Re: [PATCH 12/12] vmscan: Do not writeback pages in direct reclaim

[Rik van Riel]

On 06/15/2010 09:59 AM, Mel Gorman wrote:
> On Tue, Jun 15, 2010 at 09:34:18AM -0400, Rik van Riel wrote:
> > On 06/15/2010 07:45 AM, Mel Gorman wrote:

> > > > > +/* kswapd and memcg can writeback as they are unlikely to overflow stack */
> > > > > +static inline bool reclaim_can_writeback(struct scan_control *sc)
> > > > > +{
> > > > > +	return current_is_kswapd() || sc->mem_cgroup != NULL;
> > > > > +}

> > If direct reclaim can overflow the stack, so can direct
> > memcg reclaim.  That means this patch does not solve the
> > stack overflow, while admitting that we do need the
> > ability to get specific pages flushed to disk from the
> > pageout code.
>
> What path is taken with memcg != NULL that could overflow the stack? I
> couldn't spot one but mm/memcontrol.c is a bit tangled so finding all
> its use cases is tricky. The critical path I had in mind though was
> direct reclaim and for that path, memcg == NULL or did I miss something?

mem_cgroup_hierarchical_reclaim -> try_to_free_mem_cgroup_pages

--
All rights reversed
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/