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From: Mel Gorman on 15 Jun 2010 12:00
On Tue, Jun 15, 2010 at 06:47:01AM -0400, Christoph Hellwig wrote:
> On Mon, Jun 14, 2010 at 12:17:49PM +0100, Mel Gorman wrote:
> > /*
> > + * TODO: Try merging with migrations version of putback_lru_pages
> > + */
> > +static noinline_for_stack void putback_lru_pages(struct zone *zone,
> > + struct zone_reclaim_stat *reclaim_stat,
> > + unsigned long nr_anon, unsigned long nr_file,
> > + struct list_head *page_list)
> > +{
>
> I hate to nitpick on this, but with noinline_for_stack a prototype
> really is unreadbale unless the function identifier goes to the next
> line. Compare the one above with:
>
> static noinline_for_stack void
> putback_lru_pages(struct zone *zone, struct zone_reclaim_stat *reclaim_stat,
> unsigned long nr_anon, unsigned long nr_file,
> struct list_head *page_list)
>
> > -static unsigned long shrink_inactive_list(unsigned long nr_to_scan,
> > +static noinline_for_stack unsigned long shrink_inactive_list(unsigned long nr_to_scan,
> > struct zone *zone, struct scan_control *sc,
> > int priority, int file)
>
> Same here, just even worse due to the spill over ove 80 characters.
>

It's a fair nitpick and so is cleaned up.

--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
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From: Mel Gorman on 17 Jun 2010 06:40
On Wed, Jun 16, 2010 at 04:43:09PM -0700, Andrew Morton wrote:
> On Mon, 14 Jun 2010 12:17:49 +0100
> Mel Gorman <mel(a)csn.ul.ie> wrote:
>
> > shrink_inactive_list() sets up a pagevec to release unfreeable pages. It
> > uses significant amounts of stack doing this. This patch splits
> > shrink_inactive_list() to take the stack usage out of the main path so
> > that callers to writepage() do not contain an unused pagevec on the
> > stack.
>
> You can get the entire pagevec off the stack - just make it a
> static-to-shrink_inactive_list() pagevec-per-cpu.
>

That idea has been floated as well. I didn't pursue it because Dave
said that giving page reclaim a stack diet was never going to be the
full solution so I didn't think the complexity was justified.

I kept some of the stack reduction stuff because a) it was there and b)
it would give kswapd extra headroom when calling writepage.

> Locking just requires pinning to a CPU. We could trivially co-opt
> shrink_inactive_list()'s spin_lock_irq() for that, but
> pagevec_release() can be relatively expensive so it'd be sad to move
> that inside spin_lock_irq(). It'd be better to slap a
> get_cpu()/put_cpu() around the whole thing.
>

It'd be something interesting to try out when nothing else was happening but
I'm not going to focus on it for the moment unless I think it will really
help this stack overflow problem.

--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
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