6062a8dc05
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
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| .. | ||
| compat.c | ||
| compat_mq.c | ||
| ipc_sysctl.c | ||
| ipcns_notifier.c | ||
| Makefile | ||
| mq_sysctl.c | ||
| mqueue.c | ||
| msg.c | ||
| msgutil.c | ||
| namespace.c | ||
| sem.c | ||
| shm.c | ||
| syscall.c | ||
| util.c | ||
| util.h | ||