On Wed, 2013-03-20 at 15:55 -0400, Rik van Riel wrote: > Introduce finer grained locking for semtimedop, to handle the > common case of a program wanting to manipulate one semaphore > from an array with multiple semaphores. > > If the call is a semop manipulating just one semaphore in > an array with multiple semaphores, only take the lock for > that semaphore itself. > > If the call needs to manipulate multiple semaphores, or > another caller is in a transaction that manipulates multiple > semaphores, the sem_array lock is taken, as well as all the > locks for the individual semaphores. > > 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 > > Signed-off-by: Rik van Riel <r...@redhat.com> > Suggested-by: Linus Torvalds <torva...@linux-foundation.org>
Acked-by: Davidlohr Bueso <davidlohr.bu...@hp.com> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
