck1.orig/include/linux/sysctl.h	2007-02-16 19:01:33.000000000 +1100
+++ linux-2.6.20-ck1/include/linux/sysctl.h	2007-02-16 19:01:34.000000000 +1100
@@ -204,6 +204,7 @@ enum
 	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 */
 };
 
 
1	When reading from large files through the generic file read functions into
2	page cache we can detect when a file is so large that it is unlikely to be
3	fully cached in ram.
4
5	Add a tunable /proc/sys/vm/tail_largefiles that puts them at the tail of the
6	inactive list to minimise their harm on present mapped pages and pagecache
7	and enable it by default.
8
9	Signed-off-by: Con Kolivas <kernel@kolivas.org>
10
11	---
12	Documentation/filesystems/proc.txt \| 8 +++++
13	Documentation/sysctl/vm.txt \| 2 -
14	include/linux/sysctl.h \| 1
15	kernel/sysctl.c \| 9 ++++++
16	mm/filemap.c \| 53 +++++++++++++++++++++++++++++++++++--
17	mm/swap.c \| 3 --
18	6 files changed, 71 insertions(+), 5 deletions(-)
19
20	Index: linux-2.6.20-ck1/mm/filemap.c
21	===================================================================
22	--- linux-2.6.20-ck1.orig/mm/filemap.c 2007-02-05 22:52:04.000000000 +1100
23	+++ linux-2.6.20-ck1/mm/filemap.c 2007-02-16 19:01:34.000000000 +1100
24	@@ -466,6 +466,16 @@ int add_to_page_cache_lru(struct page *p
25	return ret;
26	}
27
28	+int add_to_page_cache_lru_tail(struct page *page,
29	+ struct address_space *mapping, pgoff_t offset, gfp_t gfp_mask)
30	+{
31	+ int ret = add_to_page_cache(page, mapping, offset, gfp_mask);
32	+
33	+ if (ret == 0)
34	+ lru_cache_add_tail(page);
35	+ return ret;
36	+}
37	+
38	#ifdef CONFIG_NUMA
39	struct page *__page_cache_alloc(gfp_t gfp)
40	{
41	@@ -856,6 +866,34 @@ static void shrink_readahead_size_eio(st
42	ra->ra_pages /= 4;
43	}
44
45	+/*
46	+ * Sysctl which determines whether we should read from large files to the
47	+ * tail of the inactive lru list.
48	+ */
49	+int vm_tail_largefiles __read_mostly = 1;
50	+
51	+static inline int nr_mapped(void)
52	+{
53	+ return global_page_state(NR_FILE_MAPPED) +
54	+ global_page_state(NR_ANON_PAGES);
55	+}
56	+
57	+/*
58	+ * This examines how large in pages a file size is and returns 1 if it is
59	+ * more than half the unmapped ram. Avoid doing read_page_state which is
60	+ * expensive unless we already know it is likely to be large enough.
61	+ */
62	+static int large_isize(unsigned long nr_pages)
63	+{
64	+ if (nr_pages * 6 > vm_total_pages) {
65	+ unsigned long unmapped_ram = vm_total_pages - nr_mapped();
66	+
67	+ if (nr_pages * 2 > unmapped_ram)
68	+ return 1;
69	+ }
70	+ return 0;
71	+}
72	+
73	/**
74	* do_generic_mapping_read - generic file read routine
75	* @mapping: address_space to be read
76	@@ -1064,8 +1102,19 @@ no_cached_page:
77	goto out;
78	}
79	}
80	- error = add_to_page_cache_lru(cached_page, mapping,
81	- index, GFP_KERNEL);
82	+
83	+ /*
84	+ * If we know the file is large we add the pages read to the
85	+ * end of the lru as we're unlikely to be able to cache the
86	+ * whole file in ram so make those pages the first to be
87	+ * dropped if not referenced soon.
88	+ */
89	+ if (vm_tail_largefiles && large_isize(end_index))
90	+ error = add_to_page_cache_lru_tail(cached_page,
91	+ mapping, index, GFP_KERNEL);
92	+ else
93	+ error = add_to_page_cache_lru(cached_page, mapping,
94	+ index, GFP_KERNEL);
95	if (error) {
96	if (error == -EEXIST)
97	goto find_page;
98	Index: linux-2.6.20-ck1/mm/swap.c
99	===================================================================
100	--- linux-2.6.20-ck1.orig/mm/swap.c 2007-02-16 19:01:33.000000000 +1100
101	+++ linux-2.6.20-ck1/mm/swap.c 2007-02-16 19:01:34.000000000 +1100
102	@@ -434,8 +434,7 @@ void __pagevec_lru_add_active(struct pag
103
104	/*
105	* Function used uniquely to put pages back to the lru at the end of the
106	- * inactive list to preserve the lru order. Currently only used by swap
107	- * prefetch.
