linux/ipc
Nick Piggin fa0d7e3de6 fs: icache RCU free inodes
RCU free the struct inode. This will allow:

- Subsequent store-free path walking patch. The inode must be consulted for
  permissions when walking, so an RCU inode reference is a must.
- sb_inode_list_lock to be moved inside i_lock because sb list walkers who want
  to take i_lock no longer need to take sb_inode_list_lock to walk the list in
  the first place. This will simplify and optimize locking.
- Could remove some nested trylock loops in dcache code
- Could potentially simplify things a bit in VM land. Do not need to take the
  page lock to follow page->mapping.

The downsides of this is the performance cost of using RCU. In a simple
creat/unlink microbenchmark, performance drops by about 10% due to inability to
reuse cache-hot slab objects. As iterations increase and RCU freeing starts
kicking over, this increases to about 20%.

In cases where inode lifetimes are longer (ie. many inodes may be allocated
during the average life span of a single inode), a lot of this cache reuse is
not applicable, so the regression caused by this patch is smaller.

The cache-hot regression could largely be avoided by using SLAB_DESTROY_BY_RCU,
however this adds some complexity to list walking and store-free path walking,
so I prefer to implement this at a later date, if it is shown to be a win in
real situations. I haven't found a regression in any non-micro benchmark so I
doubt it will be a problem.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-07 17:50:26 +11:00
..
Makefile Add generic sys_ipc wrapper 2010-03-12 15:52:32 -08:00
compat.c ipc: initialize structure memory to zero for compat functions 2010-10-27 18:03:13 -07:00
compat_mq.c ipc: initialize structure memory to zero for compat functions 2010-10-27 18:03:13 -07:00
ipc_sysctl.c sysctl ipc: Remove dead binary sysctl support code. 2009-11-12 02:04:54 -08:00
ipcns_notifier.c
mq_sysctl.c sysctl ipc: Remove dead binary sysctl support code. 2009-11-12 02:04:54 -08:00
mqueue.c fs: icache RCU free inodes 2011-01-07 17:50:26 +11:00
msg.c kernel-wide: replace USHORT_MAX, SHORT_MAX and SHORT_MIN with USHRT_MAX, SHRT_MAX and SHRT_MIN 2010-05-25 08:07:02 -07:00
msgutil.c namespaces: ipc namespaces: implement support for posix msqueues 2009-04-07 08:31:09 -07:00
namespace.c ipcns: make free_ipc_ns() static 2009-06-18 13:03:56 -07:00
sem.c sys_semctl: fix kernel stack leakage 2010-10-01 10:50:58 -07:00
shm.c ipc: shm: fix information leak to userland 2010-10-30 08:25:51 -07:00
syscall.c ppc64 sys_ipc breakage in 2.6.34-rc2 2010-03-22 09:57:19 -07:00
util.c kernel-wide: replace USHORT_MAX, SHORT_MAX and SHORT_MIN with USHRT_MAX, SHRT_MAX and SHRT_MIN 2010-05-25 08:07:02 -07:00
util.h ipc: unbreak 32-bit shmctl/semctl/msgctl 2009-06-21 12:48:43 -07:00