Re: [PATCH 0/3] Convert libata pio task to slow-work

[Jens Axboe <jens.axboe@oracle.com>]

On Fri, Aug 28 2009, Tejun Heo wrote:
> >>> Care to post it? I know you don't think it's perfect yet, but it would
> >>> make a lot more sense to throw effort into this rather than waste time
> >>> on partial solutions.
> >> I have this printed out code with full of red markings from proof
> >> reading and flush implementation is mostly broken.  Please give me a
> >> couple of days.  I'll post a rough unsplit version which at least
> >> compiles with the planned changes applied by the end of the week.  :-)
> > 
> > Alright, fair enough.
> > 
> > One question - do the 'exposed' workqueues (the ones that drivers
> > allocate/create) sitting in front of the global cpu queue allow more
> > than one thread per cpu, or is that property retained for the global cpu
> > queue (where it is a necessity)?
> 
> The exposed workqueues basically just play the gateway and don't have
> threads associated with it, well, at least not the normal ones.  It
> may have single dedicated thread which usually isn't used but only
> gets summoned when a queue stall is detected (new thread needs to be
> created but blocks on allocation kind of situation).  So, only the
> global cpu queue has normal workers and there are multiple per cpu and
> they're shared by all exported workqueues.

Thanks for the clarification, it answers the question on what level of
functionality is observed by the exported workqueues. Sounds good!

-- 
Jens Axboe