108	+ * inactive list to preserve the lru order.
109	*/
110	void fastcall lru_cache_add_tail(struct page *page)
111	{
112	Index: linux-2.6.20-ck1/kernel/sysctl.c
113	===================================================================
114	--- linux-2.6.20-ck1.orig/kernel/sysctl.c 2007-02-16 19:01:33.000000000 +1100
115	+++ linux-2.6.20-ck1/kernel/sysctl.c 2007-02-16 19:01:34.000000000 +1100
116	@@ -77,6 +77,7 @@ extern int pid_max_min, pid_max_max;
117	extern int sysctl_drop_caches;
118	extern int percpu_pagelist_fraction;
119	extern int compat_log;
120	+extern int vm_tail_largefiles;
121
122	/* this is needed for the proc_dointvec_minmax for [fs_]overflow UID and GID */
123	static int maxolduid = 65535;
124	@@ -918,6 +919,14 @@ static ctl_table vm_table[] = {
125	.mode = 0644,
126	.proc_handler = &proc_dointvec,
127	},
128	+ {
129	+ .ctl_name = VM_TAIL_LARGEFILES,
130	+ .procname = "tail_largefiles",
131	+ .data = &vm_tail_largefiles,
132	+ .maxlen = sizeof(int),
133	+ .mode = 0644,
134	+ .proc_handler = &proc_dointvec,
135	+ },
136	#ifdef CONFIG_HUGETLB_PAGE
137	{
138	.ctl_name = VM_HUGETLB_PAGES,
139	Index: linux-2.6.20-ck1/Documentation/filesystems/proc.txt
140	===================================================================
141	--- linux-2.6.20-ck1.orig/Documentation/filesystems/proc.txt 2007-02-05 22:51:59.000000000 +1100
142	+++ linux-2.6.20-ck1/Documentation/filesystems/proc.txt 2007-02-16 19:01:34.000000000 +1100
143	@@ -1324,6 +1324,14 @@ To free pagecache, dentries and inodes:
144	As this is a non-destructive operation and dirty objects are not freeable, the
145	user should run `sync' first.
146
147	+tail_largefiles
148	+---------------
149	+
150	+When enabled reads from large files to the tail end of the inactive lru list.
151	+This means that any cache from reading large files is dropped very quickly,
152	+preventing loss of mapped ram and useful pagecache when large files are read.
153	+This does, however, make caching less effective when working with large files.
154	+
155
156	2.5 /proc/sys/dev - Device specific parameters
157	----------------------------------------------
158	Index: linux-2.6.20-ck1/Documentation/sysctl/vm.txt
159	===================================================================
160	--- linux-2.6.20-ck1.orig/Documentation/sysctl/vm.txt 2007-02-16 19:01:33.000000000 +1100
161	+++ linux-2.6.20-ck1/Documentation/sysctl/vm.txt 2007-02-16 19:01:34.000000000 +1100
162	@@ -39,7 +39,7 @@ Currently, these files are in /proc/sys/
163
164	dirty_ratio, dirty_background_ratio, dirty_expire_centisecs,
165	dirty_writeback_centisecs, vfs_cache_pressure, laptop_mode,
166	-block_dump, swap_token_timeout, drop-caches:
167	+block_dump, swap_token_timeout, drop-caches, tail_largefiles:
168
169	See Documentation/filesystems/proc.txt
170
171	Index: linux-2.6.20-ck1/include/linux/sysctl.h
172	===================================================================
173	--- linux-2.6.20-ck1.orig/include/linux/sysctl.h 2007-02-16 19:01:33.000000000 +1100
174	+++ linux-2.6.20-ck1/include/linux/sysctl.h 2007-02-16 19:01:34.000000000 +1100
175	@@ -204,6 +204,7 @@ enum
176	VM_MIN_SLAB=35, /* Percent pages ignored by zone reclaim */
177	VM_SWAP_PREFETCH=36, /* swap prefetch */
178	VM_HARDMAPLIMIT=37, /* Make mapped a hard limit */
179	+ VM_TAIL_LARGEFILES=38, /* Read large files to lru tail */
180	};
181
182