[PATCH 00/11] sysv ipc shared mem optimizations

From: Davidlohr Bueso
Date: Tue Jun 18 2013 - 21:18:52 EST

This is the third and final patchset that deals with reducing the
amount of contention we impose on the ipc lock (kern_ipc_perm.lock).
These changes mostly deal with shared memory, previous work has already
been done for semaphores and message queues:

http://lkml.org/lkml/2013/3/20/546 (sems)
http://lkml.org/lkml/2013/5/15/584 (mqueues)

With these patches applied, a custom shm microbenchmark stressing shmctl
doing IPC_STAT with 4 threads a million times, reduces the execution time by 50%.
A similar run, this time with IPC_SET, reduces the execution time from 3 mins and
35 secs to 27 seconds.

Patches 1-8: replaces blindly taking the ipc lock for a smarter combination
of rcu and ipc_obtain_object, only acquiring the spinlock when updating.

Patch 9: renames the ids rw_mutex to rwsem, which is what it already was.

Patch 10: is a trivial mqueue leftover cleanup

Patch 11: adds a brief lock scheme description, requested by Andrew.

This patchset applies on top of linux-next (3.10.0-rc6-next-20130618).

Davidlohr Bueso (11):
ipc,shm: introduce lockless functions to obtain the ipc object
ipc,shm: shorten critical region in shmctl_down
ipc: drop ipcctl_pre_down
ipc,shm: introduce shmctl_nolock
ipc,shm: make shmctl_nolock lockless
ipc,shm: shorten critical region for shmctl
ipc,shm: cleanup do_shmat pasta
ipc,shm: shorten critical region for shmat
ipc: rename ids->rw_mutex
ipc,msg: drop msg_unlock
ipc: document general ipc locking scheme

include/linux/ipc_namespace.h | 2 +-
ipc/msg.c | 25 +++--
ipc/namespace.c | 4 +-
ipc/sem.c | 24 ++---
ipc/shm.c | 239 ++++++++++++++++++++++++++----------------
ipc/util.c | 57 +++++-----
ipc/util.h | 7 +-
7 files changed, 199 insertions(+), 159 deletions(-)


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