Re: [RFC][PATCH] create workqueue threads only when needed

[Ingo Molnar <mingo@elte.hu>]

* Frederic Weisbecker <fweisbec@gmail.com> wrote:

> On Tue, Jan 27, 2009 at 03:07:27AM +0000, Alasdair G Kergon wrote:
> > On Tue, Jan 27, 2009 at 01:17:11AM +0100, Frederic Weisbecker wrote:
> > > For several reasons:
> > > _ Unneeded built drivers for my system that create workqueue(s) when they init
> > > _ Services which need their own workqueue, for several reasons, but who receive
> > >   very rare jobs (often never)
> > 
> > > I hadn't any problems until now with this patch but I think it needs more testing,
> > > like with cpu hotplug, and some renaming for its functions and structures...
> > > And I would like to receive some comments and feelings before continuing. So this
> > > is just an RFC :-)
> > 
> > Make sure this optimisation also works when the system's running low 
> > on memory if workqueues are involved in "making forward progress".  
> > Doubtless there are other reasons for apparently-unused workqueues 
> > too.
> 
> That's true. But currently, each useless workqueue thread is consuming a 
> task_struct in memory, so this patch makes actually consuming less 
> memory than before. If the system is running low on memory...well 
> perhaps I can reschedule the thread creation after some delays...?

Lets put a warning in there to make sure it's not forgotten - and deal 
with it if it happens.

	Ingo