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5160ee6fc8
linux/fs
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Eric Dumazet 5160ee6fc8 [PATCH] shrink dentry struct 
Some long time ago, dentry struct was carefully tuned so that on 32 bits
UP, sizeof(struct dentry) was exactly 128, ie a power of 2, and a multiple
of memory cache lines.

Then RCU was added and dentry struct enlarged by two pointers, with nice
results for SMP, but not so good on UP, because breaking the above tuning
(128 + 8 = 136 bytes)

This patch reverts this unwanted side effect, by using an union (d_u),
where d_rcu and d_child are placed so that these two fields can share their
memory needs.

At the time d_free() is called (and d_rcu is really used), d_child is known
to be empty and not touched by the dentry freeing.

Lockless lookups only access d_name, d_parent, d_lock, d_op, d_flags (so
the previous content of d_child is not needed if said dentry was unhashed
but still accessed by a CPU because of RCU constraints)

As dentry cache easily contains millions of entries, a size reduction is
worth the extra complexity of the ugly C union.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Cc: Dipankar Sarma <dipankar@in.ibm.com>
Cc: Maneesh Soni <maneesh@in.ibm.com>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Cc: Ian Kent <raven@themaw.net>
Cc: Paul Jackson <pj@sgi.com>
Cc: Al Viro <viro@ftp.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Cc: Neil Brown <neilb@cse.unsw.edu.au>
Cc: James Morris <jmorris@namei.org>
Cc: Stephen Smalley <sds@epoch.ncsc.mil>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-08 20:13:58 -08:00
..
9p [PATCH] Fix and add EXPORT_SYMBOL(filemap_write_and_wait) 2006-01-08 20:13:47 -08:00
adfs [PATCH] changing CONFIG_LOCALVERSION rebuilds too much, for no good reason 2005-11-09 07:55:57 -08:00
affs [PATCH] kfree cleanup: fs 2005-11-07 07:54:06 -08:00
afs [PATCH] fix possible PAGE_CACHE_SHIFT overflows 2006-01-08 20:13:54 -08:00
autofs [PATCH] kfree cleanup: fs 2005-11-07 07:54:06 -08:00
autofs4 [PATCH] shrink dentry struct 2006-01-08 20:13:58 -08:00
befs remove unused fs/befs/attribute.c 2005-11-08 16:54:53 +01:00
bfs [PATCH] bfs iget() abuses 2005-10-04 13:22:01 -07:00
cifs [PATCH] Fix and add EXPORT_SYMBOL(filemap_write_and_wait) 2006-01-08 20:13:47 -08:00
coda [PATCH] shrink dentry struct 2006-01-08 20:13:58 -08:00
configfs [PATCH] configfs: User-driven configuration filesystem 2006-01-03 11:45:28 -08:00
cramfs [PATCH] fs/cramfs/uncompress.c should #include <linux/cramfs_fs.h> 2005-09-10 10:06:35 -07:00
debugfs [PATCH] remove duplicate get_dentry functions in various places 2005-06-23 09:45:20 -07:00
devfs [PATCH] kfree cleanup: fs 2005-11-07 07:54:06 -08:00
devpts [PATCH] Generic VFS fallback for security xattrs 2005-09-05 00:05:52 -07:00
efs
exportfs
ext2 [PATCH] ext2: remove duplicate newlines in ext2_fill_super 2005-11-13 18:14:17 -08:00
ext3 [PATCH] ext3: use sbi instead of EXT3_SB() in resize code. 2006-01-08 20:13:56 -08:00
fat [PATCH] fat: support a truncate() for expanding size (generic_cont_expand) 2006-01-08 20:13:47 -08:00
freevxfs [PATCH] fix possible PAGE_CACHE_SHIFT overflows 2006-01-08 20:13:54 -08:00
fuse [PATCH] fuse: check file type in lookup 2006-01-06 08:33:56 -08:00
hfs [PATCH] changing CONFIG_LOCALVERSION rebuilds too much, for no good reason 2005-11-09 07:55:57 -08:00
