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 <[email protected]>
---
Documentation/filesystems/proc.txt | 8 ++++++
Documentation/sysctl/vm.txt | 2 -
include/linux/sysctl.h | 1
include/linux/writeback.h | 2 +
kernel/sysctl.c | 9 +++++++
mm/filemap.c | 47 +++++++++++++++++++++++++++++++++++--
mm/page-writeback.c | 2 -
mm/swap.c | 3 --
8 files changed, 68 insertions(+), 6 deletions(-)
Index: linux-ck-dev/include/linux/writeback.h
===================================================================
--- linux-ck-dev.orig/include/linux/writeback.h 2006-06-18 15:20:10.000000000 +1000
+++ linux-ck-dev/include/linux/writeback.h 2006-06-18 15:25:25.000000000 +1000
@@ -85,6 +85,8 @@ void laptop_io_completion(void);
void laptop_sync_completion(void);
void throttle_vm_writeout(void);
+extern long total_pages;
+
/* These are exported to sysctl. */
extern int dirty_background_ratio;
extern int vm_dirty_ratio;
Index: linux-ck-dev/mm/filemap.c
===================================================================
--- linux-ck-dev.orig/mm/filemap.c 2006-06-18 15:20:10.000000000 +1000
+++ linux-ck-dev/mm/filemap.c 2006-06-18 15:25:25.000000000 +1000
@@ -434,6 +434,16 @@ 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(struct address_space *x)
{
@@ -783,6 +793,28 @@ grab_cache_page_nowait(struct address_sp
EXPORT_SYMBOL(grab_cache_page_nowait);
/*
+ * 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;
+
+/*
+ * 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 - read_page_state(nr_mapped);
+
+ if (nr_pages * 2 > unmapped_ram)
+ return 1;
+ }
+ return 0;
+}
+
+/*
* This is a generic file read routine, and uses the
* mapping->a_ops->readpage() function for the actual low-level
* stuff.
@@ -982,8 +1014,19 @@ 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-ck-dev/mm/page-writeback.c
===================================================================
--- linux-ck-dev.orig/mm/page-writeback.c 2006-06-18 15:25:22.000000000 +1000
+++ linux-ck-dev/mm/page-writeback.c 2006-06-18 15:25:25.000000000 +1000
@@ -45,7 +45,7 @@
*/
static long ratelimit_pages = 32;
-static long total_pages; /* The total number of pages in the machine. */
+long total_pages __read_mostly; /* The total number of pages in the machine. */
static int dirty_exceeded __cacheline_aligned_in_smp; /* Dirty mem may be over limit */
/*
Index: linux-ck-dev/mm/swap.c
===================================================================
--- linux-ck-dev.orig/mm/swap.c 2006-06-18 15:24:48.000000000 +1000
+++ linux-ck-dev/mm/swap.c 2006-06-18 15:25:25.000000000 +1000
@@ -416,8 +416,7 @@ 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-ck-dev/include/linux/sysctl.h
===================================================================
--- linux-ck-dev.orig/include/linux/sysctl.h 2006-06-18 15:24:58.000000000 +1000
+++ linux-ck-dev/include/linux/sysctl.h 2006-06-18 15:25:25.000000000 +1000
@@ -191,6 +191,7 @@ enum
VM_ZONE_RECLAIM_INTERVAL=32, /* time period to wait after reclaim failure */
VM_SWAP_PREFETCH=33, /* swap prefetch */
VM_HARDMAPLIMIT=34, /* Make mapped a hard limit */
+ VM_TAIL_LARGEFILES=35, /* Read large files to lru tail */
};
Index: linux-ck-dev/kernel/sysctl.c
===================================================================
--- linux-ck-dev.orig/kernel/sysctl.c 2006-06-18 15:24:58.000000000 +1000
+++ linux-ck-dev/kernel/sysctl.c 2006-06-18 15:25:25.000000000 +1000
@@ -73,6 +73,7 @@ extern int printk_ratelimit_burst;
extern int pid_max_min, pid_max_max;
extern int sysctl_drop_caches;
extern int percpu_pagelist_fraction;
+extern int vm_tail_largefiles;
#if defined(CONFIG_X86_LOCAL_APIC) && defined(CONFIG_X86)
int unknown_nmi_panic;
@@ -809,6 +810,14 @@ 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-ck-dev/Documentation/filesystems/proc.txt
===================================================================
--- linux-ck-dev.orig/Documentation/filesystems/proc.txt 2006-06-18 15:20:10.000000000 +1000
+++ linux-ck-dev/Documentation/filesystems/proc.txt 2006-06-18 15:25:25.000000000 +1000
@@ -1318,6 +1318,14 @@ 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-ck-dev/Documentation/sysctl/vm.txt
===================================================================
--- linux-ck-dev.orig/Documentation/sysctl/vm.txt 2006-06-18 15:24:58.000000000 +1000
+++ linux-ck-dev/Documentation/sysctl/vm.txt 2006-06-18 15:25:25.000000000 +1000
@@ -37,7 +37,7 @@ 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
--
-ck
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
