aboutsummaryrefslogtreecommitdiff
path: root/ipc
diff options
context:
space:
mode:
authorDavidlohr Bueso <davidlohr.bueso@hp.com>2013-09-11 14:26:15 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-09-11 15:59:38 -0700
commit8b8d52ac382b17a19906b930cd69e2edb0aca8ba (patch)
tree19c4c3afbb5c349e9a6ee570c7dd10c73d2f4a90 /ipc
parent6e19eded3684dc184181093af3bff2ff440f5b53 (diff)
downloadlinux-8b8d52ac382b17a19906b930cd69e2edb0aca8ba.tar.gz
ipc,shm: introduce lockless functions to obtain the ipc object
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 patch: Add shm_obtain_object() and shm_obtain_object_check(), which will allow us to get the ipc object without acquiring the lock. Just as with other forms of ipc, these functions are basically wrappers around ipc_obtain_object*(). Signed-off-by: Davidlohr Bueso <davidlohr.bueso@hp.com> Tested-by: Sedat Dilek <sedat.dilek@gmail.com> Cc: Rik van Riel <riel@redhat.com> Cc: Manfred Spraul <manfred@colorfullife.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'ipc')
-rw-r--r--ipc/shm.c20
1 files changed, 20 insertions, 0 deletions
diff --git a/ipc/shm.c b/ipc/shm.c
index c6b4ad5ce3b..216ae727a93 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -124,6 +124,26 @@ void __init shm_init (void)
IPC_SHM_IDS, sysvipc_shm_proc_show);
}
+static inline struct shmid_kernel *shm_obtain_object(struct ipc_namespace *ns, int id)
+{
+ struct kern_ipc_perm *ipcp = ipc_obtain_object(&shm_ids(ns), id);
+
+ if (IS_ERR(ipcp))
+ return ERR_CAST(ipcp);
+
+ return container_of(ipcp, struct shmid_kernel, shm_perm);
+}
+
+static inline struct shmid_kernel *shm_obtain_object_check(struct ipc_namespace *ns, int id)
+{
+ struct kern_ipc_perm *ipcp = ipc_obtain_object_check(&shm_ids(ns), id);
+
+ if (IS_ERR(ipcp))
+ return ERR_CAST(ipcp);
+
+ return container_of(ipcp, struct shmid_kernel, shm_perm);
+}
+
/*
* shm_lock_(check_) routines are called in the paths where the rw_mutex
* is not necessarily held.