[lttng-dev] [URCU PATCH 1/3] wfcqueue: implement concurrency-efficient queue

[Mathieu Desnoyers]

* Lai Jiangshan (laijs at cn.fujitsu.com) wrote:
> On 10/02/2012 10:14 PM, Mathieu Desnoyers wrote:
[...]
> > --- /dev/null
> > +++ b/urcu/wfcqueue.h
> > @@ -0,0 +1,263 @@
> > +#ifndef _URCU_WFCQUEUE_H
> > +#define _URCU_WFCQUEUE_H
> > +
> > +/*
> > + * wfcqueue.h
> > + *
> > + * Userspace RCU library - Concurrent Queue with Wait-Free Enqueue/Blocking Dequeue
> > + *
> > + * Copyright 2010-2012 - Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
> > + * Copyright 2011-2012 - Lai Jiangshan <laijs at cn.fujitsu.com>
> > + *
> > + * This library is free software; you can redistribute it and/or
> > + * modify it under the terms of the GNU Lesser General Public
> > + * License as published by the Free Software Foundation; either
> > + * version 2.1 of the License, or (at your option) any later version.
> > + *
> > + * This library is distributed in the hope that it will be useful,
> > + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> > + * Lesser General Public License for more details.
> > + *
> > + * You should have received a copy of the GNU Lesser General Public
> > + * License along with this library; if not, write to the Free Software
> > + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
> > + */
> > +
> > +#include <pthread.h>
> > +#include <assert.h>
> > +#include <stdbool.h>
> > +#include <urcu/compiler.h>
> > +#include <urcu/arch.h>
> > +
> > +#ifdef __cplusplus
> > +extern "C" {
> > +#endif
> > +
> > +/*
> > + * Concurrent queue with wait-free enqueue/blocking dequeue.
> > + *
> > + * Inspired from half-wait-free/half-blocking queue implementation done by
> > + * Paul E. McKenney.
> > + */
> > +
> > +struct cds_wfcq_node {
> > +	struct cds_wfcq_node *next;
> > +};
> > +
> > +/*
> > + * Do not put head and tail on the same cache-line if concurrent
> > + * enqueue/dequeue are expected from many CPUs. This eliminates
> > + * false-sharing between enqueue and dequeue.
> > + */
> > +struct cds_wfcq_head {
> > +	struct cds_wfcq_node node;
> > +	pthread_mutex_t lock;
> > +};
> > +
> > +struct cds_wfcq_tail {
> > +	struct cds_wfcq_node *p;
> > +};
> 
> Why use "p" here?

For lack of imagination. ;)  Do you have something better to propose ?

> 
> I don't see the commits in the public git-tree. Or you forgot to update the
> tree and make "http" address happy.

I have pushed those into the userspace RCU master branch a couple of
days after posting them to the mailing lists. I just synchronized my
urcu/wfcqueue volatile dev branch, but I expect to drop it soon, since
it's now merged back into master.

Thanks!

Mathieu

> 
> Thanks,
> Lai

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com