linux/drivers/usb/core
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
..
buffer.c [PATCH] USB: don't allocate dma pools for PIO HCDs 2006-01-04 13:51:39 -08:00
config.c [PATCH] USB: move CONFIG_USB_DEBUG checks into the Makefile 2005-11-17 11:29:55 -08:00
devices.c [PATCH] USB: mark various usb tables const 2006-01-04 13:51:40 -08:00
devio.c [PATCH] USB: Remove USB private semaphore 2006-01-04 13:48:34 -08:00
driver.c [PATCH] USB: Remove USB private semaphore 2006-01-04 13:48:34 -08:00
file.c [PATCH] USB: move CONFIG_USB_DEBUG checks into the Makefile 2005-11-17 11:29:55 -08:00
hcd-pci.c [PATCH] USB: Fix USB suspend/resume crasher (#2) 2005-11-29 21:39:23 -08:00
hcd.c [PATCH] USB: Consider power budget when choosing configuration 2006-01-04 13:48:34 -08:00
hcd.h [PATCH] USB: central handling for host controllers that were reset during suspend/resume 2006-01-04 13:48:31 -08:00
hub.c [PATCH] USB: Don't assume root-hub resume succeeds 2006-01-04 13:51:40 -08:00
hub.h [PATCH] USB: Consider power budget when choosing configuration 2006-01-04 13:48:34 -08:00
inode.c [PATCH] shrink dentry struct 2006-01-08 20:13:58 -08:00
Kconfig [PATCH] root hub updates (greater half) 2005-10-28 16:47:40 -07:00
Makefile [PATCH] USB: reorg some functions out of the main usb.c file 2006-01-04 13:48:31 -08:00
message.c [PATCH] USB: fix local variable clash 2006-01-04 13:51:42 -08:00
notify.c [PATCH] USB: move CONFIG_USB_DEBUG checks into the Makefile 2005-11-17 11:29:55 -08:00
otg_whitelist.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
sysfs.c [PATCH] USB: move CONFIG_USB_DEBUG checks into the Makefile 2005-11-17 11:29:55 -08:00
urb.c [PATCH] USB: move CONFIG_USB_DEBUG checks into the Makefile 2005-11-17 11:29:55 -08:00
usb.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-2.6 2006-01-04 18:44:12 -08:00
usb.h [PATCH] USB: Remove USB private semaphore 2006-01-04 13:48:34 -08:00