summaryrefslogtreecommitdiff
path: root/ipc
diff options
context:
space:
mode:
authorDavidlohr Bueso <davidlohr.bueso@hp.com>2013-04-30 19:15:14 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-05-01 08:12:57 -0700
commit7bb4deff61bdab3338534841cb6d0508314a41d6 (patch)
tree2a3be8bf66313a085b9e7c084bbcee5cad8a9b2a /ipc
parent1e3c941c52eab70c8acb2f77829c24673445c858 (diff)
downloadkernel-7bb4deff61bdab3338534841cb6d0508314a41d6.tar.gz
ipc: remove bogus lock comment for ipc_checkid
This series makes the sysv semaphore code more scalable, by reducing the time the semaphore lock is held, and making the locking more scalable for semaphore arrays with multiple semaphores. The first four patches were written by Davidlohr Buesso, and reduce the hold time of the semaphore lock. The last three patches change the sysv semaphore code locking to be more fine grained, providing a performance boost when multiple semaphores in a semaphore array are being manipulated simultaneously. On a 24 CPU system, performance numbers with the semop-multi test with N threads and N semaphores, look like this: vanilla Davidlohr's Davidlohr's + Davidlohr's + threads patches rwlock patches v3 patches 10 610652 726325 1783589 2142206 20 341570 365699 1520453 1977878 30 288102 307037 1498167 2037995 40 290714 305955 1612665 2256484 50 288620 312890 1733453 2650292 60 289987 306043 1649360 2388008 70 291298 306347 1723167 2717486 80 290948 305662 1729545 2763582 90 290996 306680 1736021 2757524 100 292243 306700 1773700 3059159 This patch: There is no reason to be holding the ipc lock while reading ipcp->seq, hence remove misleading comment. Also simplify the return value for the function. Signed-off-by: Davidlohr Bueso <davidlohr.bueso@hp.com> Signed-off-by: Rik van Riel <riel@redhat.com> Cc: Chegu Vinod <chegu_vinod@hp.com> Cc: Emmanuel Benisty <benisty.e@gmail.com> Cc: Jason Low <jason.low2@hp.com> Cc: Michel Lespinasse <walken@google.com> Cc: Peter Hurley <peter@hurleysoftware.com> Cc: Stanislav Kinsbursky <skinsbursky@parallels.com> Tested-by: Sedat Dilek <sedat.dilek@gmail.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/util.h7
1 files changed, 1 insertions, 6 deletions
diff --git a/ipc/util.h b/ipc/util.h
index eeb79a1fbd83..ac1480a4efd1 100644
--- a/ipc/util.h
+++ b/ipc/util.h
@@ -150,14 +150,9 @@ static inline int ipc_buildid(int id, int seq)
return SEQ_MULTIPLIER * seq + id;
}
-/*
- * Must be called with ipcp locked
- */
static inline int ipc_checkid(struct kern_ipc_perm *ipcp, int uid)
{
- if (uid / SEQ_MULTIPLIER != ipcp->seq)
- return 1;
- return 0;
+ return uid / SEQ_MULTIPLIER != ipcp->seq;
}
static inline void ipc_lock_by_ptr(struct kern_ipc_perm *perm)