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Subject[RFC/T 0/6] sysfs backing store (with symlink)
Hi All,

Please find following patches for sysfs-backing store. This version has
support for putting symlinks also on backing store. Earlier it has support
for text/binary attribute files.

http://marc.theaimsgroup.com/?l=linux-kernel&m=107269078726254&w=2

Apart from a few bug fixes, the main change in this version is for symlinks.
sysfs_create_link() now does not create dentry/inode for the link, but
allocates a sysfs_dirent and adds it the parent sysfs_dirent's s_children
list. dentry/inode for the link is created when the symlink is first looked up.

I request Martin and Mackall to _replace_ the old patch set with the
new one in their trees.

With this we save approx 75-80% of lowmem requirements of sysfs. Symlinks
support is needed for S390 linux people as they create lots of symlinks. I
have some numbers collected on S390 machine after creating 4096 ctc devices.
This created around 62433 sysfs entries. Backing store saves around 145 MB
of Lowmem when sysfs files are not in use.

---------------------------------------------------------------------------
Without sysfs backing store
# cat /proc/sys/fs/dentry-state
66733 4100 45 0 0 0
# grep LowFree /proc/meminfo
LowFree: 20984 kB

# grep dentry /proc/slabinfo; grep -w inode_cache /proc/slabinfo
dentry_cache 66750 66750 256 15 1 : tunables 120 60 8 : slabdata 4450 4450 0
inode_cache 62480 62480 768 5 1 : tunables 54 27 8 : slabdata 12496 12496 0

---------------------------------------------------------------------------
---------------------------------------------------------------------------
With sysfs backing store
# cat /proc/sys/fs/dentry-state
8783 155 45 0 0 0
# grep LowFree /proc/meminfo
LowFree: 166416 kB

# grep dentry /proc/slabinfo; grep -w inode_cache /proc/slabinfo
dentry_cache 8795 8880 256 15 1 : tunables 120 60 8 : slabdata 592 592 0
inode_cache 8495 8495 768 5 1 : tunables 54 27 8 : slabdata 1699 1699 0

**** Savings of around 145 MB of Lowmem *****
---------------------------------------------------------------------------
Thanks
Maneesh
--
Maneesh Soni
Linux Technology Center,
IBM Software Lab, Bangalore, India
email: maneesh@in.ibm.com
Phone: 91-80-5044999 Fax: 91-80-5268553
T/L : 9243696
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