Re: [PATCH 1/3] writeback: simplify the write back thread queue

[Artem Bityutskiy <dedekind1@gmail.com>]

On Sat, 2010-06-19 at 23:07 +0200, Christoph Hellwig wrote:
> First remove items from work_list as soon as we start working on them.  This
> means we don't have to track any pending or visited state and can get
> rid of all the RCU magic freeing the work items - we can simply free
> them once the operation has finished.  Second use a real completion for
> tracking synchronous requests - if the caller sets the completion pointer
> we complete it, otherwise use it as a boolean indicator that we can free
> the work item directly.  Third unify struct wb_writeback_args and struct
> bdi_work into a single data structure, wb_writeback_work.  Previous we
> set all parameters into a struct wb_writeback_args, copied it into
> struct bdi_work, copied it again on the stack to use it there.  Instead
> of just allocate one structure dynamically or on the stack and use it
> all the way through the stack.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Christoph, thanks for simplifying this. I wonder also, why do we need
the bdi_pending_list - for me it looks redundant.

Also, do we need the forker task? It hurts because it wakes up every 5
sec jut to check whether it has to fork something and to waste the
battery energy. Do we really need to bdi threads to kill themselves
after 5 minutes of inactivity?

I'm going to work on optimizing the forker per-bdi threads wake-ups. But
for the forker - it seems it is better to just get rid of it completely.
Jens, what do you think?

-- 
Best Regards,
Artem Bityutskiy (Артём Битюцкий)

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