[lttng-dev] [RFC] Feedback on 2 development branches: wfstack and lfstack

[lttng-dev] [RFC] Feedback on 2 development branches: wfstack and lfstack

[Mathieu Desnoyers]

Hi!

I started modifying the stack APIs to reflect the changes we did for
wfcqueue, and also add pop_all() and iterators.

The volatile dev branches are available at:

http://git.dorsal.polymtl.ca/~compudj?p=userspace-rcu;a=shortlog;h=refs/heads/urcu/lfstack
or 
git://git.dorsal.polymtl.ca/~compudj/userspace-rcu
branch: urcu/lfstack

http://git.dorsal.polymtl.ca/~compudj?p=userspace-rcu;a=shortlog;h=refs/heads/urcu/wfstack
or
git://git.dorsal.polymtl.ca/~compudj/userspace-rcu
branch: urcu/wfstack

Sorry for not sending patches, I'm a bit time-constrained this weekend.
I am sending these links right away for review, because I think it might
be good to pull these commits into the master branch before we proceed
to other changes. And I want to minimize the amount of duplicated effort
between Lai and myself.

One of my next step will be to document the wfstack and lfstack APIs
more thoroughly (similarly to what we did for wfcqueue).

Then, my following step will be to see if I can implement a lfcqueue
API, derived from wfcqueue, but with lock-free enqueue semantic (a mix
of wfcqueue and rculfqueue).

Feedback is welcome!

Thanks,

Mathieu


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

[lttng-dev] [RFC] Feedback on 2 development branches: wfstack and lfstack

[Lai Jiangshan]

On 10/14/2012 02:12 AM, Mathieu Desnoyers wrote:
> Hi!
> 
> I started modifying the stack APIs to reflect the changes we did for
> wfcqueue, and also add pop_all() and iterators.
> 
> The volatile dev branches are available at:
> 
> http://git.dorsal.polymtl.ca/~compudj?p=userspace-rcu;a=shortlog;h=refs/heads/urcu/lfstack

I don't see the value of introducing struct cds_lfs_head.
It can force the users to use for_each() for the return value of pop_all().
Is it its purpose?

thr_dequeuer() of a8edcc02a25328647f91b4bbe8207e8cdfd317d3 is too complicated.
( I don't see the value of @counter)

do {
	...
	if (test_pop) {
		test_lfs_pop;
	}
	if (test_pop_all) {
		test_lfs_pop_all;
	}
	...
} while();





> or 
> git://git.dorsal.polymtl.ca/~compudj/userspace-rcu
> branch: urcu/lfstack
> 
> http://git.dorsal.polymtl.ca/~compudj?p=userspace-rcu;a=shortlog;h=refs/heads/urcu/wfstack
> or
> git://git.dorsal.polymtl.ca/~compudj/userspace-rcu
> branch: urcu/wfstack
> 
> Sorry for not sending patches, I'm a bit time-constrained this weekend.
> I am sending these links right away for review, because I think it might
> be good to pull these commits into the master branch before we proceed
> to other changes. And I want to minimize the amount of duplicated effort
> between Lai and myself.
> 
> One of my next step will be to document the wfstack and lfstack APIs
> more thoroughly (similarly to what we did for wfcqueue).
> 
> Then, my following step will be to see if I can implement a lfcqueue
> API, derived from wfcqueue, but with lock-free enqueue semantic (a mix
> of wfcqueue and rculfqueue).
> 
> Feedback is welcome!
> 
> Thanks,
> 
> Mathieu
> 
> 

[lttng-dev] [RFC] Feedback on 2 development branches: wfstack and lfstack

[Mathieu Desnoyers]

* Lai Jiangshan (laijs at cn.fujitsu.com) wrote:
> On 10/14/2012 02:12 AM, Mathieu Desnoyers wrote:
> > Hi!
> > 
> > I started modifying the stack APIs to reflect the changes we did for
> > wfcqueue, and also add pop_all() and iterators.
> > 
> > The volatile dev branches are available at:
> > 
> > http://git.dorsal.polymtl.ca/~compudj?p=userspace-rcu;a=shortlog;h=refs/heads/urcu/lfstack
> 
> I don't see the value of introducing struct cds_lfs_head.
> It can force the users to use for_each() for the return value of pop_all().
> Is it its purpose?

No exactly. The purpose of struct cds_lfs_head is to ensure that nobody
will attempt to use the for_each() iterators on struct cds_lfs_node
returned by __cds_lfs_pop(). I'm using typing to enforce usage
restrictions.

> 
> thr_dequeuer() of a8edcc02a25328647f91b4bbe8207e8cdfd317d3 is too complicated.
> ( I don't see the value of @counter)
> 
> do {
> 	...
> 	if (test_pop) {
> 		test_lfs_pop;
> 	}
> 	if (test_pop_all) {
> 		test_lfs_pop_all;
> 	}

I will refactor the duplicated code into functions.

The reason why I use a mask on a counter to select pop or pop all is to
ensure that we do the "loop_sleep(rduration)" delay equally for both pop
and pop_all. Moreover, it will be easier to change the rate of pop vs
pop_all in the future, using a randomization function rather than 50-50
chances.

The update for both lfs and wfs will be pushed shortly,

Thanks!

Mathieu

> 	...
> } while();
> 
> 
> 
> 
> 
> > or 
> > git://git.dorsal.polymtl.ca/~compudj/userspace-rcu
> > branch: urcu/lfstack
> > 
> > http://git.dorsal.polymtl.ca/~compudj?p=userspace-rcu;a=shortlog;h=refs/heads/urcu/wfstack
> > or
> > git://git.dorsal.polymtl.ca/~compudj/userspace-rcu
> > branch: urcu/wfstack
> > 
> > Sorry for not sending patches, I'm a bit time-constrained this weekend.
> > I am sending these links right away for review, because I think it might
> > be good to pull these commits into the master branch before we proceed
> > to other changes. And I want to minimize the amount of duplicated effort
> > between Lai and myself.
> > 
> > One of my next step will be to document the wfstack and lfstack APIs
> > more thoroughly (similarly to what we did for wfcqueue).
> > 
> > Then, my following step will be to see if I can implement a lfcqueue
> > API, derived from wfcqueue, but with lock-free enqueue semantic (a mix
> > of wfcqueue and rculfqueue).
> > 
> > Feedback is welcome!
> > 
> > Thanks,
> > 
> > Mathieu
> > 
> > 
> 

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