Changes between Version 12 and Version 13 of user_synchro

Timestamp:

Oct 10, 2018, 11:31:31 AM (6 years ago)

Author:

alain

Comment:

--

user_synchro

@@ -56 +56 @@
 
 For each user barrier, ALMOS-MKH creates a kernel ''remote_barrier_t'' structure, dynamically allocated in the reference cluster (i.e. in the cluster containing the reference process descriptor).
- * The '''remote_barrier_create()''' function allocates and initializes a barrier, using an RPC if if the calling thread is not running in the reference cluster.
+ * The '''remote_barrier_create()''' function allocates and initializes a barrier, to define the number of expected threads, using an RPC if if the calling thread is not running in the reference cluster.
  * The '''remote_barrier_destroy()''' function destroys a given barrier, using RPC if the calling thread is not running in the reference cluster. 
- * The blocking '''remote_barrier_wait()''' function returns only when all expected threads (defined by the remote_barrier_create() function) reach the barrier. It implement a descheduling policy: when a thread is not the last expected thread, it register in he barrier waiting queue and blocks on the THREAD_BLOCKED_USERSYNC condition. The last thread reset the barrier and unblocks all waiting threads.
+ * The blocking '''remote_barrier_wait()''' function returns only when all expected threads reach the barrier. It implements a descheduling policy: when a thread is not the last expected thread, it register in he barrier waiting queue and blocks on the THREAD_BLOCKED_USERSYNC condition. The last thread reset the barrier and unblocks all waiting threads.
+
+N.B. ''In the current implementation, the barrier is physically implemented in the reference cluster, creating contention when the
+number of threads is large. It exists a distributed implementation, where the barrier is implemented as a quad-tree, entirely  in user space (no system calls)''.
 
 == E) Semaphore ==