linux/net/sunrpc
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
..
auth_gss SUNRPC: Make krb5 report unsupported encryption types 2006-01-06 14:59:00 -05:00
Makefile [PATCH] RPC: introduce client-side transport switch 2005-09-23 12:38:12 -04:00
auth.c NFS,SUNRPC,NLM: fix unused variable warnings when CONFIG_SYSCTL is disabled 2005-11-04 15:39:48 -05:00
auth_null.c [PATCH] RPC: Eliminate socket.h includes in RPC client 2005-09-23 12:38:23 -04:00
auth_unix.c [PATCH] RPC: Eliminate socket.h includes in RPC client 2005-09-23 12:38:23 -04:00
cache.c [PATCH] sunrpc: cache_register can use wrong module reference 2005-09-07 16:57:25 -07:00
clnt.c SUNRPC: get rid of cl_chatty 2006-01-06 14:58:56 -05:00
pmap_clnt.c SUNRPC: get rid of cl_chatty 2006-01-06 14:58:56 -05:00
rpc_pipe.c [PATCH] shrink dentry struct 2006-01-08 20:13:58 -08:00
sched.c SUNRPC: switchable buffer allocation 2006-01-06 14:58:55 -05:00
socklib.c [NET]: Detect hardware rx checksum faults correctly 2005-11-10 13:01:24 -08:00
stats.c [PATCH] sunrpc: print unsigned integers in stats 2005-09-07 16:57:39 -07:00
sunrpc_syms.c SUNRPC: Get rid of some unused exports 2006-01-06 14:58:41 -05:00
svc.c [NET]: kfree cleanup 2005-11-08 09:41:34 -08:00
svcauth.c [PATCH] sunrpc: cache_register can use wrong module reference 2005-09-07 16:57:25 -07:00
svcauth_unix.c [PATCH] knfsd: fix hash function for IP addresses on 64bit little-endian machines. 2006-01-06 08:33:21 -08:00
svcsock.c [PATCH] Keep nfsd from exiting when seeing recv() errors 2006-01-06 08:33:59 -08:00
sysctl.c SUNRPC: allow sunrpc.o to link when CONFIG_SYSCTL is disabled 2005-11-04 15:39:45 -05:00
timer.c Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
xdr.c SUNRPC: net/sunrpc/xdr.c: remove xdr_decode_string() 2006-01-06 14:58:53 -05:00
xprt.c SUNRPC: Clean up xprt_destroy() 2006-01-06 14:58:58 -05:00
xprtsock.c SUNRPC: Ensure client closes the socket when server initiates a close 2006-01-06 14:58:57 -05:00