linux/net
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
..
802 [NET]: kfree cleanup 2005-11-08 09:41:34 -08:00
8021q [VLAN]: Add two missing checks to vlan_ioctl_handler() 2005-12-21 18:39:49 -08:00
appletalk [NET]: Add a dev_ioctl() fallback to sock_ioctl() 2006-01-03 14:18:33 -08:00
atm [NET]: Use newer is_multicast_ether_addr() in some files 2006-01-06 13:05:58 -08:00
ax25 [NET]: Add a dev_ioctl() fallback to sock_ioctl() 2006-01-03 14:18:33 -08:00
bluetooth Merge git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-2.6 2006-01-04 18:44:12 -08:00
bridge [BRIDGE] netfilter: vlan + hw checksum = bug? 2006-01-06 13:13:29 -08:00
core [NET]: Endian-annotate in_aton() 2006-01-06 13:24:54 -08:00
dccp [NETFILTER]: Handle NAT in IPsec policy checks 2006-01-07 12:57:37 -08:00
decnet [DECNET]: Only use local routers 2006-01-03 14:24:02 -08:00
econet [ECONET]: Use macro for spinlock_t definition. 2006-01-04 13:56:08 -08:00
ethernet [NET]: Use newer is_multicast_ether_addr() in some files 2006-01-06 13:05:58 -08:00
ieee80211 [IEEE80211] ipw2200: Simplify multicast checks. 2006-01-03 15:27:38 -08:00
ipv4 [IPV4]: make ip_fragment() static 2006-01-07 13:23:39 -08:00
ipv6 [PATCH] slab: remove unused align parameter from alloc_percpu 2006-01-08 20:12:39 -08:00
ipx [NET]: Add a dev_ioctl() fallback to sock_ioctl() 2006-01-03 14:18:33 -08:00
irda Merge git://git.kernel.org/pub/scm/linux/kernel/git/bunk/trivial 2006-01-04 16:34:57 -08:00
key [NET]: move struct proto_ops to const 2006-01-03 13:11:15 -08:00
lapb [NET]: Kill skb->list 2005-08-29 15:31:14 -07:00
llc [NET]: Add a dev_ioctl() fallback to sock_ioctl() 2006-01-03 14:18:33 -08:00
netfilter [NETFILTER]: Fix module_param types and permissions 2006-01-05 12:19:46 -08:00
netlink [NETLINK] genetlink: fix cmd type in genl_ops to be consistent to u8 2006-01-03 14:13:29 -08:00
netrom [NET]: Add a dev_ioctl() fallback to sock_ioctl() 2006-01-03 14:18:33 -08:00
packet [NET]: Add a dev_ioctl() fallback to sock_ioctl() 2006-01-03 14:18:33 -08:00
rose [NET]: Add a dev_ioctl() fallback to sock_ioctl() 2006-01-03 14:18:33 -08:00
rxrpc [NET]: Detect hardware rx checksum faults correctly 2005-11-10 13:01:24 -08:00
sched [INET_SOCK]: Move struct inet_sock & helper functions to net/inet_sock.h 2006-01-03 13:11:21 -08:00
sctp [NETFILTER]: Keep conntrack reference until IPsec policy checks are done 2006-01-07 12:57:36 -08:00
sunrpc [PATCH] shrink dentry struct 2006-01-08 20:13:58 -08:00
unix [NET]: Add a dev_ioctl() fallback to sock_ioctl() 2006-01-03 14:18:33 -08:00
wanrouter [NET]: Add a dev_ioctl() fallback to sock_ioctl() 2006-01-03 14:18:33 -08:00
x25 [X25]: Fix for broken x25 module. 2006-01-06 13:11:35 -08:00
xfrm [NETFILTER]: Handle NAT in IPsec policy checks 2006-01-07 12:57:37 -08:00
compat.c [PATCH] Fix 32bit sendmsg() flaw 2005-09-08 08:14:11 -07:00
Kconfig [NETFILTER] move nfnetlink options to right location in kconfig menu 2005-09-17 00:41:21 -07:00
Makefile [NETFILTER]: link 'netfilter' before ipv4 2005-11-14 15:25:59 -08:00
nonet.c [NET]: Fix sock_init() return value. 2006-01-03 13:11:17 -08:00
socket.c [NET]: Add a dev_ioctl() fallback to sock_ioctl() 2006-01-03 14:18:33 -08:00
sysctl_net.c [NET]: Fix "sysctl_net.c:36: error: 'core_table' undeclared here" 2005-10-03 14:16:34 -07:00
TUNABLE Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00