Re: [Boost-users] Shared mutex vs normal mutex

26 Aug 2009

      Guys,
I know my question is long, but it is actually very simple. It can be
summarized as: "Have you used shared_mutex and shared_locks and have you
seen an improvement against regular locks?"

Thanks, any comments appreciated

Alessandro

On Aug 25, 2009, at 7:27 AM, Alessandro Bellina  wrote:
...
Hello
I am testing the boost mutex/lock classes in order to implement a multiple
reader single writer model.
Because of this I thought that the shared mutex with lock_shared and
lock_unique would be perfect. I'm finding that the performance is no better
than with a simple mutex.
My writer is adding a bunch of elements, locking the shared container
exclusivelly until it is done.  The readers looks at all elements of the
container, locking on a per element basis.
Any ideas as to why the shared mutex would be slower in this case than the
simple mutex?
This is the code for my producer thread and my consumers (as a side note,
employee_set is a multi index):
typedef boost::shared_mutex mutex_type;
typedef boost::shared_lock read_lock_type;
typedef boost::unique_lock write_lock_type;
static mutex_type rw_mutex;
 struct ConsumerThread{
ConsumerThread (employee_set* e):es(e){}
 void operator()(){
 for (int i=0; i<es->size(); i++){
read_lock_type l(rw_mutex);
es->get<1>();
}
 }
 employee_set* es;
 };
struct ProducerThread{
 ProducerThread(int n, employee_set* e):N(n),es(e){}
 void operator()(){
 write_lock_type l(rw_mutex);
for (int i=0; iinsert (employee(i, "TestEmployee",100-i));
}
l.unlock();
 }
 int N;
employee_set* es;
};