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

Subject: Re: [Boost-users] Shared mutex vs normal mutex
From: Alessandro Bellina (abellina_at_[hidden])
Date: 2009-08-26 13:10:23

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 <abellina_at_[hidden]> 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<mutex_type> read_lock_type;
> typedef boost::unique_lock<mutex_type> 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; i<N; i++){
> es->insert (employee(i, "TestEmployee",100-i));
> }
> l.unlock();
>  }
>  int N;
> employee_set* es;
> };
>
>
>