Re: [PATCH, RFC] simplify writeback thread creation

[Jens Axboe <axboe@kernel.dk>]

On 2010-07-08 00:52, Christoph Hellwig wrote:
> Currently the per-bdi writeback thread is only created when there is
> dirty any dirty data on the BDI, and it lazy exists when it's been
> unused for some time.
> 
> This leads to some very complex code, and the need to keep a forker
> thread around.
> 
> This patch removes all this code and simply creates the thread as part
> of the bdi registration.  The downside is that we use up ressoures
> for possible unused devices, although that overhead is rather low,
> with 8k kernel stack size on x86 and few other, even smaller ressources.
> 
> If the overhead is still considered too much I can look into starting
> the thread explicitly instead of as part of the bdi registration, but
> that will require a bit of code complexity, too.

I'm pretty sure this will come back to bite us in the ass... If we are
going to change the lazy create/exit setup, I would greatly prefer
doing it at fs mount time (or something to that effect).

-- 
Jens Axboe