From CaT <cat@zip.com.au>
What this patch does is allow you to specify the max amount of memory tmpfs
can use as a percentage of available real ram. This (in my eyes) is useful
so that you do not have to remember to change the setting if you want
something other then 50% and some of your ram goes.
Hugh redid the arithmetic to not overflow at 4GB; the particular order of
lines helps RH's gcc-2.96-110 not to get confused in the do_div. 2.5 can use
totalram_pages. Update mount options in tmpfs Doc.
There's an argument that the percentage should be of ram+swap, that's what
Christoph originally intended. But we set the default at 50% of ram only, so
I believe it's more consistent to follow that precedent.
Documentation/filesystems/tmpfs.txt | 25 ++++++++++---------------
mm/shmem.c | 11 ++++++++---
2 files changed, 18 insertions(+), 18 deletions(-)
diff -puN Documentation/filesystems/tmpfs.txt~tmpfs-6-percentile-sizing Documentation/filesystems/tmpfs.txt
--- 25/Documentation/filesystems/tmpfs.txt~tmpfs-6-percentile-sizing 2003-04-02 22:51:13.000000000 -0800
+++ 25-akpm/Documentation/filesystems/tmpfs.txt 2003-04-02 22:51:13.000000000 -0800
@@ -54,18 +54,21 @@ tmpfs has the following uses:
4) And probably a lot more I do not know about :-)
-tmpfs has a couple of mount options:
+tmpfs has three mount options for sizing:
-size: The limit of allocated bytes for this tmpfs instance. The
+size: The limit of allocated bytes for this tmpfs instance. The
default is half of your physical RAM without swap. If you
- oversize your tmpfs instances the machine will deadlock
- since the OOM handler will not be able to free that memory.
-nr_blocks: The same as size, but in blocks of PAGECACHE_SIZE.
+ oversize your tmpfs instances the machine will deadlock
+ since the OOM handler will not be able to free that memory.
+nr_blocks: The same as size, but in blocks of PAGE_CACHE_SIZE.
nr_inodes: The maximum number of inodes for this instance. The default
is half of the number of your physical RAM pages.
These parameters accept a suffix k, m or g for kilo, mega and giga and
-can be changed on remount.
+can be changed on remount. The size parameter also accepts a suffix %
+to limit this tmpfs instance to that percentage of your physical RAM:
+the default, when neither size nor nr_blocks is specified, is size=50%
+
To specify the initial root directory you can use the following mount
options:
@@ -83,15 +86,7 @@ will give you tmpfs instance on /mytmpfs
RAM/SWAP in 10240 inodes and it is only accessible by root.
-TODOs:
-
-1) give the size option a percent semantic: If you give a mount option
- size=50% the tmpfs instance should be able to grow to 50 percent of
- RAM + swap. So the instance should adapt automatically if you add
- or remove swap space.
-2) Show the number of tmpfs RAM pages. (As shared?)
-
Author:
Christoph Rohland <cr@sap.com>, 1.12.01
Updated:
- Hugh Dickins <hugh@veritas.com>, 17 Oct 2002
+ Hugh Dickins <hugh@veritas.com>, 01 April 2003
diff -puN mm/shmem.c~tmpfs-6-percentile-sizing mm/shmem.c
--- 25/mm/shmem.c~tmpfs-6-percentile-sizing 2003-04-02 22:51:13.000000000 -0800
+++ 25-akpm/mm/shmem.c 2003-04-02 22:51:13.000000000 -0800
@@ -35,6 +35,7 @@
#include <linux/vfs.h>
#include <linux/blkdev.h>
#include <asm/uaccess.h>
+#include <asm/div64.h>
/* This magic number is used in glibc for posix shared memory */
#define TMPFS_MAGIC 0x01021994
@@ -1587,6 +1588,12 @@ static int shmem_parse_options(char *opt
if (!strcmp(this_char,"size")) {
unsigned long long size;
size = memparse(value,&rest);
+ if (*rest == '%') {
+ size <<= PAGE_SHIFT;
+ size *= totalram_pages;
+ do_div(size, 100);
+ rest++;
+ }
if (*rest)
goto bad_val;
*blocks = size >> PAGE_CACHE_SHIFT;
@@ -1652,7 +1659,6 @@ static int shmem_fill_super(struct super
uid_t uid = current->fsuid;
gid_t gid = current->fsgid;
struct shmem_sb_info *sbinfo;
- struct sysinfo si;
int err = -ENOMEM;
sbinfo = kmalloc(sizeof(struct shmem_sb_info), GFP_KERNEL);
@@ -1665,8 +1671,7 @@ static int shmem_fill_super(struct super
* Per default we only allow half of the physical ram per
* tmpfs instance
*/
- si_meminfo(&si);
- blocks = inodes = si.totalram / 2;
+ blocks = inodes = totalram_pages / 2;
#ifdef CONFIG_TMPFS
if (shmem_parse_options(data, &mode, &uid, &gid, &blocks, &inodes)) {
_