hfsplus [PATCH] hfsplus oops fix 2006-01-06 08:33:20 -08:00
hostfs [PATCH] uml: hostfs - fix possible PAGE_CACHE_SHIFT overflows 2005-12-29 09:48:15 -08:00
hpfs [PATCH] hpfs: remove spurious mtime update 2005-11-09 07:55:57 -08:00
hppfs [PATCH] hppfs: fix symlink error path 2005-08-26 11:39:19 -07:00
hugetlbfs [PATCH] Hugetlb: Copy on Write support 2006-01-06 08:33:23 -08:00
isofs [PATCH] kfree cleanup: fs 2005-11-07 07:54:06 -08:00
jbd [PATCH] jbd: split checkpoint lists 2006-01-06 08:33:59 -08:00
jffs [PATCH] fix possible PAGE_CACHE_SHIFT overflows 2006-01-08 20:13:54 -08:00
jffs2 [JFFS2] Fix the slab cache constructor of 'struct jffs2_inode_info' objects. 2005-11-29 16:57:17 +01:00
jfs [PATCH] Fix and add EXPORT_SYMBOL(filemap_write_and_wait) 2006-01-08 20:13:47 -08:00
lockd SUNRPC: get rid of cl_chatty 2006-01-06 14:58:56 -05:00
minix [PATCH] update filesystems for new delete_inode behavior 2005-09-09 13:57:27 -07:00
msdos [PATCH] fat: remove the unneeded vfat_find() in vfat_rename() 2005-10-30 17:37:32 -08:00
ncpfs [PATCH] shrink dentry struct 2006-01-08 20:13:58 -08:00
nfs [PATCH] nfsroot: do not silently stop parsing on an unknown option 2006-01-08 20:13:57 -08:00
nfs_common [PATCH] nfsacl: Solaris VxFS compatibility fix 2005-10-11 09:46:54 -07:00
nfsd SUNRPC: get rid of cl_chatty 2006-01-06 14:58:56 -05:00
nls
ntfs update the email address of Randy Dunlap 2006-01-03 13:37:51 +01:00
ocfs2 [PATCH] This patch contains the following cleanups: 2006-01-03 11:45:55 -08:00
openpromfs [PATCH] kfree cleanup: fs 2005-11-07 07:54:06 -08:00
partitions [PATCH] s390: cleanup Kconfig 2006-01-06 08:33:53 -08:00
proc [PATCH] slob: introduce the SLOB allocator 2006-01-08 20:13:41 -08:00
qnx4 fs/qnx4/bitmap.c: #if 0 qnx4_new_block() 2006-01-03 13:21:37 +01:00
ramfs [PATCH] NOMMU: Provide shared-writable mmap support on ramfs 2006-01-06 08:33:32 -08:00
reiserfs s/retreiv/retriev/g 2006-01-03 13:27:11 +01:00
relayfs [PATCH] relayfs: cleanup, change relayfs_file_* to relay_file_* 2006-01-08 20:13:51 -08:00
romfs [PATCH] fix possible PAGE_CACHE_SHIFT overflows 2006-01-08 20:13:54 -08:00
smbfs [PATCH] shrink dentry struct 2006-01-08 20:13:58 -08:00
sysfs [PATCH] sysfs: handle failures in sysfs_make_dirent 2006-01-04 16:18:09 -08:00
sysv [PATCH] fix possible PAGE_CACHE_SHIFT overflows 2006-01-08 20:13:54 -08:00
udf [PATCH] udf: remove bogus inode == NULL check in inode_bmap 2006-01-08 20:13:51 -08:00
ufs [PATCH] fs/ufs: debug mode compilation failure 2006-01-06 15:22:28 -08:00
vfat [PATCH] fat: remove the unneeded vfat_find() in vfat_rename() 2005-10-30 17:37:32 -08:00
xfs [PATCH] Fix and add EXPORT_SYMBOL(filemap_write_and_wait) 2006-01-08 20:13:47 -08:00
aio.c [PATCH] rcu file: use atomic primitives 2006-01-08 20:13:48 -08:00
attr.c [PATCH] Fix some problems with truncate and mtime semantics. 2006-01-08 20:13:52 -08:00
bad_inode.c
binfmt_aout.c [PATCH] mm: mm_init set_mm_counters 2005-10-29 21:40:38 -07:00
binfmt_elf_fdpic.c [PATCH] kfree cleanup: fs 2005-11-07 07:54:06 -08:00
binfmt_elf.c [PATCH] kfree cleanup: fs 2005-11-07 07:54:06 -08:00
binfmt_em86.c
binfmt_flat.c [PATCH] mm: mm_init set_mm_counters 2005-10-29 21:40:38 -07:00
binfmt_misc.c [PATCH] add a file_permission helper 2005-11-09 07:55:59 -08:00
binfmt_script.c
binfmt_som.c [PATCH] mm: mm_init set_mm_counters 2005-10-29 21:40:38 -07:00
bio.c [BLOCK] bio: check for same page merge possibilities in __bio_add_page() 2006-01-06 09:43:28 +01:00
block_dev.c [PATCH] block: add unlocked_ioctl support for block devices 2005-06-23 09:45:32 -07:00
buffer.c [PATCH] fix possible PAGE_CACHE_SHIFT overflows 2006-01-08 20:13:54 -08:00
char_dev.c [PATCH] cdev: cdev_put oops 2005-07-12 16:01:02 -07:00
compat_ioctl.c [COMPAT] net: SIOCGIFCONF data corruption 2005-11-20 13:41:59 -08:00
compat.c [PATCH] Fix overflow tests for compat_sys_fcntl64 locking 2006-01-08 20:13:52 -08:00
dcache.c [PATCH] shrink dentry struct 2006-01-08 20:13:58 -08:00
dcookies.c [PATCH] dcookies.c: use proper refcounting functions 2005-07-07 18:23:52 -07:00
direct-io.c [PATCH] core remove PageReserved 2005-10-29 21:40:39 -07:00
dnotify.c
dquot.c [PATCH] Fix oops in vfs_quotaon_mount() 2005-11-28 14:42:26 -08:00
drop_caches.c [PATCH] drop-pagecache 2006-01-08 20:12:40 -08:00
eventpoll.c [PATCH] epoll: handle timeout overflow 2005-09-28 07:46:41 -07:00
exec.c [PATCH] do_coredump() should reset group_stop_count earlier 2006-01-08 20:13:55 -08:00
fcntl.c [PATCH] sigio: cleanup, don't take tasklist twice 2006-01-08 20:13:57 -08:00
fifo.c
file_table.c [PATCH] rcu file: use atomic primitives 2006-01-08 20:13:48 -08:00
file.c [PATCH] Fix the fdtable freeing in the case of vmalloced fdset/arrays 2005-09-14 12:38:26 -07:00
filesystems.c [PATCH] fix missing includes 2005-10-30 17:37:32 -08:00
fs-writeback.c [PATCH] kernel-docs: fix kernel-doc format problems 2005-11-07 07:53:55 -08:00
inode.c [PATCH] fix nr_unused accounting, and avoid recursing in iput with I_WILL_FREE set 2005-10-30 17:37:26 -08:00
inotify.c [PATCH] inotify: add two inotify_add_watch flags 2005-12-12 08:57:43 -08:00
ioctl.c
ioprio.c fs/ioprio.c should #include <linux/syscalls.h> 2005-11-08 16:57:02 +01:00
Kconfig [PATCH] o Update Kconfig documentation to reflect support for readonly mounts. 2006-01-03 11:45:57 -08:00
Kconfig.binfmt [PATCH] frv: suppress configuration of certain features for FRV 2006-01-08 20:13:36 -08:00
libfs.c [PATCH] shrink dentry struct 2006-01-08 20:13:58 -08:00
locks.c NLM: Further cancel fixes 2006-01-06 14:58:54 -05:00
Makefile [PATCH] drop-pagecache 2006-01-08 20:12:40 -08:00
mbcache.c [PATCH] kfree cleanup: fs 2005-11-07 07:54:06 -08:00
mpage.c [PATCH] fix possible PAGE_CACHE_SHIFT overflows 2006-01-08 20:13:54 -08:00
namei.c [PATCH] Fix some problems with truncate and mtime semantics. 2006-01-08 20:13:52 -08:00
namespace.c [PATCH] shared mounts: cleanup 2006-01-08 20:13:56 -08:00
nfsctl.c
open.c [PATCH] Fix some problems with truncate and mtime semantics. 2006-01-08 20:13:52 -08:00
pipe.c [PATCH] sched: TASK_NONINTERACTIVE 2005-09-10 10:06:22 -07:00
pnode.c [PATCH] shared mounts: cleanup 2006-01-08 20:13:56 -08:00
pnode.h [PATCH] unbindable mounts 2005-11-07 18:18:11 -08:00
posix_acl.c [PATCH] gfp flags annotations - part 1 2005-10-08 15:00:57 -07:00
quota_v1.c
quota_v2.c
quota.c [PATCH] quota: small cleanups 2005-11-07 07:53:39 -08:00
read_write.c Relax the rw_verify_area() error checking. 2006-01-04 16:20:40 -08:00
readdir.c
select.c [PATCH] files: lock-free fd look-up 2005-09-09 13:57:55 -07:00
seq_file.c [PATCH] allow callers of seq_open do allocation themselves 2005-11-07 18:18:09 -08:00
stat.c
super.c [PATCH] remove mount/umount uevents from superblock handling 2006-01-04 16:18:07 -08:00
xattr_acl.c
xattr.c [PATCH] Fix listxattr() for generic security attributes 2005-12-12 08:57:42 -08:00